DISEASES OF THE EYE I. Examination of the Eyes In the course of an examination of animals for soundness by a veterinary surgeon, prior to purchase by a client, the examination of the eyes is an important item. This is especially so in the case of the horse, and particularly with regard to hunters and thoroughbreds, in which, failing a full certificate of soundness, one of soundness"in eyes and wind"is a material factor in determining the value of the horse.
Good sight and sound eyes are important in all horses used for riding purposes, thorough breds especially, 'chasers, hunters, Aftiy rides, and hacks; and also in horses driven in single harness. Similarly in sporting dogs sound eyes are essential, and blindness is in all cases a dis qualification under Kennel Club Rules.
The first serious inspection of the eyes is made when the horse is pulled up after his gallop for testing the wind. The gallop has the effect of dilating the pupil, so allowing a better inspection of the lens.
The horse should be made to stand in a shady place such as an archway so that direct sunlight does not fall on the eyes, the best light being the diffuse light reflected from white clouds. The examiner should be provided with a dull black cloth-covered disc or shield with which to inter cept bright light-rays, which cause reflections on the moist glistening transparent cornea, so inter fering with a distinct view of the various structures in the eye. It is advisable to make sure that no windows or other possible reflecting surfaces are in such a position as to throw images into the eyes or non-existent cataracts may be certified to and a sound horse condemned.
The eyelids are first inspected for the detec tion of old wounds or injuries likely to interfere with the lachrymal drainage, for puckering or inversion (entropion), or for angular bends in the lid marginal curve—a frequent sign of old periodic ophthalmia—or for any tumours or cysts. The membrana nictitans is observed particularly to determine the presence of in cipient or small tumours, and incidentally to detect any sign of tetanus infection, particularly in recently - docked horses. The conjunctiva will indicate the presence of jaundice, or pur pura, or circulatory disturbance.
Attention is then concentrated on the eye as the organ of sight. The cornea is carefully inspected for opacities which, if large and dense are at once detected, but if speck-like, or linear, or very thin and filmy are seen only in certain positions and after thorough search. Such small opacities are unsoundness in the technical sense, and will upset a warranty of soundness. The experienced examiner will, however, exercise his judgment, discriminating between recent thin blue nebulm—such as result from a flick with a whiplash, and capable of rapid absorption— and dense vascularized old scars. Opacities over the pupillary area will obviously receive more consideration than those close to the limbus. Such partial opacities as are central and likely to cause irregular refraction and duplication of images, so predisposing to shying or to misjudging fences, will be most serious of all. With any recent injury it is important to determine the presence of a wound or ulcer, if necessary by the use of fluorescein solution, since any loss of surface cells must be considered a potential entrance for infection and serious eye disease. In such a case the certificate may be withheld till the defect has had time to heal. The anterior chamber should contain only clear aqueous humour, so allowing an uninterrupted view of the iris. Any turbidity of the aqueous humour, or any deposit of lymph in the floor of the chamber, is a very serious defect pointing to previous ophthalmia. The iris should be in spected as to its lustre, uniformity of colour, the evenness of its pupillary margin, and the entire absence of any raggedness, and for motility when alternately stimulated by bright light and shaded. Abnormalities in these directions point to previous attacks of iritis (q.v.). Depending from the upper part of the pupillary margin of the iris are two or more brownish-black bodies of more or less spherical shape—the corpora nigra. Sometimes these are of excessive size— a defect worth mention.
The pupil should be observed to contract and dilate according to the degree of illumination, a permanently dilated pupil pointing to optic nerve defects, a contracted one suggesting iritis, and a pupil with ragged, uneven margin indicat ing some tying down of the iris to either the lens or the cornea as a result of old iritis.
The lens should receive particular attention in order to determine the presence or absence of cataract. With a large cataract involving the whole or a good part of the lens, dense, white, and woolly, there is no difficulty. The horse is blind in that eye, and all the symptoms and signs are obvious. With a small speck less than a pin's-head and not necessarily in the centre of the lens considerable care has to be taken in its detection. In a moderate diffused light and with a well-dilated pupil the ordinary naked eye examination is in most cases sufficient, but with a contracted pupil it is impossible to say whether there are specks in the lens or not.
Special methods of examination must then be used, and since these are of use in connection with the diagnosis, prognosis, and treatment of various eye diseases they will be described in general terms, the reader applying as much as is necessary to the examination for soundness only.
Focal or Oblique Illumination.This method is used for the examination of the conjunctiva, cornea, sclerotic, and iris—in other words, for the anterior parts of the eye. It is especially useful for the detection of foreign bodies, and of injuries to or ulcers of the cornea.
Light, whether from a lamp in the dark-room, or in daylight, is focussed on to the eye by means of a double convex lens. The usual lens is one of about + 14 D i (such as is usually supplied with the ophthalmoscope). An ordinary reading glass will answer the same purpose. The lens is placed with its principal axis in a direct line between the source of light and the eye, i.e. the two surfaces of the lens are at right angles to this line. By gradually approaching the lens to the eye a position can be found where the light is focussed on to the surface of the eye or into the substance of the cornea, so lighting up these parts and showing up foreign bodies or abnor malities.
Still using the first lens as a means of illumina tion, one can use a second lens as a magnifying glass, so as to obtain an enlarged image of the illuminated area. The second lens is placed a few inches from the eye in the path of light from the first lens. The surgeon places his eye at the focus of the second or magnifying lens, and by this means minute foreign bodies can be detected and removed.
The Ophthalmoscope.This consists essen tially of a concave mirror- of 20 ems. focal length with a central aperture. The mirror reflects convergent rays from the source of light into the eye to be examined. The light-rays are made more convergent by passing through the refract ive media, especially the lens, of the eye, and so cross in the vitreous humour, and light up the fundus. From every point of this illumin ated surface in the eye rays are reflected back again to the observer's eye which is looking through the aperture in the mirror. Supposing the patient's eye to be em metropic (i.e. neither long sighted nor short - sighted) the rays emerge in a parallel beam, and -if the surgeon's eye be also normal (em metropic) these parallel rays will fall on his retina in focus, so giving a clearly-defined upright image or picture of the fundus of the eye examined.
This is known as the direct method. The lamp (if the examination is held in the dark - room) should be on a level with the eye to be examined, and in such a position as to leave the eye in shadow. Thus in examining the horse's near eye the lamp should be placed a little in front of the horse's head and about a foot to the off-side.
The observer's head has to be brought fairly close to the eye to be examined, from as far as 2 feet away down to 6 inches, depending on tl whether the cornea and lens or the fundus are being examined. The view of the fundus obtained by this method is enlarged, being magnified about 15 diameters in an emmetropic eye. The observer's eye must be at rest, i.e.
not accommodated at all, but as it were looking into the distance, and this is a matter of practice. The placing of a low concave lens behind the aperture in the ophthalmoscope mirror will help a beginner. Atropine will paralyse and prevent accommodation on the part of the patient.
Examination of the horse's eye is more easily and satisfactorily carried out in daylight than in the dark - room. The horse should stand in the stable parallel to an open door or window with the eye to be ex amined in shadow. The observer then re flects the light from the window into the eye with the ophthal moscope. The attend ant should keep the head as steady as possible by means of one hand on the ear, the other holding the bridle. It is advis able to dilate the pupil with atropine or homatropine drops about an hour before the examination is made. The direct method has the ad vantages of the up right image and of a high magnification of the parts examined.
The indirect method allows of a more general view, of much less magnification (4 or 5 diameters), but it is less easy to apply in veterinary practice because of the difficulty of keeping the patient quiet during the observation. In addition to the ophthalmoscope a biconvex lens, usually about 14 D, is also used. It is held at a distance slightly greater than its focal length from the eye to be examined. The rays from the ophthalmoscope are thrown into the eye through the lens. This converges the rays, which cross in the vitreous, illuminate a part of the fundus, and emerge as a parallel pencil of light from a normally-refracting (emmetropic) eye. The rays then pass through the convex lens and are brought to a focus at a point behind it, giving a real inverted image of part of the fundus. This is what the observer sees, and he must accommodate to see this clearly whilst looking at the lens. The procedure is to place the lamp as in the direct method, put the ophthalmoscope to the observer's eye, throw a beam of light into the horse's eye until the pupil is lighted up and the greenish-golden reflex from the fundus appears. Then interpose the lens, holding it between finger and thumb and sup porting it in position with the little finger against the horse's head. A speculum is usually required, and it is necessary to use both cocaine and atropine in order that the animal may not resent the speculum and the bright beam of light. Two assistants will be required, the one to hold the horse's head, the other to hold the lamp.
Opacities in the refractive media of the eye— cornea, lens, or vitreous—can be detected as black specks in the illuminated greenish field, and as the eye is rotated they move, if in cornea or anterior surface of the lens in the same direction as the eye, if posterior to the centre of the lens in the opposite direction to the eye movements. By close observation of the movements, an idea of the depth of the opacity can be obtained.
In the horse the fundus is seen to be brightly illuminated with a surface of greenish-blue and gold called the tapetum lucidum. Below the tapetum and slightly to the temporal side is the round optic disc or papilla—the point of entrance of the optic nerve. This is of a pinkish white colour. Radiating from the papilla are the retinal arteries and veins—showing as a much closer network in the horse than in other animals. Outside the area of the tapetum lucidum is the dark purple or brown area of the fundus, but it is not very easily examined.
In the ox the tapetum is greenish-blue; in the dog golden-green and scintillating. There is no tapetum in the pig. The retinal vessels are fewer and more distinct in the other animals than in the horse, and the arteries and veins can be distinguished.
An ophthalmoscopic examination not only provides information with regard to small opacities in the cornea and lens, but it is the best means of detecting diseased conditions of the vitreous humour, the choroid, retina, and optic nerve. These are uncommon conditions in the domesticated animals, but they will be discussed briefly under the respective headings.
Retinoscopy for Myopia, Hypermetropia, and Astigmatism.One further and important use of the ophthalmoscope is to determine the refractive power of the eye, so detecting myopia, hypermetropia, and astigmatism. This is done by the practice of retinoscopy or the shadow test.
When rays of light from a concave mirror are thrown on to the eye the pupil is illuminated by the reflection of the light from the fundus. If the mirror is then slowly rotated round an axis lying in the plane of the mirror, the beam of light moves either laterally (mirror rotated round its vertical axis) or up and down (mirror rotated round its horizontal axis). By this means the non-illuminated edge or shadow bordering on the bright area is made to move across or up and down the pupil, and, by ob serving the direction of its movement, the refraction of the eye is determined.
Without discussing the theory of retinoscopy, the results may be indicated. Rotating the mirror laterally the shadow may move to the right or to the left, or it may remain stationary. Movement of the shadow in the same direction as the mirror is rotated (i.e. with the mirror) indicates myopia. To determine the degree of myopia, a series of concave lenses of varying strengths in diopters ranging from 5 D to 3 D are required. These are inserted one at a time in a spectacle-frame arranged in front of the horse's eye. Commencing with a low concave glass (say -1D), lenses are tried until on rotat ing the ophthalmoscope mirror the shadow remains stationary. Then the number of the concave lens used plus 1 gives the degree of myopia in diopters or M= (n+ 1)D, where 72 is the number of the concave lens and M is the degree of myopia.
Movement of the shadow in the reverse direc tion to the mirror indicates one of three condi tions, namely, myopia of less than 1 diopter, emmetropia or normal refraction, or hyper metropia. To determine which of these is present and the extent of the abnormality, if any, a series of convex lenses are used. The result is given by the formula 11 = (n - 1)D, where H indicates the degree of hypermetropia and n the number of the convex lens used to secure immobility of the shadow. Thus, if the convex lens is 0.75 D the degree of hyper metropia is - 0.25 diopters—i.e. there is D myopia. If the convex lens used is 1 D, then H = (1-1)D =0, and the eye is emmetropic with normal refraction. If the lens used is D, the hypermetropia is 0.5 D.
If, without using any lens, the shadow remains stationary, the eye is myopic to the extent of 1 diopter, as is seen by using the first formula.
Astigmatism is determined by the same method, the refractive power of the eye being determined for the vertical and horizontal meridians. In examining an eye the refraction may be found normal in one meridian and either myopic or hypermetropic in the other; or the refraction may be abnormal in both meridians, but in different degrees.
The retinoscopic examination is best made in daylight, the horse standing in a stable parallel to a window or open door with the eye M shadow. Atropine or homatropine should be used an hour 1: efore the examination begins.
The observer stands about one yard or a little further away from the horse's eye. The correct ing lenses, instead of being fixed in a spectacle frame, may be held in front of the horse's eye by an attendant. Another attendant keeps the head steady by holding one ear and also the bridle.
The investigations of different authors as to the common refractive errors in horses give somewhat divergent results. Nicolas in France found the majority of horses slightly hyper metropic. Fred Smith, on the other hand, states that the great majority of horses are slightly myopic. All are agreed that the majority of horses are astigmatic, with the horizontal meridian the less curved and so the less refractile. A slight degree of astigmatism in this direction may be said to be physiological in the horse.
Myopia or hypermetropia of anything over 1 diopter is serious in that it causes blurred vision, and is commonly held to be associated with shying.
Lang and Barrett,i in an investigation on the"Refractive Character of the Eyes of Mammalia,"found the cow to be commonly hypermetropic and often astigmatic; dogs and cats to be practically emmetropic; and most wild animals to be hypermetropic.
Myopia, or short-sightedness, is the condition in which the rays of light entering the eye are brought to a focus not on the retina but in front of it. It is most commonly due to an excessive length of the eyeball from front to back, although other causes, such as excessive curvature of the cornea or of the lens, may be responsible for the condition. The myopia can be corrected by placing a suitable concave lens in front of the eye.
Hypermetropia, or long sight, is the condition in which the rays of light entering the eye are brought to a focus behind the retina. It most commonly due to shortness of the eyeball from front to back, but may be due to flatten ing of the cornea or to absence of the lens due to dislocation or after cataract extraction. It can be corrected by placing a suitable convex lens in front of the eye.
Astigmatism is that condition in which the refracting surfaces of the eye (cornea and lens) are not spherical but are curved irregularly. As a result, the rays of light passing through one meridian of the eye are not brought to a focus at the same point as those passing in through another meridian. The cause is usually due to uneven curvature of the cornea, and in"regular"astigmatism the directions of greatest and least curvature are at right angles to one another and lie in the vertical and horizontal meridians respectively. This is the common condition in the horse, and it is a congenital one.
Catoptric Test. This is a test which is some times used for the detection of opaque specks in the cornea or lens. If a taper or candle is held in front of the eye there will be seen three images of the flame on looking into the eye. These are formed on the catoptric (or reflecting) surfaces of the eye,, namely, the surface of the cornea, the anterior surface of the lens, and the posterior surface of the lens. The first and second images are upright, the one from the cornea being the larger and more distinct. The third image is the smallest and is inverted. When the light is moved the first and second images move in the same direction as the light, but the third inverted image moves in the opposite direction. If the reflecting surfaces are normal, and the media (cornea, aqueous humour, and lens substance) clear, the images are sharp and distinct. Opacities intercept the rays of light and prevent any reflection, so that in case of a diffuse cataract no third image will be visible, and if the anterior capsule of the lens is thickened and opaque the second image may be more or less blurred. Specks in the cornea or lens interfere with the momentary images as the light passes across. The test is useful in some cases, but ability to use the ophthalmoscope provides a method giving more information and of greater re liability.
Anaesthesia for Eye Operations Anesthesia of the Lids. Where operative pro cedure is to be limited to the lids, in the majority of cases it will be found that local anaesthesia is all that is necessary; and, provided that care is used in the method, little or no restraint will be needed. A few drops of a 5 per cent solu tion of cocaine hydrochloride with adrenalin 1 in 2000 should be instilled into the subcon junctival sac every couple of minutes for a quarter of an hour. This will give satisfactory anaesthesia, though somewhat limited in extent, in the lids themselves. In case it may be found necessary to extend the field after the operation has been commenced, it is usually best to strengthen the conjunctival anaesthesia by a subconjunctival injection near the canthi of the lids and an intradermal or hypodermic in jection on the skin surface of the lids, using a 1 per cent solution in both cases, keeping in mind that for the upper lid the sensory nerves are derived from the ophthalmic, and for the lower lid from the maxillary, division of the fifth cranial nerve.
In dogs, if not otherwise contra-indicated, such anaesthesia of -the lids may be preceded by an injection of morphine half an hour before operation.
Anaesthesia of the Globe. In all operations on the globe, on the other hand, owing to the in ability to obtain co-operation on the part of the patient, general anaesthesia is usually pre ferable on account of the danger of movement and to allow of more careful manipulation and finer work. In the human subject the whole globe of the eye can be anaesthetized by means of local applications for most of the surgical procedures, and the same methods can be adapted for use in animals for such interference as examination, and removal of foreign bodies. Of local anaesthetics, cocaine hydrochloride is the best drug, and though more toxic generally has not the same irritating action on the con junctiva, and is more reliable than novocaine. The 5 per cent solution, together with adrenalin 1 in 2000, is a useful strength for instillation into the conjunctival sac, the drops being applied by soaking a small piece of cotton-wool in the solution and expressing the drops required into the exposed conjunctiva.
