Part 73

COLOBOMA IRIDIS. CONGENITAL APERTURE IN IRIS.

This is a congenital defect in which there is an aperture in the iris. Hering figures the two eyes of a horse in which these appeared in the direction of the outer canthus. Renner records a case in a foal in connection with intra-bulbar enchondroma. Dochtermann and Berlin record that among 64 pigs the result of breeding a boar on his daughters and grand-daughters no less than 36 showed coloboma. Möller figures a dog with the same affection.

The condition is not known to prove hurtful to the affected animal so that it may be wisely let alone.

DOUBLE PUPIL.

Mayer notes a case of congenital double pupil in the horse, a bridge extending across the space from the upper to the lower border and cutting off the outer third of the opening. The present writer has seen a similar condition as the result of union of the corpus nigrum in severe iritis. Section of the bridge is possible, though rarely desirable, seeing that it opens a door to possible infection.

ALBINISM. WATCH EYE.

The albino is an animal in which there is a complete absence of pigment in the eye. It is usually seen in white races of rats, rabbits and dogs, and both the iris and choroid reflect a pink tint. It may cause photophobia and some weakness of vision but, in the main, it seems to be harmless to the lower animals. In horses it is occasionally seen as a partial defect, a portion only of the iris and adjacent sclerotic appearing of a brilliant white color. It does not usually seem to impair the vision, so that at the worst, it is only looked on as a blemish. It is needless to attempt a remedy.

PERSISTENT PUPILLARY MEMBRANE.

The persistence of this embryonic membrane has been noticed in the horse (Schindelka), ox (Meyer), rabbit (Mayerhausen), and dog (Möller). It tends to disappear with the growth of the animal and rarely does any perceptible harm.

OCCLUDED PUPIL.

This has been frequently found in horses as a sequel of iritis, and permanent adhesion of the contracted iris to the front of the lens capsule. It is in short, a posterior synechia with closure of the pupil. The lens and its capsule are usually opaque so that there would be no gain in detachment of the iris. If, however, there is reason to conclude that any part of the lens is still transparent, the performance of iridectomy over this portion, would produce a new aperture for the entrance of light.

CYCLITIS.

This is described by Möller as occurring in the domestic animals, but he fails to furnish instances of its diagnosis during life, and it is not likely to be often recognized in the living animal. Beside the usual signs of iritis, there is extreme tenderness to pressure around the anterior border of the sclera, increase of intraocular pressure, followed later by its diminution, and a cloudiness of the anterior portion of the vitreous humor. This last condition can only be detected by a full illumination of the vitreous, and its examination with the ophthalmoscope. It is quite liable to be complicated by suppuration and to go on to panophthalmitis.

The treatment does not materially differ from that of iritis, yet atropia must be used with caution as it is liable to increase the suffering. The preparations of mercury have been especially recommended.

CYSTS OF THE IRIS AND CORPORA NIGRA.

Mayer speaks of these lesions in horses, but it is very difficult to diagnose them correctly, even with the aid of the ophthalmoscope. The very manifest bulging at the part may be due to excess of pigment, especially in the corpora nigra, and an exploratory puncture would only be warranted when the protrusion became excessive and injurious. One such puncture by Eversbusch led to infection and loss of the eye.

TUBERCULOSIS OF THE IRIS.

This has occurred as the result of inoculation of the aqueous humor in the smaller animals, and as a spontaneous localization of the disease in cattle (Hess, Röder, Fischöder, etc.). In Hess’s case, the left eye was shrunken to half the size of the sound right eye, and small caseated tubercles were present in both iris and choroid. There are usually coincident tubercles in other organs, and these with the nodular appearance of the iris swellings, if visible in life, may assist in diagnosis. (See Symptomatic Iritis, and Tuberculosis.)

CHOROIDITIS.

Causes: as in iritis: traumatic and infective. Exudative. Suppurative. Symptoms: as in iritis: less change in iris and of flocculi in the aqueous humor; opacity of lens and vitreous. Lack lustre choroid under ophthalmoscope, uneven, detached. Suppurative form: early profuse weeping, bleeding, later suppuration, pus oozing from orifice; panophthalmitis. Treatment: as in iritis; atropia; cocaine; astringents; purgatives; diuretics.

Causes. These are largely the same as those of iritis and cyclitis. Blows, traumas, foreign bodies, sand, cinders, dust, lime, fierce light, reflection from snow, water, etc., chills, draughts, storms, irritant gases, and a number of specific diseases like influenza, contagious pneumonia, canine distemper, rheumatism, omphalitis, pyæmia, etc., may be named. It is a common lesion of recurrent ophthalmia in horses, and is not unknown in tuberculous cattle. It is usually more or less involved in iritis, as the iris is in choroiditis. The name given to the disease which involves both, will depend mainly on whether the inflammation predominates in the iris or choroid. Mayer divides it into exudative and suppurative, the latter being a common result of trauma, and likely to issue in panophthalmitis.

Symptoms. These are largely those of iritis. The congestion and redness of the sclerotic around the margin of the cornea, the fact that the enlarged vessels are firm in the sclera and not easily moved as in conjunctival congestion, and a certain partial blindness, without much change in the brilliancy of the iris, or opacity or flocculi of the aqueous humor, would suggest choroiditis. Later some opacity of the lens, or its capsule or of the vitreous humor would be equally significant.

The only certain manifestations would be such as are found on ophthalmoscopic examination. Swelling and unevenness of the inner surface of the choroid, and a loss of luster, a change of its dark surface to light colored spots and patches, (dull-red, yellowish red, grayish green) and of the tapetum lucidum to a dirty grayish green in solipeds. Areas of minute blood clot may also be seen. But these are rarely recognized or indeed skillfully sought during life, and it is mainly to necropsies that we owe most of our diagnosis of choroiditis in the lower animals.

In the suppurative form there is early profuse lachrymation more or less tinged with blood, and later oozing of pus from between the lids. The redness and swelling of the conjunctiva and lids are very prominent features, and if the lids can be separated the corneal or scleral orifice may be seen oozing pus. If visible at all the anterior chamber shows yellowish opaque contents, and the symptoms of panophthalmitis supervene.

Treatment of the exudative form is essentially the same as for iritis. Atropia lotions with or without cocaine, also astringents, which may be used warm, and generally purgatives, diuretics, local bleeding, cupping, and counter-irritants are in order. In obstinate cases ointment of the yellow iodide of mercury, and in cases of extra tension puncture of the cornea may be the means of relief. Iridectomy may be advantageous under careful antiseptic precautions. In case of extensive or general suppuration (panophthalmitis) enucleation of the eye may be the only resort, and may contribute to save the other eyeball. (See Panophthalmitis).

DETACHMENT OF THE CHOROID.

The choroid is detached from the sclera by exudates, blood effusions, or blows with blunt articles. The lesion is especially common in recurrent ophthalmia, choroiditis, and cyclitis. The ophthalmoscope will show the detached portion as a rounded elevation on the otherwise smooth concave surface, with normal or diminished intraocular tension. A tumor of the choroid is usually associated with increase of tension. After inflammation has been subdued these cases may be left to rest and time, and will often recover through absorption of the exudate. =Rupture of the choroid= from violence is to be similarly dealt with.

RECURRENT OPHTHALMIA OF SOLIPEDS. PERIODIC OPHTHALMIA. MOONBLINDNESS.