This should be done every few minutes for a quarter of an hour, when the eye will be found to be anaesthetized. Atropin 1 per cent can be added if it is desired to dilate the pupil at the same time. Many workers, in addition, supplement this by a subconjunctival injection near the globe of a 1 per cent cocaine solution. It may be necessary if the condition demands interference with the external eye structures, and possibly prolongs the period of anaesthesia.
In dogs the use of strong solution of cocaine, such as the 10 per cent, is not recommended for instillation as toxic effects from absorption may result. The symptoms are salivation, increased respiratory movements, excitement and hyperamthesia, and clonic spasms. The amount injected into the tissues should be regulated not to exceed one grain for a dog of the fox-terrier size.' Some dogs appear to show a special idiosyncrasy in respect of this drug.
Of the substitutes for cocaine, those most commonly used are novocain, fl-eucaine, and holocaine. Novocaine may be used in 2 to 5 per cent solution in water; fi-eucaine and holo caine similarly. All three are soluble in water, and the solutions may be sterilized by boiling.
General anesthesia is induced in the larger animals by the use of chloroform; in the dog with chloroform, A.C.E. mixture, or ether—in each case with the usual precautions.
II. Diseases of the Eyelids The skin of the eyelids is subject to various skin diseases similar to those on other parts of the body and requiring similar methods of treatment. Some of these conditions are of importance to the ophthalmic surgeon because any irritation set up by disease of the lids may extend to the conjunctiva or to the eye itself, or may cause rubbing and scratching on the part of the patient, with consequent damage to the eye.
Parasitic skin diseases, such as mange in the dog and cat, and ringworm in the calf and less often the foal, affect the skin of the eyelids.
Eczema of the eyelids may be part of a general eczema about the head, or it may be an irritation of the skin due to discharge from the conjunctiva, or due to a flow of tears over the lid margin (epiphora), or to the frequent use of some eye lotion, especially atropine (Fig. 174).
Treatment. The parasitic affections must be treated in accordance with their own special requirements, always remembering that any untreated irritation of the lids is likely to lead to damage to or infection of the eye by reason of the rubbing or scratching caused. Eczema will also require to be treated on general lines, but if due to epiphora or conjunctival discharge a little vaseline or zinc ointment smeared on the lids will protect the skin. If there is irrita tion, an ointment of sulphur, oil of tar, and lard will often relieve the condition, whilst painting with orthoform in glycerine or in collodion (1 in 16) will anaesthetize the part for several hours.
Blepharitis. Blepharitis is the name given to an inflammatory condition of the lid margins, which may be differentiated into two forms according to degree, namely, superficial and deep or ulcerative. The condition is really an eczema of the parts.
It may appear in dogs and cats from irrita tion resulting from parasitic infection, or much more commonly from the irritation of some purulent discharge from the conjunctiva, especi ally in distemper.
In the ulcerative form the condition tends to be more severe, with destruction of the lash follicles by follicular suppuration. In both forms there is a gumming of the lids and matting of the lashes.
Treatment consists in the application of ointments to the lid margins, a useful one being the ung. hydrag. flay. (10 grs. to 1 oz.), together with antiseptic eye-washes for the relief of any conjunctivitis present. The scabs and crusts should be removed by softening first with olive oil and then bathing with boracic acid lotion. The conjunctiva and cornea must both be watched for any signs of infection or ulceration.
Hordeolum, commonly called"Stye,"is a localized suppuration in the follicle of an eye lash. It is a rather painful condition and leads to some cedema and general inflammatory swelling of the lid in its neighbourhood. Very often there is a succession of styes.
Treatment. — The process may often be aborted by plucking out the affected hairs. As the small abscesses form they should be evacuated.
Chalazion, or tarsal cyst, may be a retention cyst or possibly a granulomatous condition of a Meibomian gland. It appears as a tumour, from the size of a barley-grain to a hazel-nut, in the thickness of the lid, hard and painless, the conjunctival surface over it looking rather pale from pressure. The contents are pasty and viscid.
Treatment. The tumour can only be got rid of by operation. It is best evacuated by an incision from the conjunctival surface after anaesthetization of the part. After opening the sac its wall is scraped with a small curette and the conjunctival sac washed out with boracic acid lotion.
cEdema of the Lids.(Edema of the lids may be due to some systemic disturbance, as acute kidney condition, or may be part of the symptoms in the final stages of cardiac failure, though in animals it is not common to find these processes in operation.
In the horse it is much more often seen in association with general or local septic condi tions, and it may be present bilaterally as part of the cedema of the face in purpura haamo rrhagica, in influenza, or in the marked cedema which follows the intense inflammatory swelling of some retropharyngeal infection. In the uni lateral form it is generally the result of some local septic condition of the lids or conjunctiva or globe, often following a wound.
When limited to one eyelid it is usually the upper lid that is affected, and it may give rise to the impression that some proptosis is also present.
In some districts the attacks of biting flies produce a similar swelling.
Treatment consists, apart from the measures directed to the relief of any general or local septic condition, in the application of hot-packs and antiseptic eye-washes. In cases of pharyn geal swelling, where the cedema is intense with exposure of the conjunctiva and ulceration, puncturing the lids and insertion of drainage silk may give relief. As a protection from flies, leather fringes may be worn while the animal is working.
Ankyloblepharon is a condition following blepharitis, or burns or other injuries, in which the margins of the upper and lower lids become either partially or completely united as a result of healing of the opposing raw surfaces.
Symblepharon, or union of the bulbar con junctiva with that of the lids, may occur at the same time. Here also burns, injuries, and ulcers are the usual causes. The treatment is operative and consists in dividing the united parts, and then preventing reunion by inter posing flaps of healthy conjunctiva on the raw surfaces.' Lagophthalmos, or inability to close the eye, may be due to paralysis of the orbicularis oculi muscle following injury to a portion or trunk of the seventh cranial nerve, or, on the other hand, it may be due to an inability of the eyelids to approximate owing to tumour within the orbit or excessive granulation process following trauma of the globe.
The danger to the eye lies in the exposure of the cornea, with drying of its surface and absence of the clearing action of the lids, this soon producing a keratitis and ulceration. In paralytic cases there is usually present some amount of movement in the globe itself due to the action of the eye muscles, which reduces the severity of the exposure and accounts for the small amount of damage to the cornea in some of these cases.
In cases where the lagophthalmos is due to the presence of tumour, removal of the latter, especially those on the membrane, will remedy the condition, and it is common experience that a markedly opaque ulcerated cornea clears up rapidly once the tumour is removed if the damage to the cornea is not of long standing.
In paralytic cases the cornea should be pro tected by suturing the lids together, the stitches going no deeper than the skin. Strapping with adhesive plaster gives similar protection and has the advantage of allowing regular inspection as to the state of the cornea.
This protection should be afforded until the restoration of the nerve function is observed by movements of the lids. Where the condition is due to a staphyloma it should be treated accordingly.
In many cases of bilateral seventh nerve injury, such as occurs when a horse strikes the occiput on the roof of a truck or door, though the muscles of the nose and mouth are paralysed the fibres to the orbicularis oculi escape injury.
Ptosis.Ptosis, or inability to raise the upper lid, is usually an acquired disease in animals, and even then is rare. The drooping of the lid is due to a paralysis of the levator muscle supplied by the third cranial nerve, or to a temporary injury to the lid itself producing cedema and immobility.
In injuries, the ptosis disappears with the improvement in the state of the lid, while in persistent paralysed conditions it may be necessary to split the lid and join the tendon of the affected muscle either to the fibres of the frontalis or to those of the superior rectus.
Trichiasis, or turning-in of the eyelashes, may be present as a complication of entropon but may occur apart from the latter condition. Trichiasis is brought about by chronic con junctivitis causing distortion of the eyelid, or by chronic blepharitis. It sooner or later leads to a keratitis through irritation of the cornea, with pain, lachrymation, opacity, and possibly ulceration.
Very often only a group of lashes growing close together in a distorted fashion may be inverted instead of the whole row.
Treatment. Plucking out the lashes will give temporary relief, but it is usually more satis factory to remove the follicles of the offending hairs. Two parallel incisions are made along the margin of the lid, one on each side of the ciliary row to the extent of the inverted lashes. The incisions are continued to a sufficient depth to ensure the complete removal of the follicles.
When the whole row of lashes is affected, the removal of an elliptical piece of skin from the affected lid, as recommended in cases of entropion, may give a satisfactory result.
Entropion, or turning - in of the eyelid, may affect one or both eyes simultaneously. Trichiasis is also usually present. The effect on the cornea is always serious, and is due to the irritation of the lashes and rough edges of the lids. A keratitis results, with possibly corneal ulcer, which may go on to staphyloma or rupture of the anterior chamber. A con junctivitis is always present and soon glues the lids with a purulent discharge.
The condition may be congenital or acquired, the former condition being often seen in puppies, in which case it may affect all the puppies of a litter. The bilateral form is commonest in dogs, and when acquired seems to be preceded by a catarrhal conjunctivitis of low grade, the chronic thickening and contraction of the con junctiva shortening the palpebral aperture and inverting the lids. As a senile change it is not common in animals.
In dogs there is certainly some evidence of a tendency for the disease to run in families, and there is also a well-marked predisposition in some breeds, particularly Pomeranians, Chows, and Poodles, to the complaint.
Once the lids are inverted by structural change operation is necessary and should be done as soon as possible to relieve the irritation on the cornea. At the same time it must be remembered that spasm of the orbicularis muscle (blepharospasm) due to any irritation in the conjunctiva causes a turning-in of the lids which simulates structural entropion. Treat ment of the conjunctivitis and removal of the irritation relieve the spasm without operation.
A preliminary treatment for clearing up the infection should be carried out for a few days prior to any operative interference, the con junctival sac being irrigated twice daily with a solution of perchloride of mercury 1 in 10,000, and the lids being dressed with ung. hydrag. flay. 2 per cent, after any long hair has been removed.
Treatment. For the condition in young dogs and in the congenital form where shortness of the palpebral tissue is marked, the operation of canthotomy or canthoplasty appears to give excellent results.
Canthotomy consists in simply enlarging the palpebral aperture at the external canthus. A pair of straight blunt-pointed scissors are intro duced at the outer commissure and the skin and conjunctiva divided to the required distance, the length of the skin incision being a little greater than that in the conjunctiva.
In canthoplasty the operation consists of, in addition to the incision described, a suturing of the severed conjunctiva to the skin in order to ensure union of mucous membrane to skin and not to bulbar conjunctiva. The suture in the angle of the newly-formed canthus should be put in first, and after that as many stitches as are required may be inserted in upper and lower lid margins.
In other forms of entropion, where the inver sion is not due simply to narrowness of the fissure, there is a choice of a number of opera tions for everting the inturned lids.
The simplest method, and one which is almost uniformly effective in the dog, consists in the removal of an elliptical piece of skin from the affected lid, the long axis of the ellipse being parallel to the lid margin. This may be done by catching up a piece of skin in forceps and removing the desired amount with a pair of slightly-curved scissors. The size of the open ing thus made will have to be regulated by the amount necessary to retract the eyelid when the edges of the wound are brought together by sutures.
As a preliminary, the hair is removed from the skin of the lid with scissors and the skin is painted with tincture of iodine. Local anaes thesia is induced by means of cocaine and adrenalin injection. The piece removed may include a strip of the orbicularis muscle, but the conjunctiva lining the lid must not be included. After suturing, the wound may be painted with iodoform and collodion as a pro tective dressing.
It is usually necessary to treat both lids, and one may also find it of advantage to com bine this method with canthotomy or cantho plasty.
For animals the above procedure appears to be all that is necessary, but in the human subject the procedures are directed more to wards the alteration in shape of the tarsal cartilage or in the position of the cilia.
Ectropion.This is a condition in which the eyelid is everted, the conjunctiva being exposed. Though in some breeds of dogs, notably blood hounds and St. Bernards, the condition is normally present to a mild degree, as a patho logical condition it is not common. When seen the condition is almost always confined to the lower lid, and is usually classified according to its etiology into muscular, cicatricial, or paralytic.
The muscular type is a senile change not seen in animals. The cicatricial variety is the form usually met with, and it arises from in correct apposition of the edges in the healing of a wound or tear of the eyelid. There is often an epiphora with scalding of the face from the overflow of tears.
Treatment consists of operative measures directed towards tightening up or elevating the drooping lower lid.
If due to cicatricial deformity, the scar may be excised and the skin of the lids thus shortened may be brought into correct apposition and sutured, the conjunctiva being treated in a similar manner. Another method, which gives good results when the skin of the lower lid is too long, is to excise a triangular piece of the whole thickness of the eyelid. This V-shaped piece has its base at the lid margin, and it is well to remove a wider area of the conjunctiva and tarsus than of the skin. The edges of the conjunctival wound are united with three or four sutures put in very securely to avoid a premature giving way. The frequent use of a little boracic ointment inside the lid lessens the irritation of the eyeball by the sutures. The skin wound, including the orbicularis, is also closely sutured, and a collodion dressing applied.
Wounds and Injuries. Tears of the lids are the commonest form of injury, the lower lid being the more frequently involved. In the horse, catching the lid on a hook or nail in the stall or on barbed wire in a fence are common causes. More rarely parts of the harneis or winkers may be the offending objects. In dogs, bites and scratches are frequently to blame. More extensive injuries to the lids, either one or both, may be caused by a kick over the orbit, with fracture of some part of the bony processes and serious contusion of the soft parts. Marked oedema of the lids may be present simulating proptosis, and there may be injury to the globe of the eye itself.
Treatment of the lid injuries themselves will depend to a great extent upon the degree and position of the lesion. Injuries confined to either the skin or conjunctiva of the lids may be sutured with confidence, the material being preferably fine silk for the conjunctiva and fine silkworm-gut for the skin. On the other hand, tears involving the whole thickness of the lids, especially when across the fibres of the orbicu laris oculi, seldom give satisfaction when sutured, the continual strain of movement causing the sutures to cut out in a great number of cases. The lower lid, however, is the more amenable to treatment by suture on account of its lesser mobility, and, for the same reason, plastic operations for the repair by means of a flap of skin of some defect due to destruction of the lid by injury, or after operative removal for malignant growth, are much more hopeful in the lower than in the upper lid.
Because of the frequent dragging out of ordinary sutures, pin sutures are often recom mended for wounds of the eyelids in the horse. The pins are inserted about half an inch apart, taking a fairly deep hold of the skin edges. A piece of fine silk is then wound in a figure of eight pattern round each pin, or continuously from one pin to the next in series, and tied. The points of the pins are then cut off with pliers. These sutures give considerable sup port to the wound edges and lessen the mobility of the part, so favouring union.
After this or any other operation on the eye lids in the horse it is unwise to allow the animal to be loose in a box or to be tied in a stall in the ordinary way. The horse should be put on pillar-reins of such a length that he is unable to rub the wound.
As the result of injury to the lower lid it occasionally happens that epiphora results, the lachrymal discharge escaping through the rent. In these cases it will often be found expedient to dissect the conjunctiva from the lid on each side of the tear and suture this layer separately with fine silk, and to bring up a flap of skin from the face to fill the gap in the lid. In other cases where there is a simple rent without loss of tissue suturing may be successful if a small drainage-tube is inserted at the bottom of the wound to carry away the tears and thus prevent maceration of the edges until healing of the upper part of the wound has taken place.
Not infrequently a large part of the lower lid may be removed without much remaining deformity, and though tightening of the lid may result, with shortening of the palpebral aperture, a very serviceable eye remains.
Tumours involving the Lids. — The nasal portion of the lower lid and the nasal canthus are the external parts most early involved in the extension of an epithelionaa, of the mem brana, and these parts if infiltrated should be freely excised when the membrana is removed. It must be remembered that the dangerous spot is that point where the fibres of the orbicu laris are inserted to the lachrymal tubercle, and the neighbourhood of the ducts, for when recurrence takes place after operation it is usually at this site.
The removal of the puncta and ducts in the operation causes some overflow of tears, but in most cases the discharge soon ceases either due to the restoration of the continuity of the ducts or to loss of the aspirating effect of the lachrymal sac.
The effect on the lower lid of such an operation is usually one of decreased mobility, with reduc tion in size of the palpebral aperture, but the function of the eye is usually in no way im paired.
A granulomatous condition of the caruncle, membrana, and lower lid due to the presence of parasitic embryos of the Habronema species may be easily mistaken for tumour growth, but should be distinguished from it by the presence of small necrotic areas about the size of a pin's head, within or immediately below the mucous layer of the surrounding conjunctiva.' III. Diseases of the Membrana Nietitans third eyelid serves as an extra protection for the globe of the eye, and by its sharp"flicking"movement across the eye it removes any foreign particles from the front of the globe. It consists of a semi-lunar plate of hyaline cartilage covered on its free anterior and posterior surfaces with conjunctiva. There are numerous nodules of lymphoid tissue in the membrana, and on its deep face are the openings of a small gland, the Harderian gland, something like the lachry mal gland in structure which secretes a lubricat ing fluid. When the retractor muscle of the eyeball contracts, the membrana is protruded and shoots across the eye, clearing its surface.
The membrana is subject to various diseased conditions in the different animals. The con junctival covering is frequently involved in conjunctivitis (q.v.), especially of the follicular type. Various tumours, notably papilloma and, more common and more serious, epithe lioma, frequently originate from the epithelium covering the membrana, especially in horses and cattle Whenever the membrana is found to be the point of origin of a tumour the whole structure should be amputated without loss of time.
Cyst of the Membrana.Sometimes there is in the dog or cat a small swelling in the sub stance of the membrana, which is smooth and covered with conjunctiva, firm, painless, and only objectionable because of its conspicuous position as it protrudes at the inner canthus.
The nodule is the result of obstruction or hyper trophy of the Harderian gland and the condition is often bilateral (Fig. 175). Because of its un sightliness, the best treatment is to snip off the portion of the membrana in which the nodule occurs with scissors.
Paralysis of the membrana occurs commonly in the dog and cat as the result of some debilitat ing disease, especially distemper. The animal is brought for treatment because of a"film over the eyes,"for both are usually affected, and it is found that the two membranes are protruded half - way or more across the eye. Usually the animal looks anomie and is in a weak state, and the history of a recent attack of distemper is common.
Treatment. With improvement in the general health the condition generally rights itself. The prescribing of tonics, such as arsenic, strychnine, or iron, and advice as to food, exercise, and general management form the proper course to adopt. The client should be informed that the condition often takes weeks or months to return to normal, but that it will eventually do so. Not infrequently such a prognosis is unpalatable to the owner. A cure is desired at once. In such cases amputation of the offending membrana may be practised without any noticeable harm to the eye. Some times indeed the operation has to be advised by the surgeon because the membrana is so far protruded as to interfere with sight and seriously to affect the cornea. To amputate the membrana it is only necessary to seize it with fixation forceps, draw it well forward, and excise it with a strong and sharp pair of curved scissors.
IV. Diseases of the Lachrymal Apparatus The lachrymal apparatus comprises (1) the lachrymal gland, situated within the orbit beneath the supra-orbital process. It secretes the clear lachrymal fluid or tears. (2) The excretory ducts of the gland opening into the dorso-lateral part of the conjunctival sac near the superior con junctival fornix. (3) The puncta lachrymalia, the entrance to the lachrymal ducts, one on each lid near the internal canthus. They are fine, slit-like openings in the horse, and pin-hole in shape in the dog. The puncta are normally in contact with the globe at the conjunctival reflec tion and occupy positions above and below the lams lachrymalis respectively. From the point of view of drainage the lower punctum is the more important, as most of the lachrymal fluid leaves by this route. (4) The lachrymal ducts or canaliculi, two in number, extend from each punctum to the lachrymal sac, either entering separately or, as is more common, fusing after convergence before entry. The ducts are lined by stratified epithelium. (5) The lachrymal sac is the dilated origin of the naso-lachrymal duct, and occupies the funnel-shaped portion of the lachrymal bone known as the fossa of the lachrymal sac. It is continued by (6) the naso lachrymal duct, which makes its exit along a bony canal through the outer wall of the sinuses and nasal cavity. The naso-lachrymal duct opens on the floor of the nostril in the horse, near the junction of the skin with the nasal mucous membrane, by an oval opening which can be seen on inspection of the nostril. In the horse the upper part of the duct is about 8 mm. in diameter, at about its middle the diameter is reduced to 3 or 4 mm. and then widens near its terminations. Valve-like folds of mucous membrane are often present which, together with the construction at the isthmus, tend to make the passing of a probe a matter of difficulty. In the dog the naso-lachrymal duct usually opens on the lateral wall of the nostril below the inferior turbinal.
The functions of the lachrymal apparatus may be interfered with as the result of injuries to the orbit or bones of the face, or of such injuries of the skull as involve nerves supplying the ocular structures. The lachrymal gland may be injured in fracture of the supra-orbital process of the frontal bone or may be involved in consequent sepsis if the fracture is compound.
Otherwise the lachrymal gland is practically never diseased. Excessive or continuous lachry mation is often seen, and should lead to a careful inspection of the cornea or conjunctiva for the presence of a foreign body.
Epiphora, literally a flow of tears, is the name given to an overflow of tears which, unable to escape in the ordinary way, come over the lid margin and trickle down the face. The con tinuous flow of tears over the skin soon causes it to become bare and eventually inflamed and even ulcerated. Epiphora is the commonest sign of abnormality in some part of the lachrymal apparatus, puncta, canaliculi, sac, or nasal duct. Apart from the unsightly appearance and the scalding of the skin of the face, epiphora merits attention because the underlying cause is often some disease with more important effects on other structures. Moreover, lachrymation is usually excessive. Malposition of one or other punctum, usually the lower one, is a common cause of epiphora. This may often be brought about by inversion (entropion) or eversion (ectropion) of the eyelids. In some lases there is stenosis or even occlusion of the punctum as the result of catarrhal conjunctivitis or blepharitis, or because of tumour of the caruncle or due to the presence of a foreign body. Congenital atresia of the puncta has been recorded in the foal.
Fracture of the bony orbit involving the sinuses usually presents a line of cleavage through the fossa of the lachrymal sac with injury to the latter structure, producing a tem porary or permanent obstruction.
Treatment. With the repair of entropion or ectropion the overflow of tears may cease. Where injury to the lids has been followed by healing in which the lower punctum is not replaced in its normal position on the globe, and epiphora has resulted, a plastic operation such as one of those recommended for entropion can be adopted.
In a large number of cases following injury complete restoration of continuity of the passage occurs, provided that no infection of the ducts persists after healing of the surrounding parts is completed.
Treatment in traumatic cases is usually in the direction of reduction of the deformity of damaged bones and removal of any fragments. Sepsis, of course, is treated on general lines. Stenosis of the puncta or canaliculi is treated by slitting open the lower punctum and canal by means of a special probe-pointed knife Weber's knife. The probe point is inserted through the punctum into the canal and then the cutting edge is turned so that in cutting out the blade will open up the canal and make a slit on the lid margin inclined towards the eye, so that tears readily gravitate into it or are aspirated into it by the eye movements. The wound edges must be kept open by means of a probe for a few days, after which they show no tendency to unite.
The caruncle may be swollen as the result of chronic inflammation in adjacent structures, it may become hypertrophied, or it may be the starting-point of a tumour. Benign tumours sometimes _affect the caruncle, but more com monly it is the site of sarcoma or epithelioma. An enlarged caruncle often obstructs the ducts.
Treatment. For a chronic swelling or hyper trophy of the carunclo it is best to snip off the whole structure with scissors or apply a liga ture so that it will slough in a few days. If malignant disease is suspected then early re moval of the growth is the only remedy. Neigh bouring structures are involved early as a rule, and a serious operation is usually necessary in order to remove all traces of the infiltrating growth.
Daeryo-cystitis, or inflammation of the lach rymal sac, is a rare condition in animals. It may be caused by chronic catarrh of the lachrymo-nasal duct or structure of the duct with consequent distension of the lachrymal sac. The retained secretion favours infection, and so usually a chronic dacryo-cystitis is set up. Sometimes pyogenic organisms gain an entrance and acute dacryo-cystitis with abscess formation occurs. Sometimes the lachrymal sac is involved in an injury to the bone by means of a blow. If there is a wound the sac may be opened and a lachrymal fistula opening on to the face may remain when the rest is healed. Following this infection of the sac may easily occur.
Symptoms. There is a swelling which may or may not be painful, just internal to the inner canthus. Pressure over this may cause the sac contents, a catarrhal exudate or actual pus, to escape from the puncta into the conjunctiva. With suppuration the swelling may point and open near the inner canthus. Epiphora is present because of the obstruction.
Treatment. The best procedure is to extir pate the sac completely, if possible without opening it. An incision is made in the skin over the swelling, and the sac thus exposed is carefully dissected from its attachments and removed. If the sac is opened during removal, or in the case of an inflamed sac with a fistula, or one in which an abscess has formed and been evacuated, the walls should be curetted, and then disinfected with some reliable agent such as tincture of iodine or strong silver nitrate solution. Sometimes the attempt is made to produce a fistula from the sac through the lachrymal bone into the nose, and this, by reason of efficient drainage, usually brings about an improvement.
After extirpation of the lachrymal sac for any reason the flow of tears over the face is not very serious, providing that the inflamma tory conditions in the adjacent structures are cured at the same time.
Obstruction of the Nasal Duct.This is one of the commonest causes of epiphora. The closure of the duct may only be temporary as a result of nasal or conjunctival catarrh, or a permanent occlusion may occur from the same cause. The temporary obstruction is sometimes made permanent by rough and too frequent use of the probe. Another cause of obstruction is a malignant growth of the caruncle or other parts in the neighbourhood, with extension to the lachrymal sac or the bone. With the removal of a tumour, the parts may be so damaged that scar tissue obstructs the duct, and the same happens when the lachrymal sac is extirpated. The one constant sign is epiphora.
Treatment. When the duct has been cut across or destroyed at its origin by some opera tion the condition is irremediable. A tem porary obstruction due to catarrh is best treated in the horse by means of frequent injections of normal saline solution through the lower opening of the duct in the nostril. In the dog this cannot be done, since the nasal orifice is out of sight. In this case a fme bougie or silver-wire probe must be passed from above, if necessary, after slitting up the lower canaliculis. If this is impossible, and the epiphora troublesome, a fistula must be made through the lachrymal bone into the nose.
Tumours originating in the structures of the lachrymal apparatus are rare. Adenomata and malignant growths of the lachrymal gland have been recorded, but the treatment calls for no special mention here apart from the fact that the whole of the lachrymal gland can be removed without fear of exposing the eye to any serious harm.
In nearly all other cases tumours are due to a direct extension of malignant growths of neighbouring parts.' In removal of the globe in cases of epithe lioma one should be careful to see that the lachrymal gland is removed, as well as the soft structures at the medial canthus, for when recurrence takes place after removal of a tumour it will be found in nearly all cases to be in the vicinity of the lachrymal sac.
V. Diseases of the Conjunctiva The conjunctiva is the membrane which lines the inside of the eyelids (palpebral portion), covers both free surfaces of the membrana nictitans or third eyelid, and spreads over on to the globe of the eye (bulbar portion). The deepest part of the conjunctival sac, where the palpebral conjunctiva is reflected on to the bulbar portion, is known as the sulcus, or the upper, and lower, fornix. Close to the free margin of the eyelids the membrane is bound tightly down to the underlying dense fibrous layer of the eyelid known as the tarsus. Here the epithelium consists of a double layer of cuboidal cells. Behind the tarsus the epi thelium is thicker and more loosely held so as to allow greater freedom of movement. The underlying tissue is very vascular and consists of loose lymphadenoid tissue. The epithelium of the bulbar conjunctiva is still thicker and of . the pavement variety, being bound down to the sclera by means of a thin layer of elastic tissue. At the margin of the cornea the conjunctiva slightly overlaps the cornea, this rim being known as the limbus. Here the conjunctival epithelium becomes similar to, and merges with, that of the cornea, having a deep layer of columnar cells, middle layer of cuboidal, and surface layer of flattened cells more or less horny. The blood supply of the conjunctiva is twofold, the posterior conjunctival vessels being derived from the palpebral branches of the ophthalmic artery, whilst in the region of the limbus are very fine twigs passing back from the anterior ciliary vessels. In most cases of conjunctivitis the former alone are congested, whereas ciliary congestion is a characteristic feature of inflammatory conditions of the iris and cornea.
Conjunctivitis. Inflammation of the Con junctiva. This is one of the commonest affec tions of the eye in all animals. It may be caused by any injury to the part, including infection by bacteria, and even where bacterial infection does not initiate the process it is extremely likely to follow and aggravate any injury. On the normal conjunctiva a consider able variety of micro-organisms may be found in small numbers, and with any damage to the epithelium, whether by trauma, dust, infection by flies, chemical agents, or other means, there is exudation from the membrane which pre disposes to the multiplication of the bacteria. The bacteria invading the conjunctiva may be, and usually are, non-pathogenic, as is the case with many air-borne organisms to be found on the normal conjunctiva. They may, however, be pathogenic, and of these some can attack the uninjured and unbroken membrane, as, for example, the gonococcus in man, whilst others only attack the abraded or injured membrane, for example, the tubercle bacillus and staphylo coccus.
Clinically, conjunctivitis shows a variety of types, such as catarrhal, purulent, croupous, follicular, and others, but these cannot be corre lated with specific bacteria, for different organ isms may produce the same type of case, whilst the same organism may be present in quite different clinical types. Conjunctivitis evidenced by marked congestion and more or less discharge, often muco-purulent, is a common accompani ment of many acute infective diseases, such as catarrhal fever and influenza of the horse, malig nant catarrh, and rinderpest of cattle, sheep pox, and distemper of the dog. In all these and similar cases the conjunctivitis is simply a complication of a general disease in which catarrh of mucous membranes is a marked feature. The conjunctivitis is, as a rule, over shadowed by the general symptoms of the disease, but it may be serious, resulting in per manent defects in the eye. Especially is this so in cases of distemper in the dog and cat. Injec tion of the conjunctiva and lachrymation are early symptoms, but a muco-purulent discharge soon makes its appearance, and if the condition is neglected the cornea soon becomes implicated. Opacity of the cornea occurs in many cases; not infrequently ulceration and staphyloma follow, so that any neglect is likely to be attended with disastrous consequences. The treatment follows the lines to be advised for purulent conjunctivitis, but constitutional treat ment, especially during convalescence from the underlying general disease, is also called for.
Whatever the original irritant, with the accumulation of the products of inflammation, bacteria of various kinds, air-borne, and im pinging on the conjunctiva, find suitable con ditions and multiply. They may or may not be pathogenic, but often the ordinary pyogenic staphylococci and streptococci are among them. Out in the open there is little opportunity for bacterial infection to spread from eye to eye, and from one animal to another, but in animals stabled, groomed, frequently handled, and wearing halters or bridles, there is great chance of spread of infection. Even at pasture en zootics of conjunctivitis do sometimes occur in herbivora.
Symptoms. The first sign of conjunctivitis is often simply a flow of tears over the eyelid and down the face of the animal. The eyelids are partially closed and the animal may try to avoid light, though this is not a marked feature in a simple case. On closer inspection the conjunc tiva is much congested, bright red in colour, especially in the depth of the sac towards the fornix, and angry-looking as compared with the normal pale rose-pink colour. This redness, indi cating hyperaemia, may be widespread over the whole membrane, or more or less localized to the seat of injury or to a particular part of the membrane. Thus the tarsal conjunctiva may be especially affected, or the bulbar, or the palpe bral, with special characters in each case. The eyelids themselves often appear swollen or puffy, and they may be distinctly hot. Sometimes the conjunctiva may be swollen, by reason of its infiltration with inflammatory exudate in the subepithelial tissue, and if this swelling is considerable, so as to produce a protrusion of the membrane between the lids, the condi tion is known as chemosis. In addition to an excessive flow of tears there is a secretion or exudation from the inflamed membrane, con sisting of serum and mucus, and in it are shed epithelial cells, leucocytes, and bacteria. Thus even in a slight case there is some discharge, usually sticky in character, so accounting for the dried discharge on the edges of the lids.
Enzatic Conjunctivitis. In herbivora, espe cially cattle and sheep, an infectious or enzootic conjunctivitis may be seen affecting large numbers of animals in a herd or flock. This contagious conjunctivitis has been attributed to a variety of causes, such as irritant pollen or dust from some special soils. It occurs most commonly in summer, spreads rapidly, and is of the purulent type. There is generally some fever, and the cornea often becomes implicated, so that opacity and ulceration are often seen and blindness results in many cases. Several epidemics have been recorded in which the out break followed the introduction into a herd of one animal suffering from purulent conjunctivitis (Law), and recovery from one attack has been noticed to confer an apparent immunity (Trom bower). Thus the evidence is strongly in favour of a specific bacterial infection as the essential cause. In the human subject cases have been recorded"undoubtedly caused by the hay bacillus (B. subtilis). In all of them particles of earth had found their way into the Such an occurrence would provide an easy method of infection in herbivora. In the horse, epidemics of purulent conjunctivitis are also recorded in which the purulent discharge was definitely infective when inoculated into healthy eyes.
Lesions. In a simple case the structural changes in the conjunctiva consist of dilatation of the blood-vessels and increased vascularity, and an infiltration with inflammatory exudate and with leucocytes in the lymph-adenoid tissue. The epithelial cells proliferate and the surface cells are desquamated, so adding to the discharge.
The conjunctiva lining the tarsal plates may be particularly affected, and in this case, where normally the epithelium is tightly bound down to the tarsus, prolonged inflammation causes a folding or ridging of the membrane with marked leucocytic infiltration in the subepithelial areolar tissue. The epithelium itself may also be con siderably thickened. The condition is known as papillary conjunctivitis. In chronic cases the granulation tissue in the folds becomes fibrous and eventually horny, showing as irregular, often pedunculated, bodies at the inner edge of the eyelids. In other cases there are nodular ac cumulations of small round cells in the lymph adenoid tissue of the retrotarsal conjunctiva, and in that covering the internal surface of the membrana nictitans, producing small lymph bodies or follicles which on eversion of the eyelids project as small, greyish-red millet-seed nodules.
This condition is known as follicular conjunc tivitis, and it is seen fairly commonly in the dog (Frohner).
Terminations and Complications. In a simple case with removal of the irritant recovery takes place within a few days. With infiltration and infection of the subepithelial tissue, as in papil lary follicular conjunctivitis, the condition is more likely to become chronic. As a result ectropion or entropion with trichiasis may often be brought about. In other cases, especially of the purulent type, there may be infection and consequent infiltration of the cornea leading to opacity and sometimes to ulceration. Chronic follicular conjunctivitis is also liable to be com plicated with corneal opacity and pannus (see"Keratitis"). From infection of the cornea the condition may spread to the anterior chamber and so a general ophthalmia be set up.
A further extension of the catarrhal change may reach the lachrymal sac and duct, so causing obstruction of the duct and a flow of tears over the face.
Symblepharon, the term applied to adhesion between the lid and the eyeball, is one of the results of severe membranous conjunctivitis, or a trauma or burn of the conjunctiva. During the healing process there is a great tendency for the bulbar and palpebral surfaces to adhere over a larger or smaller area. The movements of the eyeball are much restricted, and the adhesions, if they extend up to or beyond the corneal margin, may interfere with vision.
Treatment. The first step is to examine the eye to discover the presence of any foreign body, such as hay-seeds, oat-glumes, or grit. This is by no means an easy matter, but may be greatly helped by the use of a cocaine solution (1 per cent) applied by means of a spray or on a soft camel-hair brush. The foreign body may be embedded more or less in mucus or in the oedematous membrane, and is often difficult to dislodge. A probe, or the corner of a hand kerchief, or in the larger animals the handle of a teaspoon may be used for detaching the foreign body.
After extraction, the conjunctival sac must be irrigated with warm boracic acid solution, and in fact a preliminary flushing after cocain ization, but before manipulation is commenced, may wash out the irritant agent.
In those cases where some chemical irritant is operating, the application of a few drops of a bland oil such as olive-oil is to be advised, with or without the cocaine spray.
In purulent conjunctivitis the infective dis charge tends to accumulate deep down in the conjunctival sac, and it is important to wash out all discharge at each dressing. Frequent irrigation is the essential part of the treatment, and the choice of agent to be used is unimport ant as compared with the thoroughness and care exercised. Boracic acid solution 2 per cent (or about 10 grains to 1 ounce of water) is very useful, or perchloride of mercury solu tion (1 in 10,000) answers very well.
After irrigation astringent lotions may be used, and zinc sulphate (2 grains to 1 ounce), sodium hyposulphite (10 grains to 1 ounce), or silver nitrate (2 grains to 1 ounce) are recom mended. Care must be exercised in instilling these, or any other lotions, into the eye not to damage the eye. With a syringe or any instru ment a sharp movement of the animal's head may easily result in injury. It is best to take up the lotion with a little clean cotton-wool, and then, holding this vertically over the eye, to squeeze out the lotion and allow it to trickle in or over the eye.
Meanwhile, care must be taken to avoid infection either of the other eye, if only one is affected, or of other animals. In the case of horses it is best to avoid the use of halters and, unless a shade is required to be fixed and held in position, of headstalls, using instead a neck strap.
The stall or box, and particularly the manger, against which the patient has probably rubbed his eye, are likely to be infective and should not be used for other animals without disin fection. If there is any evidence or likelihood of an enzootic, healthy animals should be changed on to pasture in some other locality.
It is advisable, and adds much to the comfort of the patient, to darken the box or kennel, and a wet shade in the form of a piece of linen saturated with boracic acid solution, suspended from the headstall, over the eye helps con siderably in treatment.
In the more chronic types, such as papillary and follicular conjunctivitis, the application of the silver nitrate pencil to the hard folds or follicles is advisable at intervals of five to six days, whilst if the folliculitis is mainly on the membrana nictitans, as in the dog, the mem brane may be removed with advantage.
Whenever the caustic pencil is used it is advisable to neutralize any excess of the silver nitrate which may remain in the sac by flushing with normal saline solution. A harmless silver chloride is formed and the precipitate is removed by the excess of fluid.
Where fever accompanies acute conjunc tivitis some general treatment may be called for, such as the use of simple febrifuges, as ammonium acetate, or Epsom or Glauber's salts, in the drinking-water. In the dog a purgative may be given with advantage. The treatment of symblepharon is difficult and tedious. One operative procedure is to free the adhesions by dissection, and then lift up two conjunctival flaps adjacent to the raw surfaces. Each flap is cut rather long and narrow and is left attached at one end. By twisting it round on this narrow attached base it is made to cover one of the new raw areas, and sutured into position. The edges of the flap wound are brought together with fine sutures.
Chemical Burns of the Conjunctiva and Cornea.Probably the commonest agent to cause this injury is quicklime. Freshly lime washed buildings and stables are often respon sible for the production of stomatitis by animals licking the lime-washed parts, and in rubbing the head on such places injury to the eyes is not uncommon.
The degree of injury to the eye varies, but it is wise to assume it serious, for at first sight it will usually appear much less than will be seen to be the case in a few days' time. The con junctiva may be so damaged that a considerable raw surface will be left when the damaged cells are shed, and symblepharon is likely to result. The corneal epithelium may be so destroyed that although it looks clear at first a permanent opacity will be produced.
Treatment. For burns by acid substances the appropriate remedy is, of course, an alkaline lotion, such as per cent caustic potash or 2 per cent carbonate of soda. For alkalies a weak acid, such as z per cent tartaric acid, is best. The main line of treatment, however, is very thorough irrigation with water, and it is better to proceed with this at once than to waste time finding a chemical antidote. In the case of quicklime or any caustic powder it is important to wash out all particles which may be present, often in the depth of the subconjunctival sac or adherent to the surface of the cornea. A strong solution of sugar in water is very bene ficial in the case of quicklime after this pre liminary irrigation. The use of cocaine will generally be advisable, and the use of a bland oil, such as olive-oil, gives relief. Frequent irrigations with warm boracic acid lotion should follow.
Keratitis (Inflammation of the Cornea). The cornea from its position is especially susceptible to injury by external agents and also to bac terial invasion. This latter may occur directly, especially following some damage to the surface epithelium. It may also occur by extension from the infected conjunctiva, and in addition the cornea may share in scleral and uveal infections because of its blood supply.
Causes. Wounds of the cornea, injuries by foreign bodies, such as grass seeds, thorns, bits of chaff, or grit; chemical irritants, such as 3 For details see"Examination of the Eyes,"p. 743.
The hay bacillus (B. subtilis) is also a cause, and moulds such as aspergillus may also occur. In man the pneumococ,cus is often the cause of purulent ulcers and hypopyon.
Chronic sources of irritation such as entropion and trichiasis predispose to keratitis, and any purulent chronic infection in proximity to the cornea is a fruitful cause. The cornea is readily susceptible to any general impairment of vitality, and with such its powers of resistance are easily overcome. Thus in old age, or in very young animals, or in debilitated subjects, keratitis is very likely to occur. In certain specific diseases, notably distemper of the dog, and to a less degree influenza of the horse, keratitis is a common complication. Insects and nematode worms may also set up keratitis.
Symptoms. The earliest symptoms of kera titis are very similar to those of conjunctivitis, namely, lachrymation with a flow of tears over the face, photophobia, and more or less closure of the eyelids. When the eye is examined there is noticed a marked congestion of the vessels in the sclerotic immediately surrounding the cornea. The cornea itself may be quite clear and trans parent in an early case, but there is very soon evidence of more or less dense opacity. This varies from a mere haziness or filminess of the cornea up through a diffuse light blue but transparent infiltration to a dense white opacity. The opacity may be quite localized to the seat of injury—so as to be linear or speck-like, as in the case of injury caused by a whiplash— or the whole surface of the cornea may be involved.
Then again the surface of the cornea may be quite smooth, unabraded, and intact, or it may be ulcerated. It is of considerable practical importance to determine this point, and for this purpose examination may be made with a biconvex hand - lens, such as a reading - glass, or the lens supplied for use with the ophthalmo scope. The instillation of one or two drops of a solution of fluorescein (2 per cent) will make evident any surface abrasion or ulcer, since the stain only affects the damaged surface, staining it a brilliant greenish-yellow.
Lesions and Terminations. Following on any localized injury with infection, or on a bacterial invasion without injury, there is an infiltration of the inter-lamellar lymph spaces, so that these become more or less distended with fluid exudate, which may throw down a precipitate of fibrin, and closely packed with leucocytes. If this infiltration only involves the superficial layers, the cornea will appear mottled and often lustre less in patches due to swelling and lifting of the epithelium.
In a simple case the structural changes may go no further. With cessation of the injury, resolution begins, the outpoured lymph and dead cells are removed or absorbed, and the cornea again becomes clear and returns to the normal. In other cases the infiltration is deep seated (interstitial keratitis) and of a chronic nature. The opacity spreads until it covers a large part of the cornea, and along with the opa'city there is a formation of new blood vessels in the posterior layers of the cornea (pannus). These may be quite evident to the naked eye or only with a magnifying glass. In different cases the opacity varies greatly in density from a mere haze (nebula) to a dense white non-translucent opacity (leucoma). This variety of case, without any tendency to ulcera tion or abscess, is generally found as a sequel to debilitating diseases, such as distemper in the dog, or as a result of constitutional defects, causing malnutrition of the cornea. With im provement in general health the opacity may be gradually absorbed, though very frequently not completely. Often a deep opaque spot may be left in the centre of the cornea. In chronic cases in the dog an old opacity often becomes pigmented with a dense black pigment (melanin), usually at the periphery, but sometimes over a large part of the surface of the cornea. The pigmented opacity is never cleared up.
In a more acute case leucocytic infiltration is rapid. The leucocytes invade the infected corneal parenchyma in large numbers, and as a result of the bacterial toxic action many of these cells die, as do also the cells of the corneal tissue. Thus the lamellae and eventually the epithelial cells become necrosed and strip off, leaving an ulcer.
Sometimes a line of defence may be set up and outside this the leucocytes may remain active. In such a case the central area sloughs, leaving a clean-cut ulcer. With a more virulent infection, on the other hand, the ulceration extends both over the surface and also to the deeper layers. At one or more points in the floor of the ulcer, burrowing goes on until Descemet's membrane is laid bare. From in creased tension of the aqueous humour m the anterior chamber this elastic membrane may bulge out, looking like a transparent bead pro jecting out from the ulcer. After a time this usually ruptures, allowing of the escape of aqueous humour, or the prolapse and protrusion of the iris, and even dislocation and escape of the lens. The prolapsed iris caught in the edges of the wound is often bulged out on account of intraocular tension. The resulting mass, covered with a layer of lymph, which later be comes organized, is called a staphyloma.
In severe cases, even before perforation, the infection from what is really a corneal abscess spreads to the anterior chamber and reaches the iris. The aqueous humour becomes turbid from the presence of leucocytes and fibrin. The endothelium lining Descemet's membrane and covering the front of the iris proliferates and desquamates cells, and pours out an exudate so that there appears to be a collection of pus in the lower part of the anterior chamber, and fibrinous deposit is formed on the surfaces. This condition is known as hypopyon, and as a result the inflamed surfaces of cornea (posterior surface) and iris may adhere together (anterior synechia). With perforation and con sequent lessened tension the infection may be got rid of, and healing may commence. On the other hand, the infection may spread and panophthalmitis with complete destruction of the eye may result.
Following many severe cases of keratitis (and, as we have seen, as a complication of chronic follicular conjunctivitis) the condition known as pannus may be brought about, in which with a diffuse opacity there are numerous fine blood vessels running in over the cornea. Following the infiltration of the cornea, the vessels around its margin give off numerous capillary loops, and these spread in towards the centre under the epithelium. If an ulcer is present the vessels run in to its edges. During this time there may often be intense conjunctival congestion and also iritis. In other cases the vascularization of the scar occurs during healing and is accom panied by little pain.
In the healing of an ulcer the corneal cor puscles, acting like connective-tissue corpuscles, proliferate to fill up the defect in tissue with a modified connective tissue, fibrous and vascular. The epithelial cells at the edge of the ulcer grow in and strive to cover the defect. Any protruding part of a prolapsed iris will slough off. With time the scar tissue thus formed becomes somewhat less opaque and its fibres more regularly arranged and even laminated, but with an injury of any magnitude a per manent opacity is bound to result.
Where there has been no ulceration there is much greater chance of clearing, and after some months the vessels in a pannus may be so reduced as to be invisible to the naked eye, although a haziness of the cornea will still be evident.
Treatment. An examination of the cornea should first be made to determine the presence, if any, of a foreign body on or embedded in its substance. A brown rust stain round about the wound will be seen if a particle of iron or steel is the offending body. For removal it is necessary as a rule to use cocaine, or even a general anaesthetic in the larger animals, in order completely to control movement of the eye, and then a spud or blunt needle or a small curette may be used. After removal, or even before this is attempted, especially if the foreign body has penetrated into the anterior chamber, an antiseptic eye lotion, either boracic acid or perchloride of mercury (1 in 10,000), should be used to wash away mucus and dis charge and lessen the risk of infection. If there is danger of pushing the foreign body into the anterior chamber during the attempt at removal, a flat keratome should be inserted into the cornea behind it, so giving a firm support. The subsequent treatment is as for a corneal wound or ulcer.
In all cases of keratitis it is important to determine the presence of any abrasion or ulcer by means of fluorescein, and in case such is found, lotions containing lead salts or permanganate of potash should be avoided—the former agent because an insoluble lead albuminate is formed and a chronic opacity results; the latter because with this lotion the cement substance between lamellae appears to be dissolved and the ulcer quickly spreads and deepens.
Where there is no wound, but only opacity due to infiltration, the indications are for antiseptic lotions to be used frequently, followed at each dressing by some stimulant astringent agent to promote absorption and improved tone. Such agents are silver nitrate to 1 per cent in distilled water, zinc sulphate in the same strength, or sodium hyposulphite 2 per cent. Ointments of yellow oxide, or nitrate of mercury (10 grains to 1 oz. of vaseline), may be smeared inside the lids night and morning with good effect. General treatment by tonics, such as iron, quinine, strychnine, or arsenic, and im proved diet, is important: in fact, any measures to improve the circulation and general constitu tion.
Where there is a wound or ulcer, treatment should be directed to the prevention of com plications, such as perforation with prolapse of the iris and subsequent synechia or staphyloma. Atropine solution should be at once instilled to withdraw the iris so that, if perforation occur, it is out of harm's way. The suggestion is sometimes made that myotics, such as eserine, should be used because of a supposed effect in lessening intraocular tension. This lessening of tension is by no means a certain effect of myotics, and the added risk of iris prolapse in all except marginal corneal ulcers is of much greater importance. Further, with corneal ulcer there is often iritis and more or less hypopyon, and here again atropine should be used.
The ulcer itself is treated by means of the usual antiseptic lotions, but with any tendency to spread or become purulent it will require special methods.
Its surface may be disinfected by means of tincture of iodine or hydrogen peroxide, applied by means of a fine camel-hair brush, or pure carbolic acid applied on a fine piece of wood such as a match—the excess being carefully wiped away. An insufflation of finely powdered calomel on the surface may also prove beneficial. In the human subject the galvano-cautery is frequently used for the same purpose. A very useful agent in severe keratitis with or without ulceration is dionine—a morphine derivative— which causes considerable vascular dilatation with chemosis, and a flow of lymph. Dionine is used in 5 per cent solution and instilled on alternate days.
With a spreading or deep ulcer threatening perforation, or where hypopyon is present, it is often of great advantage to anticipate the perforation by performing the operation of paracentesis or tapping of the anterior chamber. This can be done with a small keratome or a narrow-bladed knife, which is passed through the cornea obliquely to the surface, entering at a point 2 or 3 millimetres outside one edge of the ulcer. The blade traverses the anterior chamber in a plane parallel to and in front of the iris, and emerges 2 or 3 millimetres on the further side of the ulcer margin. The blade is then turned outward and cuts through the cornea so as to divide the saucer-shaped ulcer in two. The aqueous humour and any hypopyon escape, and in order to avoid prolapse of the iris the outward cut should be made very slowly, whilst atropine should be used before the operation. Such procedure lessens pain, pro motes healing of the ulcer, and leaves a slight linear scar much less objectionable than the large scar, synechia, and possible staphyloma produced by natural perforation of the ulcer. If perforation has already occurred the iris may be already prolapsed and involved in the ulcer. In such a case there is grave danger of infection spreading to all parts of the eye through the infected iris vessels. Any adhesions between the prolapsed iris and the wound edges must be gently broken down with a probe, the iris drawn a little further forward in the wound and, after efficient disinfection, cut off flush with the surface of the cornea. The iris may now be pushed back through the wound into the anterior chamber by means of a probe or blunt needle. If panophthalmitis results, ex tirpation of the eyeball is the only treatment. In cases of staphyloma evisceration of all the structures inside the sclerotic is a useful opera tion because of the freely movable stump which is left on which to insert an artificial eye. Thorough disinfection of the cavity is called for, and the wound is drawn together with sutures.
Many cases of keratitis, especially if compli cated with iritis, are benefited by subconjunctival injections of 4 per cent saline solution. The injection of from 10 minims in the dog to 1 drachm in the horse is made under the bulbar conjunctiva outside the sclerotic, the needle being directed away from the cornea. Con siderable pain results and a good deal of injection of vessels and even chemosis, so that it is advisable to use a cocaine lotion before the saline injection is made. The vascular dis turbance and stimulation is the probable explanation of the beneficial results, and a second injection should not be made until the reaction of the former one has subsided.
Warm fomentations to the eye and the application of a pressure bandage are to be recommended in the routine treatment of corneal ulcers or abscesses, since they not only relieve pain but promote resolution and healing and tend to prevent perforation.
They are contra-indicated only when there is purulent conjunctivitis as a complication, in which case no dressing which retains the discharge must be used. The dense opacities and scars which are left after serious keratitis, ulcers and wounds, tend, if unpigmented, to contract and become thinner. With vasculariza tion and connective-tissue formation of any magnitude in the cornea, however, the opacity is permanent. Its effect on vision depends on its extent and position. If marginal and of small extent, the opacity causes little incon venience in an animal, though it is a blemish and disfigurement. If central it is much more serious. The use of the silver nitrate pencil is to be recommended for promoting reduction of a localized but prominent scar. The application of pure carbolic acid to a localized vascular patch may also assist in clearing it up.
Tattooing with Indian ink by means of a fine needle may be used to hide the blemish caused by a dense white opacity. Iridectomy (q.v.) so as to enlarge the pupillary opening may be practised with benefit to the sight where the opacity is central or affects only parts of the cornea. The iris opposite to the clear corneal area is removed so that light enters there and sight is restored to an otherwise blind eye.
VII. Diseases of the Uveal Tract The uveal tract is made up of the iris, the ciliary body, and the choroid. These three structures are very intimately connected with one another, are very similar histologically, and have the same blood supply. The consequence is that in all cases of severe iritis there is some degree of inflammation of the ciliary body (cyclitis), and infection may easily spread to the choroid, though this is not so common. Thus there may be the three conditions: Iritis. Inflammation of the iris.
Cyclitis. Inflammation of the ciliary body.
Choroiditis.Inflammation of the choroid.
Causes. Iritis may be primary, occurring as an independent condition or as a complication of or sequel to some systemic disease, or it may be secondary to an infection of the conjunctiva or cornea. In either case the ciliary body may be, and commonly is, involved when the condition is known as irido-cyclitis.
Primary iritis or irido-cyclitis is seen in its most characteristic form in the disease known as periodic or specific ophthalmia of the horse (q.v.).
It may also occur as a complication in cases of influenza and purpura haamorrhagica in the horse, after acute febrile diseases in cattle, or distemper in the dog. It is definitely associated with rheumatism in the human subject. In flammation of the uveal tract, iris, ciliary body, and often choroid as well, is, however, much more commonly due to an extension of infection from conjunctivitis or keratitis, especially with an ulcerated perforated cornea.
Similarly wounds of the cornea or sclerotic, with prolapse of iris or choroid, provide an easy entrance for infection to the uveal tract. This affords one urgent reason for preventing the inclusion of portions of iris or choroid in a healing wound or ulcer, since these very vascular structures facilitate infection.
Symptoms. With inflammation of the iris and ciliary body there are from the beginning lachrymation and photophobia, although these are often not as marked as in affections of the cornea. The eyelids, however, are kept more or less closed, and the animal seeks a shady place. It may soon be evident that there is some dimness of vision, although that being sub jective is not easy to determine. On examination of the eye certain characteristic points may be noticed. There is congestion of the ciliary vessels in a narrow ring just outside the limbus of the cornea. If uncomplicated with con junctivitis or there is no discharge from the eye. The iris itself is seen to have a somewhat dull appearance; its lustre is lessened, and its colour changed to a murky yellow. The pupil is contracted and the iris immobile, not reacting readily to light reflexes. At first this contracted pupil is due to spasm of the sphincter muscle of the iris, but with a throwing out of inflammatory exudate from the inflamed iris adhesion takes place between the posterior surface of the iris and the lens (posterior synechia), and the contracted pupil is permanent. The aqueous humour is often rendered turbid by the pouring out of inflammatory exudate, and an appearance simulating hypopyon results from the deposition of jelly-like lymph clots in the anterior chamber. The cornea itself is often dim and blurred because of this lymph on its posterior surface.
A comparison with the normal iris of the sound eye is always advisable in any early case of iritis if there is any doubt about the condition.
Iritis is a painful condition. The animal hangs his head, avoids light, may show some general symptoms of loss of appetite and some rise of temperature. It must always be con sidered a serious condition, whether arising primarily or as a complication of conjunctival or corneal disease.
Terminations. The results of iritis may be serious. Posterior synechia—the adhesion of the inflamed iris to the anterior surface of the lens—is a common result, and it affects the subsequent mobility of the iris, so interfering with the entrance of light into the eye. It may be detected by the use of atropine, for the pupil fails to dilate. If the adhesions are only partial, the iris is retracted where free, but fails to be withdrawn where attached, so that an irregular-shaped pupil is seen. Where the adhesions are complete all round the pupillary margin no retraction of the iris is possible, and the condition is one of complete synechia. By interference with the normal drainage of the aqueous humour this condition may lead to that of glaucoma, with blindness as a result.
Irido-cyclitis is likely to be followed by some blurring of the cornea by the deposition of inflammatory exudate or lymph on its posterior surface (keratitis punctata). Further, disease of the ciliary body has a serious effect on the nutrition of the lens, and as a consequence of cyclitis cataract is very commonly produced. Purulent choroiditis pointing to a serious intra ocular infection is likely to be followed by panophthalmitis, with destruction of the eye.
Treatment. When iritis or irido-cyclitis is diagnosed active treatment must be undertaken at once. Atropine—whether in 1 per cent solution of the sulphate in water, or as a 1 per cent ointment, or in the form of lamellm—is to be applied early and continued throughout the treatment. Its effect is to paralyse the sphincter iridis and so give rest to the muscle. It also lessens hyperaemia and exudation by lessening the surface area of the iris, and by dilating the pupil it withdraws the anterior edge of the iris from contact with the lens and so prevents the possibility of synechia. If adhesions have just commenced to form they may be broken down by pushing the use of atropine solution, a few drops at intervals of five minutes, over a period of half to one hour, so that its effects are kept up at full strength. Sometimes the skin of the eyelids may be irritated by the frequent use of atropine, and to prevent this the lids should be lightly smeared with vaseline before using the lotion.
The patient should be kept in a shaded or darkened place throughout the treatment. Hot fomentations over the orbital region have a soothing effect. A purgative is advisable at the onset. If the condition is thought to be due to rheumatism, salicylates must be given. Where lymph is thrown out into the anterior chamber it will probably be found necessary to operate for its removal. In severe cases the subeonjunctival injection of hypertonic saline solution (4 pet cent), or of Lugol's solution of iodine, is a measure which should be tried. The injection should be preceded by the use of a few drops of cocaine solution into the eye. It is made by means of a fine hypodermic needle inserted under the bulbar conjunctiva outside the corneal margin, the needle being directed away from the cornea. In the horse or ox one or two drachms of the salt solution should be injected, in the dog from 5 to 20 minims, and the injection should not be repeated until the reaction following the first injection has sub sided. Of Lugol's solution the amount to be injected should not exceed 2 c.c.
In cases of suppurative choroiditis or pan ophthalmitis evisceration of the contents of the eyeball is the best procedure. Complete enucleation of the eyeball whilst there is con siderable virulent infection is often dangerous, as there is a chance of meningeal infection from the orbital cavity.
Periodic Ophthalmia of the Horse.This con dition, known as periodic ophthalmia from its extraordinary tendency to recur again and again, specific ophthalmia because it occurs as a primary affection irrespective of any other disease, and moon-blindness because of its periodicity, is peculiar to equines. It is essentially an inflam mation of the uveal tract, especially the iris and ciliary body.
Causes. The etiology of this disease is very little understood. In Great Britain and in Australia the condition must be considered dis tinctly rare in normal times. During the war many more cases than usual have been seen, and there can be little doubt that the congre gating of a large number of horses on board ship or in camps has a marked effect in pro ducing the disease. In any case, periodic ophthalmia is much less common nowadays than it was fifty years ago. There is ample evidence that the disease used to occur almost as an enzootic in many old coaching stables in the days of the mail-coach. Improved sani tation of stables, and especially increased light and plenty of fresh air, have had a very material effect in lessening the number of cases. A climatic factor of some importance is that of damp surroundings and wet weather. Swampy districts, such as the fens, parts of Ireland, Holland, and during the war Flanders, provide many more cases than dry uplands. Again, poor feeding and hard work leading to a debili tated condition render horses more susceptible than those in good condition, although debility is by no means an essential condition. Heredity has been blamed, although it is extremely difficult to see how it can have any effect what soever.
Much investigation work has been done to discover a specific micro-organism, though so far without any definite accepted result. Various bacilli and strepto- and staphylococci have been obtained from eyes affected with periodic ophthalmia, and in some cases pure cultures of these organisms when inoculated into healthy eyes have produced irido-cyclitis with symptoms similar to the original disease. Such an experi ment is by no means convincing, and it would require to be shown that the iritis produced showed recurrence or periodicity as a prominent feature as well as other characteristic effects before the culture nsed could be considered a sufficient cause of the natural disease. When it is remembered that syphilis, gonorrhoea, and rheumatism are the commonest causes of recur rent iritis in man, it appears likely that periodic ophthalmia of the horse is really a sign of a general infection rather than a merely local one. It is not the common experience that the disease is markedly contagious. As a rule, the cases are isolated ones, with a large number of unaffected horses in the stable or camp.
The age incidence is probably a coincidence rather than the effect of any special age sus ceptibility. Four- and five-year-old horses would probably be found to furnish the largest number of cases in civil practice, for the reason that they are at that age first congregated into close, ill-ventilated stables.
Symptoms. In its physical signs periodic ophthalmia is simply an irido-cyclitis, with sometimes choroiditis. The condition may be acute, but is usually subacute in character. The onset is sudden. Usually the first indica tion of any disease is to find the horse in the morning with half-closed eyelids on one side, with a trickle of tears down the face, and avoid ing any bright light. On examination the eyeball is seen to be somewhat sunken, the horse objects to manipulation, and on attempting this the lids are tightly closed. There is more or less conjunctival congestion, but usually marked ciliary congestion just outside the corneal lirabus, whilst the pupil is contracted. The animal's temperature may be raised a little, sometimes as much as three or four degrees, and the appetite is sometimes affected. After such an onset the characteristic signs gradually develop.
The iris loses its lustre, looks dull and of a murky yellow colour; the aqueous humour becomes more or less turbid at first, whilst within a day or two a mass of coagulated and often blood stained lymph comes to lie at the bottom of the anterior chamber. The cornea is more or less blurred, and fine blood-vessels may be seen in the corneal area running in from the ciliary vessels. This period of inflammation may last from two or four up to ten days. The condition is a painful one; it affects, as a rule, only one eye, and a comparison with the sound eye makes the abnormalities of the affected one the more evident. After this first stage there is a gradual decline of all the symptoms. Lachrymation and photophobia lessen, the anterior chamber clears up, exuded lymph, if not very large, in amount, is absorbed, and the iris becomes mobile once more. Thus the eye returns almost, if not quite, to the normal condition. There is often left some slight steaminess of the cornea, and the lustre of the iris may not be quite so clear as in the sound eye, but only a close inspection will detect the difference. The whole period of the attack is usually from two to three weeks. Then occurs the characteristic recurrence. The second attack may be in the same eye, or it may often pick out the other one. It occurs in from two to three weeks to as many months after the first attack. In this second attack the symptoms are much the same as before, but resolution after the attack is not so com plete. After two or three attacks the cornea may show some permanent vascularization round its outer edge, the iris will probably have con tracted some adhesions either to lens or cornea, so that the pupil when dilated has an irregular border, and the lens will usually show the white specks of early cataract. After several attacks the lens shows a number of fleecy lines running in towards the centre, and soon the whole crystalline substance has become a white opaque mass, and the animal is now quite blind. The later attacks are usually of shorter duration than the first one, but each adds to the per manent defect left in the eye. In eyes which have been attacked several times, on post mortem it is usually found that the vitreous humour is of a faint yellow to an amber colour and lessened in amount. The choroid may be thickened, often in patches, the lens or its capsule opaque, and there are the usual changes due to irido-cyclitis.
Treatment. Something can be done in the way of prevention by an understanding of the predisposing causes. In fact, in civil life im proved stable hygiene has made the disease a comparatively rare one. The affected animal should be placed in a roomy, shaded, but well ventilated box, or if in the open should be provided with an eye-shade. Atropine should be used from the commencement, and a spray consisting of atropine sulphate 5 grains, cocaine hydrochloride 5 grains, and boric acid 10 grains to 1 oz. of distilled water, is very useful. The horse should have a dose of physic, and thereafter should have light laxative diet and little corn. Fomentations give relief during the inflammatory stage and quicken the clearing-up process. Subconjunctival injections of hyper tonic saline (4 per cent) should be used in the early stages as soon as the atropine solution has had time to act. An alternative method is that described by Wiggs, and reported on favourably by Chambers,' in which 1 c.c. of Lugol's solution of iodine is injected through the skin over the supraorbital fossa deeply into the supraorbital fat. The skin is disinfected, the needle inserted to a depth of half an inch or a little more, and the injection made. A second injection, whether subconjunctival or interstitial, should not be made until the reaction caused by the first one has subsided—usually in three or four days' time. In an outbreak of specific ophthalmia in cattle in Rhodesia in 1913, Chambers reports the result of this treatment in a hundred cases."Sixty-three were cured by the first injection, twenty-six had two injections, and eleven did not improve."The treatment of such compli cations as arise—synechia, hypopyon, etc. is as described under"Iritis." Iridectomy.The operation for the removal of a portion of the iris is performed either to allow of the entrance into the eye of light rays in cases where entrance through the pupil is prevented by a central cataract or a corneal opacity; or to reduce abnormally high intra ocular tension such as occurs in glaucoma; or for the purpose of removing a foreign body embedded in the iris.
The operation consists in removing a small portion of the iris, so providing an opening or coloboma in the iris ring, through a corneal incision. The size of the coloboma has to be determined by the object for which the opera tion is performed. For optical purposes a narrow coloboma is preferred in order that too much light should not enter the eye, but for glaucoma the opening should be wide. The width is dependent on the length of the corneal incision. In the dog the opening is best made in the lower internal quadrant.
The animal being anaesthetized and a specu lum applied, fixation forceps. are put on just outside the corneo-scleral margin at a point opposite to where the coloboma is to be. The corneal incision may be made either with a keratome or a Graefe knife, but in either case the knife must be sharp. Using a keratome, the knife is inserted into the cornea, and when the point is in the anterior chamber the blade is directed parallel to the cornea and iris as near to the deep surface of the cornea as possible, so as to avoid injury to the iris or lens. When the corneal incision is wide enough the knife is slowly withdrawn and aqueous humour allowed to escape. The anterior chamber thus becomes shallower and the iris and lens come forward. The portion of iris to be removed can now be withdrawn through the corneal incision with iris forceps or a Tyrrell's hook. The closed forceps or hook are passed into the anterior chamber, and when the points are near the pupillary margin of the iris they are opened widely to catch up the iris and withdraw it. The desired amount is then snipped off with fine curved scissors, the incision being in the radial direction. No tags of iris should be left in the corneal wound, and any irregularity or folding of the edges of the coloboma should be reduced by careful smoothing with a blunt needle or spatula. This toilet of the iris is an important factor in the success of the operation. A dressing and bandage are then applied and the wound treated in the ordinary way.
VIII. Diseases of the ScleroticViii. Diseases of the Sclerotic These are very uncommon except as a result of direct injury. Marked congestion of the vessels running over the white part of the eye (sclera) may often suggest inflammation of the sclera, or sderitis, but in fact this condition is uncommon and ill-defmed. The congested vessels are either concerned in bulbar conjunc tivitis, in which case they are movable over the apparently affected sclera, so proving them to be conjunctival, or they are confined to a narrow band just outside the limbus of the cornea, in which case they denote ciliary congestion and point to inflammation of the iris and ciliary body.
Wounds of the sclera are serious in that they often allow of prolapse of the choroid, or of the iris, or of escape of vitreous humour. They may also allow of infection of the interior of the eye and so set up panophthalmitis.
Treatment. A careful examination under cocaine is called for to determine the extent of the damage. A simple wound should be sutured after disinfection of the conjunctival sac and exposed sclerotic. If parts of the choroid or iris are prolapsed the adhesions, if any, must be carefully separated from the wound edges, infected and damaged parts snipped off with scissors, the wound disinfected and sutured. This procedure will usually require a general anaesthetic. After operation a dressing and bandage should be applied.
If the damage is extensive, or the ocular contents have escaped through the wound, or in cases where intraocular infection has certainly occurred, the eyeball should be excised.
The vitreous humour is subject to very few diseased conditions, and these are usually the result of extension from the choroid, ciliary body, or more commonly the direct result of wounds or the presence of foreign bodies.
Abscess. Pus in the vitreous humour may result from spreading infection in a case of purulent choroiditis. Such a condition soon extends to other neighbouring structures, and panophthalmitis is the result.
Haemorrhage.Blood may be poured out into the vitreous as a result of a blow on the eye. When the swelling of the eyelids and surround ing parts has subsided the animal may be found to be blind. The pupil is dilated, but on throw ing a beam of light into the eye with the ophthal moscope no light reflex is seen and the pupil remains black and unilluminated. If only a small amount of blood has been thrown out it will show up as black spots with illuminated areas around them.
Absorption of small deposits of blood may take place, but with the vitreous full of blood no cure is possible.
Foreign Bodies in the Vitreous.The effects will vary, depending on (1) whether infective material containing micro-organisms entered with the foreign body, and (2) on its composition.
With infection there is likely to be an ex tension until panophthalmitis occurs. If the foreign substance be a piece of iron or steel, rust will be formed and discoloration of the vitreous and iris and other structures will follow. Usually an intense inflammation will be set up.
Other substances, such as a lead pellet, also usually cause inflammation when lodged in the vitreous, and it is in these cases particularly that the condition known as sympathetic oph thalmia (q.v.), affecting the other or sound eye, is to be feared as a sequel.
Foreign bodies in the vitreous may be dia gnosed by the appearance and history of a wound of the cornea or sclera, by using the ophthal moscope, or, in the case of many metals, by means of an X-ray apparatus.
Treatment. When ophthalmitis threatens, the eyeball should be excised. Foreign bodies may sometimes be removed successfully through a scleral incision which allows an escape of the vitreous carrying with it the foreign body. In the case of iron and steel particles an electro magnet can be used to draw them out, or, at any rate, into the anterior chamber, from which they can be removed. If a foreign body is known to be in the vitreous and cannot be re moved, it is advisable to enucleate the eyeball.
Sympathetic ophthalmia is a condition of general plastic inflammation of the uveal tract of one eye arising as a result of uveitis of the other eye. The two eyes can be distinguished as the first and the second eye, or as the exciting eye and the sympathetic eye.
Pathology. — The pathology of sympathetic ophthalmia is not understood. It is remarkable that the condition is specially liable to occur after perforating wounds involving either anterior chamber or vitreous humour of the exciting eye. On the other hand, the condition does not follow a purulent uveitis or panoph thalmitis due to infection with pyogenic organisms. Again, blows and injuries to the eyes without rupture of the conjunctiva do not bring about sympathetic ophthalmia in the second eye. Thus the evidence points to a specific infecting agent as the cause, but not a pyogenic organism.
At a varying period after the injury setting up ophthalmia in the first eye, it may be weeks or months, the symptoms of iritis or irido cyclitis and choroiditis are seen in the second eye, occurring without any obvious cause.
Treatment. The condition is not common in the domesticated animals, but the following rules should be observed in dealing with an eye affected with a perforating wound, so as to lessen the risk to the second eye: (1) If the injury has destroyed the sight of the eye, the organ should be removed. This will effectively prevent any danger to the other eye.
(2) If sympathetic ophthalmia has already commenced in the second eye, on no account remove the first eye if possessed of any sight at all.
The treatment of the affected (sympathizing) eye is as for uveitis in general.' Panophthalmitis is the term applied to a general suppurative inflammation of the internal structures of the eye following septic infection. It is possible for the eye to become infected as the result of a general blood infection with pywnaia, but this is very rare, and the local condition would be overshadowed by the general constitutional symptoms of septic poisoning. For practical purposes panophthalmitis is caused by local infection through a wound. A perfor ating wound of the eye, the result of an injury with the implantation of pyogenic organisms at the time of the injury, is a very common cause. The entrance of organisms as a result of ulcera tion of the cornea following keratitis, or infec tion following a surgical operation such as para centesis or a cataract operation, or iridectomy, may also be the cause of panophthalmitis. The offending micro-organisms are usually strepto cocci, but other pus-producing organisms may also be present.
Symptoms. As a result of the infection there is considerable pain, photophobia, and excess ive lachrymation. The eyelids are markedly swollen, and there is more or less chemosis. The cornea speedily becomes opaque, and the globe is generally swollen as a result of cedema and its pus contents.
In a short time the whole contents of the eye are involved in the suppurative process and more or less broken down (phthisis bulbi). The discharge is muco-purulent and blood-stained, often offensive. With opening up of the original wound or rupture of what is now an abscess cavity the broken-down contents of the globe will escape. Following this collapse of the eyeball the acute inflammation will usually gradually subside, the discharge become less, and the wound heal by granulation. The result is a shrunken, sightless globe, usually painless, but sometimes remaining irritable and a con stant source of trouble.
In a less favourable case infection may spread by the ophthalmic veins to the venous sinuses and so to the meninges, or a general septic infec tion with pymia or septicaemia may be set up.
Treatment. — When panophthalmitis is de finitely present it is unlikely that any treatment will avail to save the eye. Hot fomentations to the eye and irrigation with 1 per cent creolin solution will help to lessen the pain and get rid of the discharge, but the only choice is between enucleation of the whole globe or evisceration of its contents. Some surgeons refuse to excise the eyeball whilst the acute suppurative process is still going on, because of the risk of setting up septic meningitis. In this case evisceration may be practised. This risk is not, however, a very serious one, and it is undoubtedly better in the great majority of cases to proceed directly to excise the eyeball.
Excision or Enucleation of the Eye.The animal having been all discharge is thoroughly washed away by means of plentiful irrigations with sublimate solution (1 in 5000) or sterile saline, the eyelids are cleansed, and a speculum inserted. The globe is seized with a pair of fixation forceps and an incision is made in the conjunctiva all round the corneal margin. The bulbar conjunctiva is now separated from the globe with scissors and forceps, and a blunt hook (a strabismus hook is the best in the dog, but is too small in the horse) is passed under each of the ocular muscles in turn so that they may be cut through as near to their insertion to the eye as possible. Pressure is then put on the speculum so as to make the eyeball bulge forward, and with a pair of rat-tooth forceps one of the muscle insertions is seized and the globe drawn forward. A pair of probe-pointed curved scissors are now passed back behind the globe so as to divide the retractor muscle and the optic nerve as far back as possible. To avoid any chance of infection the orbital cavity should now be thoroughly irrigated with hot sublimate solution (1 in 5000) or hot sterile saline solution. This will at the same time control any haemorrhage. A small pledget of gauze is left in the cavity and retained by a suture uniting the eyelids. An outside dressing and bandage may be put on if thought necessary. The cavity should be irrigated and the dressing reapplied daily for a few days.
When all discharge has ceased and the stump has become firm, say in about six or eight weeks' time, an artificial eye may be put in. Otherwise the margins of the eyelids may be pared and then united by means of sutures. It is advisable to leave a small space at the nasal canthus unsutured at first to allow of the escape of any discharge. When the cavity is quite certainly dry this space may be closed up.
X. Glaucoma Glaucoma is a condition of which the patho logy is somewhat obscure, but in which the essential symptom is increased intraocular tension. The increased tension is due to an overfulness of the globe with an excess of aqueous humour. The eyeball is consequently harder or firmer to the touch than normal, and the increased pressure can be determined either by the educated sense of touch in the surgeon or more accurately by an instrument called a tonometer, which measures the depression pro duced by resting the instrument on the cornea whilst placing graduated weights in the scale pan. Glaucoma may be primary when it comes on without any antecedent definite recognizable disease of the eye, or secondary when it arises as a sequel to some previous eye disease or inj ury.
Etiology. Normally the aqueous humour is constantly being secreted or expressed from the blood and as constantly being removed by the lymphatics and veins adjacent to the anterior chamber, so that the amount remains fairly constant. With continued secretion but non removal the amount increases and the intra ocular tension rises, so causing glaucoma.
The chief channel of exit for used-up aqueous humour is through the network or open spaces (spaces of Fontana) in the suspensory ligament (zonula of Zinn) of the lens. This zonula or suspensory ligament consists of delicate fibres running from the ciliary processes to the equator or edge of the lens, and between the fibres are spaces communicating with the anterior chamber and thence, with a barrier of endothelium only, with the sinus venosus sclerce or canal of Schlemm. This is a circular venous sinus near the corneo-scleral margin. The mechanism of the exit of excess of aqueous humour depends, therefore, on the patency of the angle of the anterior chamber, and if this angle is closed up the removal of fluid is at once prevented. In glaucoma the root or periphery of the iris is pressed forward and lies close up against the periphery of the cornea, so closing the angle. Priestley Smith has suggested that in many cases there is a too small circumlental space, and this agrees with the observation that small eyes are more often affected with glaucoma than those of normal size. The progressive increase m the size of the lens with age may thus account for glaucoma in old age. Any great increase of blood pressure, local or general, causing a con gestion in the uveal tract and an excessive pro duction of aqueous humour will also help to produce the condition.
Primary glaucoma usually affects both eyes, although the onset may not always be syn chronous. There are two types, the chronic and the acute.
Simple Chronic Glaucoma. is gradually increasing dimness of vision, but as the condition comes on slowly and insidi ously this is often unnoticed for some consider able time in animals. Gradually the intra ocular tension increases, but the external appearance of the eye is normal and the pupil may continue to react. On examining the eye with the ophthalmoscope the characteristic sign is the cupping of the optic disc, This occurs because the lamina cribroscc—the opening in the sclera through which the optic nerve enters— is the weakest part of the globe and becomes bulged out by the rise in pressure. This cup ping of the optic disc causes the retinal vessels to look as though broken off at the margin of the papilla where they pass round the over hanging edge of the cup. Pulsation of the arteries may often be seen in the glaucomatous eye, because the increased pressure produces a resistance to the pulse wave.
The disease gradually progresses, and if left untreated eventually ends in total blindness.
Acute Glaucoma. — This comes on quite rapidly, and is accompanied by definite signs. There is high intraocular tension with dilata tion and immobility of the pupil and congestion of the ciliary vessels, especially the veins. The cornea is more or less insensitive, the anterior chamber appears shallow and the iris pattern somewhat indistinct. Opacity of the cornea or a characteristic"steaminess"is brought about by oedema of its substance.
The acute symptoms may pass off in a few days, but the recovery is never quite complete. After an interval of a few weeks a second attack occurs, leaving the eye worse than before, and with two or three recurrences blindness ensues.
Primary glaucoma is a very rare condition in animals. It is doubtful if it ever occurs in the horse, but cases have been recorded in the dog. Moller states that he has never observed actual cupping of the optic disc in animals, but only a general condition of hydrophthalmos, Secondary glaucoma arises as a sequel to other diseased conditions of the eye, usually of such a nature as to bring about a closure of the angle of the anterior chamber. Such conditions are complete posterior synechia, ulcers or wounds of the cornea with prolapse of the iris into the wound, dislocation of the crystalline lens into the anterior chamber, traumatic cataracts lead ing to swelling of the lens, intraocular tumours such as choroidal sarcoma or a glioma, and advanced irido-cyclitis.
Treatment. The only successful treatment of glaucoma is by means of iridectomy (q.v.). The removal of a portion of iris, advocated for this purpose by von Graefe in 1857, has for its object the opening up of a path for the draining away of the excessive fluid in the anterior chamber. In a successful operation a sclero-corneal fistula is produced and a small portion of the root of the iris opposite the coloboma becomes folded up and rests in the wound, so keeping the channel patent. The ordinary myotics—eserine and pilocarpine—may be used with some slight advantage to lessen intraocular tension, but their action is temporary and purely palliative. Purgatives should be given in any acute case, and the animal should be restricted in diet.
XI. Disease of the Crystalline Lens Structure.The crystalline lens is an epithelial structure enclosed in a structureless elastic mem brane or capsule, and suspended in the eye by means of the suspensory ligament or zonula of Zinn. The lens is a biconvex body situated in front of the vitreous humour, and behind the iris, which is in partial contact with its anterior surface. The substance of the lens consists of a central denser portion or nucleus, and a softer cortical portion. When hardened the lens sub stance is seen to be made up of a mass of fibres united to form concentric layers arranged like the layers of an onion.
The lens contains neither vessels nor nerves.
The capsule of the lens, though spoken of as an anterior and posterior capsule, is really a continuous covering, and regulates the nutri tion of the lens substance which takes place by osmosis. The anterior portion of the capsule is lined with flat polygonal cells forming an epithelium on its lental or inner surface. This is the only portion of the capsule capable of proliferation.
The suspensory ligameat or zonula is made up of delicate fibres which reach from the ciliary processes to join the lens capsule at the equator of the lens. The fibres of the ligament form an open network with spaces (spaces of Fontana) which contain aqueous humour and communi cate with the posterior and anterior chambers.
The interval between the ciliary body and the lens is known as the circumferential or circum lental space.
Diseases of the Lens. The lens is not capable of undergoing any active inflammatory process. What changes occur are of a degenerative nature and are known by the name of cataract. Apart from cataract the only diseases of the lens are congenital defects or abnormalities, and dislo cation due to injury or disease of other eye structures.
Cataract. Degeneration of the lens giving rise to opacities in that structure is known as cataract. Proliferation of the anterior capsular epithelium results in the condition known as capsular cataract.
Cataract is common in the horse and dog, but is also found in other animals. Wild animals in captivity appear singularly prone to the dis ease, and such is seen particularly in kangaroos and wallabies.
Pathology. Since cataract is a degenerative condition, it will be easily understood that it occurs most frequently as a senile change. Further, any failure or irregularity in the nutri tion of the lens is likely to be followed by cataract, so that disease in the adjacent struc tures, such as irido-cyclitis, glaucoma, intra ocular tumours, and any damage to the capsule of the lens, are common causes. Constitutional disease may also affect the nutrition of the lens, and this is exemplified by the frequent occur rence of cataract associated with diabetes (glycosuria).
There can be little doubt that the conditions predisposing to cataract are frequently inherited, for congenital cataracts are not uncommon, and there is sufficient justification for the view that cataract may be in some cases hereditary, so that breeding from animals the subjects of non traumatic cataract is inadvisable.
Cataracts may be classified as primary when they are either senile or congenital, or due to a constitutional defect such as diabetes; or secondary when they result from some disease of other structures in the eye, or from trauma involving the lens capsule. Further, from the surgical point of view cataracts are also classi fied according to whether the change in the lens is stationary or progressive, and according to the density and position of the opacity. An incipient cataract is one in which the change is just beginning and is not associated with much impairment of vision. Such a condition is progressive and passes on gradually to the stage of a mature cataract in which the lens has undergone complete degenerative change. In this stage illumination of the eye with the ophthalmoscope gives rise to no bright reflex from the fundus and no glittering sectors in the cortex of the lens, for the whole lens is opaque.
A mature cataract may remain stationary in that condition, or it may go on to become hypermature, in which case there is often soften ing of the outer degenerated cortex, whilst the nucleus becomes dry, hard, and chalky. In this stage dislocation of the lens is apt to take place either into the anterior chamber or into the vitreous.
With regard to position, cataracts may be nuclear when the change begins in the centre of the lens, polar when the change is cortical and at the most prominent part of the convexity of the lens, either on the anterior or posterior aspect, and capsular where the change is affecting the anterior capsule or its epithelium rather than the lens substance. In animals cataract is usually of the diffuse type, going on to complete maturity, although in the horse the most important type is the incipient or partial speck-like cataract, because of its difficulty of detection. Such a speck-like opacity is always a serious defect, because, although it may remain quiescent for years, it may progress and eventu ally produce blindness, and it must therefore be considered an unsoundness when a horse is being examined prior to purchase. It is espe cially important in stallions or brood mares.
Secondary cataracts are commonly seen as a result of periodic ophthalmia (q.v.) of the horse, or severe iritis, cyclitis, or choroiditis in any animal. Traumatic cataracts follow any per forating injury which opens the capsule of the lens and admits the aqueous humour into the lens substance. The entrance of sharp instru ments or foreign bodies through a wound of the cornea is very liable to cause traumatic cataract. Sometimes a blow on the eye without perforation may produce cataract by contusion and rupture of the lens capsule. A perforating ulcer of the cornea is a not uncommon cause of anterior polar or capsular cataract.
After a wound of the lens capsule the adjacent lens substance becomes opaque and then swells up into a woolly or fluffy-looking mass, and this change gradually extends to the whole lens. Along with this, there is gradual solution and absorption of the degenerated material by the aqueous humour, until in a few weeks the whole lens will be removed and the pupil will again appear black and clear. Sight can now be restored by providing a suitable convex lens in front of the eye. On the other hand, the injury may have resulted in infection of the eye as well as mere wounding of the lens capsule. Iritis may have been set up, or even panoph thalmitis with complete destruction of the eye and incurable blindness.
Treatment. The successful treatment of cata ract is only by operation. In the early stages of the disease some have claimed to get improve ment by the use of potassium iodide, but most practitioners will agree that it is of little or no value. Various operations are in use depending on the age of the animal and the condition of the cataract. In all cases there are certain pre liminary points to be settled before proceeding with the operation. First, it is advisable to determine in the early stages of the cataract, before the lens becomes completely clouded, the normal condition of the fundus by ophthal moscopic examination, and of the retina by the reaction of the iris to light stimulus. Then, when the cataract is mature and ready for operation, it is all-important to ensure a healthy condition of the conjunctiva before undertaking any operation. There should be complete free dom from conjunctivitis or blepharitis, or any condition likely to lead to infection of the wound. The eye should then be prepared for operation. The eyelashes should be cut short, the conjunc provided the fundus of the eye is normal, an animal blind from cataract may be expected to see sufficiently well to avoid collision with objects in his path.
The time of the operation is decided in accord ance with the condition of the cataract. If this is immature, then the unripe cortical por tions are likely to be left behind when the attempt is made to remove the lens. When mature, the lens can be extracted entire without difficulty. If the cataract is allowed to go on to the stage of hypermaturity the cortical sub stance may either become fluid or it may dry up and harden, whilst the capsule is likely to become thickened. In neither case is it so favourable for operation.
Discission, or the needling operation, is one of the simplest procedures. It consists in scratching and opening the anterior capsule of tival sac thoroughly irrigated with normal saline or sterile boracic acid solution, and the eyelids painted with tincture of iodine. The question of whether general or local, has then to be determined, and finally the par ticular operation has to be decided on.
Operations for Cataract. In partial cataracts which present at the pupillary area an iridec tomy (q.v.) may afford some degree of sight, but it is of very doubtful value in the horse because of the limitation of the eye movements in that animal. In the dog the operation may give quite useful results. In the case of a diffuse cataract it has to be considered whether any appreciable improvement of sight will be afforded by the removal of the lens. In animals it is obviously impracticable to bring about restoration of sight by the habitual use of glasses. On the other hand, an animal totally blind from cataract will be benefited even by the very imperfect vision afforded by the opera tion alone. After the removal of the lens, 1 for Eye Operations,"p. 743.
the lens so as to allow the aqueous humour to infiltrate the lens substance, so bringing about the breakdown, solution, and absorption of the lens fibres. The cataract should be mature before the operation is undertaken, as the dis integration process then occupies a shorter time. Similarly, the larger the opening in the capsule the shorter the time for solution and absorp tion of the lens. Only a moderate opening should be made at the first operation, but it may, if necessary, be repeated.
The animal is anaesthetized, a speculum applied, and the eye fixed with fixation forceps. The needle is entered under the conjunctiva a few millimetres outside the corneo-scleral margin, then at the margin turned into the anterior chamber. The point of the needle passes across the chamber to the lower edge of the pupil, then is inserted into the lens capsule, and a vertical incision is made in the capsule. The needle is then withdrawn and a little. aqueous humour escapes with it. To prevent any prolapse of the iris atropine is to be in stilled before the operation, and its use continued until absorption is complete.
Discission answers best in young animals, when the lens nucleus is not too hard, and the tend ency to iritis not serious. Strict asepsis is essential to success. In some cases increased intraocular tension has been observed following the operation, owing to swelling of the lens blocking the canal of Schlemm. Iritis may occur because of the irritation due to particles of the disintegrating lens.
Extraction of the Lens. Several operations have been devised for the extraction of the cataractous lens, and each has some special advantage under differing circumstances. Only one operation will be described here, and readers desiring detailed information of the other methods available are advised to consult works on diseases of the eye in human surgery.
knife is being withdrawn. The capsule may be incised by means of a cystotome or capsule knife, or torn by means of special forceps.
Major Henry Smith, of the Indian Medical Service, practises and advocates a method of extraction of the lens in its capsule, This, when successfully accomplished, is undoubtedly the ideal method of extraction, but there is very considerable danger, during the manipulation necessary to press out the lens, of prolapse of the vitreous. The cystotome is introduced through the corneal incision, across the anterior chamber to the lower edge of the pupil, and then is turned with its edge towards the capsule, and two incisions, one up and outwards, one up and inwards, like the arms of a V, are made in the capsule. A transverse incision is then made joining the former two at the top.
The lens is now made to present at the corneal The operation here described consists of the following stages: corneal incision, incision of the capsule, presentment and removal of the lens, and the toilet of the part. A further step, that of iridectomy, may in some cases be prac tised with advantage prior to the incision of the capsule. After anaesthesia has been secured, the conjunctiva disinfected, and speculum and fixation forceps applied, the corneal incision is made in a similar manner as that for iridectomy, either with or without a conjunctival flap. Using a Graefe's cataract knife, the point should be inserted just outside the corneo-scleral margin, the knife made to traverse the anterior chamber and make its exit at the corresponding point on the opposite side of the cornea—the entrance and exit being at such a level as to leave about one-third of the cornea above the line joining them. An upward incision is then made so as to leave a flap of cornea. Cutting through the corneal substance, the blade is seen to lie subjacent to the bulbar conjunctiva, and the incision can be continued so as to leave a con junctival flap. Aqueous humour escapes as the incision by pressure being applied with a spatula just below the lower edge of the cornea. When the upper end of the lens tilts forwards into the incision the spatula is gradually moved up over the cornea and the lens gently pressed out, The extraction at this stage can be assisted by the use of a spoon or forceps to grasp the lens as it escapes through the wound. Great care must be taken to avoid rupture of the suspen sory ligament, or prolapse of the vitreous, or prolapse of the iris.
The last stage consists in seeing that the pupil is clear, and that particles of the cortex have not been left behind; in seeing that there is no prolapsed iris in the wound; and that blood-clots are removed and the flap evenly laid down. The conjunctiva is then flushed with normal saline solution, and the dressing of sterilized lint and gauze is fixed with a lightly applied bandage. The eye should not be dressed again for forty-eight hours, and then only gently irrigated, after which a drop of atropine solution is instilled and the dressing reapplied.
Iridectomy before incising the capsule has for its object the prevention of prolapse of the iris. This prolapse is not so likely to occur during the operation as at some time during the first two or three days, before the corneal incision has healed. The aqueous humour within a few hours of the operation may have been replaced, and with some sudden effort on the part of the patient, such as a cough, the pressure is then enough to force aqueous humour out through the corneal wound, carrying with it a portion of the iris. An iridectomy with only the narrowest coloboma is sufficient to prevent this prolapse, and it is an advisable part of the cataract operation.
Dislocation of the lens may be a congenital defect, or it may result from injury such as a blow on the eye, or as a consequence of a per forating wound of the cornea and escape of the aqueous humour and prolapse of the lens. The dislocation may be partial or complete, and it may take place into the anterior chamber or into the vitreous. With either partial or com plete dislocation the refractive power of the eye is quite abnormal.
Treatment. Complete dislocation into the anterior chamber usually calls for operative extraction because of the irritation set up.
Dislocation of the cataractous lens due to hypermaturity is not uncommon. The chalky mass acts as an irritant if in the anterior chamber and requires removal. Sometimes the cataract is very friable and disintegrates readily when the extraction is attempted. Forceps or a spoon may have to be used after the cornea has been incised, and all remaining particles should be flushed out by means of an irrigation of warm normal saline into the anterior chamber.
XII. Diseases of the Retina and Optic Nerve Retinitis is a very rare disease in the domesticated animals, and this is not surprising when it is understood that disease of the retina in man is almost always due to constitutional or general disease rather than to any local abnormality in the eye. The' main causes of retinitis in man are syphilis, which does not occur in animals; nephritis with albuminuria, diabetes, and leuccemia, none of which are common in animals. Cases have been recorded in horses following influenza and contagious pneumonia, but they are very rare.
In all these cases the retinitis usually affects both eyes. The chief signs on ophthalmoscopic examination of the fundus are a general cloudiness of the retina, marked congestion of the vessels, and a blurring of the outline of the optic disc. After a time there is exudation and often haemorrhage from the congested vessels.
Treatment. There is no satisfactory treat ment for retinitis. If a general systemic disease is responsible, treatment of the underlying cause may relieve the eye disease.
Retinal Haemorrhage is a condition not uncommon in man because of the liability of man to disease of the arteries. It is, however, a very rare thing to find arterial disease in the lower animals, and retinal haemorrhages are equally rare.
Tumours of the Retina See"Tumours of the Eye,"p. 774.
Diseases of the Optic Nerve Optic Neuritis. — Inflammation of the optic nerve is a very uncommon disease in animals. In man it is usually caused by some disease of the brain, especially a brain tumour. Other causes are cerebral abscess, meningitis, especially the tubercular type, sometimes subdural haemorrhage or fracture of the skull.
In all these cases there is an increase of intracranial pressure, and this, acting on the optic nerve fibres coming through the lamina cribrosa at the back of the eye, leads to venous congestion, and oedema in the nerve. Subse quently there is formation of a new connective tissue and consequent atrophy of the nerve fibres. The appearance to the ophthalmoscope in the earlier stages is that known disc being swollen or even dome shaped, the veins greatly distended and tortuous, whilst the arteries are contracted.
Other causes of optic neuritis are inflammatory processes in the orbit, such as cellulitis or. abscess. The condition may also occasionally follow the acute febrile diseases influenza and pneumonia in the horse, and distemper in the dog.
When the congestive stage goes on to Optic Atrophy from pressure of exudate and new connective tissue around the nerve fibres, the appearance of the optic disc changes. The congestion of the vessels passes off, and the disc itself becomes greyish-white in colour, and flattened. With optic atrophy blindness comes on.
Treatment. There is no useful treatment for cases of optic neuritis or atrophy except to remove the underlying cause at an early stage if it can be discovered.
Amaurosis, Ambylopia Amaurosis is the term applied to a state of blindness usually without any obvious lesion to account for it.
Amblyopia or dimness of vision is a condition which may precede amaurosis, and the causes of the two are similar.
Cases of unexplained partial or complete blindness occurring more or less suddenly and usually affecting both eyes are seen in all animals, especially horses, cattle, and dogs. The number of such cases is becoming fewer with increased knowledge of the pathology of eye diseases, and so the term amaurosis is being used less than formerly.
Symptoms. The animal shows the usual signs of defective sight, running into stationary objects, and showing the uncertain gait and hypersensitive ear movements of a blind animal. The condition may come on gradually, but more often arises suddenly or is not noticed until blindness is almost complete. On examina tion the pupil is found widely dilated, and the eye has a fixed, glassy look. The pupil does not react to light stimuli. Ophthalmoscopic examination often reveals nothing abnormal.
Causes. - Amaurosis may be toxic in origin, and this is probably the cause in the majority of cases. Certain drugs given in toxic doses affect the retina, probably by their effects on blood pressure and the blood supply of the part, and so produce temporary or sometimes per manent blindness with widely - dilated pupil. The drugs commonly responsible are quinine, filix mas, and areca nut, and the condition is especially liable to occur in the dog. Poisoning with lead will cause the same condition. In man excessive use of alcohol and tobacco may lead to a similar result.
Amaurosis may also be seen as a symptom in some cases of meningitis, also in epilepsy. A temporary amaurosis may occur after profuse hemorrhage.
The condition may occasionally be unilateral, in which case it is likely to be due to local disease of the retina or optic nerve of that side, or a brain lesion, rather than to a constitutional disease.
Treatment. If the condition is toxic in origin the first step is to stop the administration of the responsible drug. A purgative should then be given, followed by treatment with tonics as digitalis or strychnine. Inhalations of amyl nitrite often give temporary relief and may be repeated frequently.
Where alterations in the structure of the retina or optic nerve have taken place, treat ment is of no avail.
XIII. Displacements of the EyeballXiii. Displacements of the Eyeball Exophthalmos or proptosis is a condition in which the eyeball bulges more or less, and is therefore too prominent, as in certain breeds of dogs, notably pugs, Japanese and Pekinese spaniels. In other breeds the eyeball is normally prominent, and in other animals prominence of the eyeball is abnormal. The condition may result from the pressure of an orbital tumour, or an abscess, or from cellulitis or emphysema in the connective tissue in the orbit. Marked oedema of the eyeball (see"Glaucoma") may make the globe over-prominent, or hemorrhage or pus formation into the eyeball may produce the same appearance. In the dog and cat the orbital salivary gland is in contact with the periorbital structures just deep to the lower eyelid. Abscess of this gland occurs in the dog and cat and leads to marked proptosis.
Treatment. In cases of cellulitis, or abscess, fomentations must be applied, and the ordinary surgical procedure for the early evacuation of pus and general treatment of septic conditions must be followed. Glaucoma, haemorrhage, or pus formation in the eyeball necessitates special treatment, which has been described elsewhere in this chapter.
Exophthalmic goitre has been recorded in the horse, ox, and dog. The condition arises from over-secretion of the thyroid gland and is characterized by some degree of exophthalmos or proptosis, by enlargement of the thyroid gland, and tachycardia (i.e. frequent pulse). In addition to these characteristic symptoms there may be in the dog vomiting and diarrhcea with irregular appetite, and in the horse excite ment and nervousness.
Treatment. Radical treatment consists in lessening the amount of thyroid substance absorbed by partial excision of the thyroid gland.
Strabismus, a rare condition in animals. From want of co-ordination, or of balance in the pull of the orbital muscles, the eye is deflected and the visual axes of the two eyes do not meet at the object looked at.
The squint may be due to overaction of one muscle or to paralysis of the opposing muscle. The eye may be deflected outwards, i.e. divergent squint, or inwards, i.e. convergent squint, this being much the more common. Vertical or oblique deflections are much rarer. Hobday has recorded cases in the and these are not very rare. Clive Webb recorded one in a ' Causes. The condition may be due to paralysis of one or more of the ocular muscles as a result of a lesion (1) in the orbit, (2) in the brain. The lesion in the orbit may be a fracture, or a wound, or an abscess, involving either the muscle itself or the nerve supplying it. The lesion in the brain may be a neoplasm, or meningitis, or the result of an injury such as fracture of the skull, or it may be part of a systemic disease such as rabies, with paralysis of certain muscles as a characteristic symptom.
On the other hand, strabismus may be due to the overaction of one or more of the ocular muscles, generally as the result of hyper metropia or, less commonly, myopia, the patient making an attempt to correct for the difficulty in accommodation in the abnormally refracting eye.
Treatment. In the paralytic cases due to orbital disease, the treatment of this latter condition may relieve the squint. If due to a brain lesion there is no treatment likely to be of any avail. Strabismus due to over action of a muscle may be relieved or cured by either (1) dividing the overacting muscle or (2) advancing the point of insertion of the less active muscle so as to shorten it.
The eye is anaesthetized by an instillation of cocaine and by an injection of a few minims of a 1 per cent solution under the conjunctiva just over the insertion of the muscle to be divided. The speculum is inserted, fixation forceps applied, and an incision made in the conjunctiva over the insertion of the muscle with scissors. Probe-pointed scissors are in serted into this incision and the subconjunctival connective tissue divided so as to free a passage for the strabismus hook to beyond the insertion of the muscle. The hook is passed under the muscle and drawn forward close up to its in - sertion into the sclerotic. One blade of the scissors is now passed in between the hook and the globe and the tendon is divided. It is important to see that all the width of the tendon has been divided, otherwise the operation will probably be unsatisfactory.
Nystagmus is a condition in which there is an oscillatory motion of the eyeball when the animal attempts to look at an object. The condition prevents the eyeball coming to rest at once when it is turned on to an object. Instead it moves rapidly to and fro several times before settling down. The movement is quite involuntary and is usually in the horizontal direction. It is due in the majority of cases to cerebellar or vestibular disease, with consequent incoordination of the ocular muscles; or to hysteria, eclampsia, and such conditions. It is also seen commonly in cases of albinism, and this again is associated with errors in refraction.
There is no treatment to be advised for nystagmus.
Dislocation of the Eye.Dislocation or pro lapse of the globe occurs generally as the result of trauma. It is said to be produced some times as the result of pressure from growing tumours in the orbit behind the eye. In car nivora, particularly in dogs of the pug, bull dog, and Pekinese and Japanese spaniel breeds, comparatively slight injuries can dislodge the globe anteriorly from the orbit. The incom pleteness of the bony orbit in carnivore no doubt lends itself to the occurrence of the accident.
In the horse dislocation is rare, except as a result of fracture of the orbit.
The condition is a distressing one, as much pain and damage to the delicate structures of the eye accompany the prolapse. The lids are usually found fixed behind the globe, with marked congestion of the exposed conjunctiva and often tearing of muscle fibres. The appearance of the globe will depend upon the length of time since the prolapse occurred. The cornea soon becomes dry and opaque, and a great increase of intraocular tension is probably present in all cases, on account of the strangulation pro duced by the tight lid margins. If the dis location is of more than a few hours' duration the congestion and cedema may be such as to render reduction impossible. Further, the effects of the strangulation are often so serious as to render the eye useless, even if the attempts at reduction are successful.
Treatment. The sooner attempts at reduction are commenced after dislocation the greater the chance of easy reduction and restoration of normal sight. The animal should be put under morphine, the eye cleansed by irrigation with normal saline or by means of wet swabs, and then lubricated with sterile glycerine. A large piece of gauze folded several times is then wrung out of saline solution and used to envelope the eye so as to obtain equal pressure from all sides. The congestion may often be greatly reduced by fomenting the eyeball with sterile water containing ice for a quarter of an hour before attempting the reduction.
It may be necessary to enlarge the palpebral fissure by snicking the rim of the orbicularis at the outer canthus, and some surgeons recommend puncture of the anterior chamber to relieve the tension, but the advantage in most cases is doubtful. To prevent recurrence while the parts are stretched, the lids may be sutured together, or else closed by adhesive strapping, while hot packs may be applied to the eye for the relief of pain. It has been our experience, in most cases where prolapse has occurred more than a few hours before replacement, that the sight is permanently impaired if not lost.
Anophthalmos. True anophthalmos, i.e. com plete absence of any representative eye structure, is unknown. The name is usually applied to that form not uncommonly found in foals and puppies where no fully-developed eyes are present. It may be unilateral or bilateral. The palpebral aperture and the orbit are small, and the globe of the eye is represented by a small pigmented cyst to which are attached the rudimentary ocular muscles.
Microphthalmos is a condition in which the eye is small, the ocular cleft having failed to fuse during development. A cyst is usually present, which may occasionally develop into a large cystic mass if the animal is allowed to survive.
Treatment. Anophthalmos and microphthal mos are not capable of treatment, but a condi tion in which there is an eye smaller than normal but still capable of sight is not uncommon in puppies. Often the membrana nictitans over laps the small globe and protrudes somewhat. The prominent membrana should be removed, and any opacity of the cornea which it may have caused should be treated.
Cyclops. Fusion of the orbits gives rise to a condition known as Cyclops, usually only seen in festal monsters. A cyclops horse not other wise deformed has, however, been known to reach maturity.
Ankyloblepharon, or fusion of the lids, rarely occurs as a congenital condition. In dogs and cats a temporary state of fusion exists for the first few days after birth. In cases where the union persists, the lids should be divided along the palpebral margin, care being taken to pre vent reunion by stitching the conjunctiva to the lids at the line of incision and anointing the parts with vaseline.
Blepharophimosis is the term applied to a small palpebral aperture which occurs as a con genital deformity. It is not infrequently seen in puppies (see"Entropion").
Treatment consists, as stated, in performing a canthoplastic operation.
Congenital opacity of the cornea is occasion ally seen in the form of whitish areas tending to clear up spontaneously. Other congenital abnormalities are persistent papillary membrane, congenital cataract, and dislocation of the lens, but they are rare and unimportant.
XIV. Tumours of the Eye and its Appendages.
In describing the tumours affecting the eyes of animals and their treatment it is convenient to group them together rather than discuss them under the diseases of each separate struc ture. In animals the commonest tumours are those of the eyelids, including the membrana nictitans, of the conjunetiva, the carunele, and the glands within the orbit. The skin covering the eyelids is not uncommonly the starting point of papilloma in the horse, and fibroma, or even the malignant epithelioma and sarcoma, may originate there. Such, however, are not eye tumours proper and only affect or invade the eye secondarily. When they are seen, how ever, their possible effects on the eye should be borne in mind with a view to their removal if necessary before such effects are produced.
The conjunctiva, palpebral or bulbar, may be the point of origin of a number of benign tumours. A fibroma may sometimes be seen growing from the palpebral conjunctiva, and so coming to lie between the eyeball and the lid. Because of this position the tumour is usually flattened and may be pedunculated. By press ure and local irritation of the cornea it may cause opacity, and also produce deformity of the eyelid. The treatment of this growth is early excision.
Another rather rare tumour of the conjunctiva is a lipoma, occurring as a lobulated mass of fat between the ocular muscles, subjacent to the conjunctiva. This is a congenital tumour, and may require to be removed if by increasing growth it causes pressure on the eyeball and strabismus or exophthalmos.
Dermoid.Commoner than the above is the growth known as dermoid (Fig. 183). This is often congenital, and it is found as a small, smooth, fleshy-looking, flattened mass generally growing from the conjunctiva at the corneo scleral margin. In structure it is more or less like the normal skin, with the same complex histology. Thus it consists of dense vascular connective tissue containing glands, fat, and sometimes muscle fibres, and covered with stratified epithelium. From its surface in many cases grow more or less numerous hairs (Fig. 183), and the surface epithelium does not undergo any horny change, but the cells remain soft and swollen due to the constant action of the lachrymal secretion. Dermoids are most commonly seen in the dog, but also not infre quently in the ox.
Symptoms. The growth is a continuous source of irritation, and so causes lachrymation and increased annoyance by flies. It may show a tendency to spread over the cornea and so interfere with vision.
Treatment. The tumour should be removed by careful dissection from off the cornea and sclera after the instillation of cocaine and adrenalin.
Two other outgrowths from the conjunctiva may be mentioned here, viz. pinguecula and pterygium.
False pterygium, or pseudo-pterygium, is the name given to a strand of conjunctiva which is sometimes seen stretching across from the bulbar conjunctiva outside the limbus to the middle of the cornea after the healing of a corneal ulcer. This is simply due to the adhesion of a loose bit of conjunctiva to the corneal wound. and a corneal leucoma forms at the point of attachment. That the neck of the strand is unattached can be shown by passing a probe through behind it. The growth is best removed by applying two ligatures—one round the base and one round the apex. The leucoma may afterwards be lessened in extent and thickness by the use of the silver nitrate stick.
More important and commoner than these benign tumours are various forms of malignant growth.
When the membrana is the seat of origin, the excision is easy, and if done when the growth is quite small is likely to be followed by a radical cure. Where other structures in the eyeball are involved, the whole globe with the membrana should be removed. When the lachrymal ducts and sac, and sometimes the lachrymal bone, are invaded, an extensive and difficult operation is called for, and recurrence of the growth is almost certain. Usually in these advanced cases the animal has to be destroyed.
Sarcoma rarely arises from the conjunctiva, although pigmented, small, round-celled, or more rarely spindle-celled, sarcoma are occasionally seen beginning at the corneo-scleral margin, or down in the f ornix. Such growths are rounded, black or brown in colour, sometimes lobulated, and very vascular. They do not ulcerate as a rule, although they may break down as a result of interstitial haemorrhage and degeneration. Usually they are smooth, shiny, and covered by an epithelial layer.
Sarcoma of the orbit, whether of the bone or neighbouring connective tissue layers, is much commoner, but may lead to marked displace ment of the eyeball, causing proptosis, exoph thalmos, and ultimate destruction of the eye.
Sarcoma originating in the choroid is the commonest intraocular tumour. It may be of the pigmented (melano- sarcoma) or non-pig mented type. As the growth increases intra ocular tension rises, the vitreous often becomes opaque, and soon either cornea or sclerotic is invaded and perforated, revealing an irregular greyish mass. The tumour by now fills the orbital cavity so that the eyelids are tightly stretched over the globe. It usually breaks down at one or more points because of haemo rrhage into its substance, and discharges an offensive sanious matter. The skin of the eye lids and the bones of the orbit are often invaded, and secondary growths occur in other organs, as the liver or lungs.
The diagnosis of choroidal sarcoma is difficult, but since blindness is caused at a fairly early stage, and the globe is becoming increasingly tense and too large for the eyelids to close over it, extraction of the eye is indicated. If this is done promptly, the progress of the disease may be stopped before secondary deposits have occurred.
Melanosis Oculi.The iris or other parts of the eye, conjunctiva, sclera, or choroid may sometimes contain areas of deep pigmentation like pigmented moles of the skin. Such may be the starting-point of malignant new growths of the melanotic sarcomatous type.
Endothelioma is another tumour, of a low type of malignancy in most cases, which may be found in connection with the eye or orbital cavity. It is often encapsuled and slow-growing, showing little tendency to recur after excision. A case, apparently of this type, is recorded by On the other hand, cases occur in which an / endothelioma shows rapid growth, an infiltrat ing habit, and all the signs of malignancy. In one such case seen by the writer in a horse there was a large fungating mass originating ap parently from the conjunctiva or the membrana. The growth caused eversion of the upper eyelid and atrophy of the eyeball. Because of this possibility the general rule of early excision of the membrana or of the eyeball from which the growth commences should be observed.
Glioma is a rare tumour which originates in the retina. It occurs in the human subject, and no record of a case in animals has come under notice. The growth pushes forward the retina, and then invades the eye. The neighbouring glands may be involved and secondary growths are sometimes found in the liver.
Intracranial Tumours.Although unrelated to tumours of the eye and its appendages, it is of interest to mention the effects of intracranial tumours on the eye. Any tumour growing inside the cranium necessarily causes an increase of intracranial pressure. The lamina cribrosa, i.e. the perforated plate of the meninges through which the optic nerve makes its exit from the skull into the orbit, is one of the weak places in the cranial wall, and one effect of increased pressure is to cause a bulging of this membrane and pressure on the optic nerve-fibres coming through it. The result is that in a large per centage of intracranial tumours, whether of the brain, meninges, or bones, there is interference with vision. Especially is this the case with tumours of the cerebellum. The characteristic sign, visible only by means of the ophthalmo scope, is that known as"choked disc"in which the disc is greatly swollen and prominent, the veins in it being distended from back pressure, whilst the arteries are compressed. If the animal lives more than a very short time, complete optic atrophy and blindness result.
XV. Parasitic Affections of the Eye The parasitic diseases of the eye are few in number. The skin of the eyelids may be affected with skin parasites as in the various forms of mange, infection with lice, ticks, and flies. Similarly the parasitic fungi causing ring worm very frequently attack the skin about the eyelids. These various parasitic conditions of the skin do not concern the eye proper except in so far as they set up irritation, and so lead to rubbing and scratching of the eyelids. By this means damage may be done to the eyelids, causing distortion or scarring, and so entropion or ectropion may be produced. Or the con junctiva may be infected and conjunctivitis set up; or the cornea may be abraded or wounded, with serious results to the eye. For this reason the treatment of parasitic disease of the skin about the eyelids is a matter of concern to the ophthalmic surgeon. These parasitic diseases have to be distinguished from eczema of the eyelids, which also is important because of the irritation it sets up and the damage it may cause.
There are other parasites which occasionally find a locus in the eyes of animals, such as Hamopis sanguisuga, the leech; and possibly the larve of Hypoderma. Again, the parasites which involve muscles such as Trichinella spiralis, sarcosporidia, and various Cysticerci may occa sionally invade the ocular muscles. All these are rare—Cysticercus cellulosce, the pig measle, being the one most often recorded. In the human subject cysticerci have been recorded fairly often subjacent to the retina and some times subjunctival, and one or two cases of this aberrant parasite have been recorded in animals.
There are, however, a number of parasites belonging to the nematode worms and of the family Filariidae which affect the eye, inhabiting either the conjunctival sac, so setting up verminous conjunctivitis, or invading the globe of the eye, so producing more or less diffuse ophthalmia.
Verminous conjunctivitis or extraocular filar iasis is most commonly seen in the horse and ox, more particularly in the latter, in which animal the condition is described as fairly common in the south of France. A similar condition has been described by Dale as occur ring in the dog in the Punjab (due to Kelazia collipadia); by Lees in the camel in India (due to Kelazia Leesi); and by Cobbold and other writers in the fowl in China (due to Filaria Mansoni). The condition in animals other than the horse and ox is a somewhat rare one, and differs little from that described for the horse and ox.
In the horse verminous conjunctivitis is a rare disease, and even when parasites are present, either beneath the eyelids in the conjunctival sac or in the lachrymal canals, symptoms may be so slight that the condition is un suspected until it is specially looked for. In some cases, however, there is marked conjuncti vitis, with epiphora, photophobia and tenderness, and these may be followed by keratitis and permanent opacity of the cornea. The causal parasite is Kelazia lachrymalis (vel. Islam lachrymalis vel. F. palpebrali8), the male being 8-12 mm. and the female 14-18 ram. long. Usually only two or three worms are found under the lids, but sometimes a large number. The same parasite may invade the anterior chamber of the eye, setting up ophthalmia. The mode of infection is unknown.
In the ox the condition is more common than in the horse, and it is especially prevalent in the south of France and in Belgium. Epidemics of the disease have been recorded in France, occurring in the late summer and autumn. Three species of parasites have been implicated: Kelazia Rhodesi, T. gulosa, and T. alfortensis. As in the horse, so in cattle, the parasites are usually confined to the conjunctival sac, often under the membrana nictitans, but they may invade the anterior chamber of the eye. The symptoms are the same as in the horse, and from conjunctivitis there may be extension to the cornea with the possibility of ulceration.
Treatment consists primarily in the removal of the worms, using a soft camel-hair brush. It is necessary afterwards to irrigate the con junctival sac thoroughly to remove any debris of worms or ova, and also the products of inflammation, with 1 in 2000 sublimate solu tion, or silver nitrate 1 to 2 grains to 1 ounce of water. For further treatment of the con junctivitis and any complications see"Con junctivitis,"p. 755.
Treatment. - If Been in the early stages, before much thickening or growth of granulomatous tissue has occurred, the use of silver nitrate solution to promote an acute inflammatory reaction is probably all that is required. If overgrowth of tissue has occurred, its removal may be necessary by operation.
Verminous Ophthalmia, Intraocular Filar iasis,"Worm in the Eye."—This condition is seen in both horses and cattle, much the more commonly in the former.
In the horse the disease occurs fairly fre quently in India, from Ceylon to Burma, and it has been described by several writers, notably Lingard? Cases in Europe and America are now rare, although epidemics have been recorded in France and Belgium. The causal parasite has been variously named. Rivolta considered it an immature form of Filaria equina or papil lo8a, whose common habitat is the peritoneal cavity. Cobbold adopted the same view. This is probably incorrect, and the fact that F. equina may be found not uncommonly in the peritoneum of horses in various parts of the world where ocular filariasis is unknown is evidence against this view. Thus the question as to whether Filaria oculi, as the parasite is most commonly named, is a distinct species must be considered still undetermined. The worm is thread-like and generally white or sometimes pigmented, with an average length of 24 mm. (Lingard) and a width of about 300 mm.
Symptoms. These are due to the worm acting as a foreign body. There is lachryma tion, twitching of the eyelids, photophobia, and conjunctivitis in the early stages. Then the iris becomes inflamed, the aqueous humour tends to become turbid, and the cornea opaque. The opacity is diffuse and at first thin and nebulous, but shortly the cornea becomes thickened and a streaky dense opacity results. With movements of the parasite from the front to the back of the iris an early corneal opacity may clear up, but only temporarily.
Mode of Infection. This is not definitely known. It is possible that the ova of the parasites may have been introduced by flies, or through the agency of water, or from hay, lucerne, dry grass, or other food materials. Animals from Australia, where the condition is unknown, introduced into those parts of India where the disease is most prevalent, have been found affected commonly within twelve months of their arrival in the country.
Treatment must be undertaken as soon as the condition is diagnosed, since operation is much easier whilst the cornea is still trans parent. The eye is thoroughly irrigated with boracic acid solution or sterile saline solution, and then anaesthetized with a solution of cocaine, atropine, and adrenalin. The horse may be operated on whilst standing, or pre ferably when cast. A speculum is used to keep the lids open, fixation forceps applied, and an incision made through the cornea in the lower and outer quadrant close to the corneo-scleral margin with a small lancet. The aqueous humour escapes and carries out the worm with it, so that it can be seized with forceps. A further irrigation of the eye with boracic acid or saline solution and the application of a cold compress completes the operation.
The only further treatment is addressed to the removal of the corneal opacity and relief of the conjunctivitis, if any.
XVI. Diseases of the Orbit The bony socket and its contents outside the globe of the eye may be involved in various diseased conditions which will have a more or less direct effect on the eye.
Injuries of the bony rim of the orbit and fractures involving its walls may affect the various nerves coming through the foramina. With compound fractures infection of the soft tissues is likely to occur, and cellulitis or abscess formation or emphysema may result. Blows on the eye may cause marked contusion of the structures in the orbit, with effusion of blood and sometimes suppuration later.
Treatment consists in relieving the distress of the animal by the application of fomentation or some of the forms of kaolin paste, while pus should be at once evacuated when formed. It should not be forgotten that a direct infection of the cavernous venous sinus, with septic meningitis and pymmia, may result from a spread of pyogenic organisms along the ophthalmic veins.
Tumours. The primary malignant tumours of the orbit may be sarcoma and endothelioma, but neither is very common. Secondary in vasion of the orbital structures may occur due to epithelioma, commencing in many cases m the membrana Benign tumours of the orbit may occur occasionally, as fibromata and dermoids.
The treatment in all cases is removal of the growth as early as possible.