SECTION IX.. Diseases of the Eyes.

DISEASES OF THE EYES.

In domesticated animals, apart from parasitic diseases, the diseases of the eye which particularly deserve description and offer a special clinical interest are very few. These are the diseases that affect the globe of the eye or the organs annexed to it.

FOREIGN BODIES.

Foreign bodies become lodged on the internal surface of the eyelids, in the folds of the conjunctiva, in the thickness of the cornea, and sometimes, though rarely, in the anterior chamber, the lens, or the vitreous humour. They include particles of grit or dust, the awns and glumes of grain, etc.

The eyes are half closed and the conjunctiva is swollen, whilst the eye weeps and the animals dread the light.

=Diagnosis.= This is somewhat difficult, for the parts rapidly become very sensitive, and the animals violently resist examination. When the foreign body penetrates the anterior chamber or the lens, it produces suppuration or traumatic cataract.

Before anything can be done it is often necessary to render the parts anæsthetic by instilling a few drops of cocaine solution into the eye.

The foreign body may then be discovered by close observation. If the pain is very intense, and great resistance is offered to opening the eye, the practitioner may confine himself to passing a soft camel-hair brush saturated with cocaine solution over the surface of the eye and into the conjunctival sacs. The brush loosens, and often removes, the offending body. In the absence of a camel-hair brush, the little finger, covered with a piece of fine linen, may be used.

Where the parts cannot be touched owing to the resistance of the animal, lukewarm solutions of antiseptics such as boric acid may be occasionally injected into the eye by means of a syringe, but care must be taken to prevent the animal injuring itself against the syringe by sudden movements.

CONJUNCTIVITIS AND KERATITIS.

Inflammation of the conjunctiva and inflammation of the cornea almost always occur together, and reciprocally induce one another when of a certain degree of intensity. They may be simple, that is to say, produced by simple causes, or they may be specific, and of a contagious character.

Simple inflammation is caused by the action of cold, draughts, dust, or mechanical injuries. Specific inflammations, the nature of which is still little understood, occur in the ox and goat. They are very contagious, and may successively attack all the animals of a herd.

=The symptoms= of acute and specific inflammation differ very little. They comprise congestion, lachrymation, chemosis, a certain amount of suppuration, and sometimes superficial ulceration of the cornea. The patients suffer very acute pain, avoid the light, present all the symptoms of photophobia, and are affected with spasm of the orbicularis muscle.

In simple cases these symptoms frequently disappear, provided the byres are kept clean and astringent eye-washes are applied.

In contagious keratitis, however, the cornea may suppurate and even become perforated after a few weeks.

=Treatment.= The chief object of treatment under any circumstances must be to insure the most perfect cleanliness both of the globe of the eye and the conjunctival sacs.

The eye must, therefore, be irrigated with lukewarm water, the stream being injected beneath the lids. Each irrigation is followed by the use of an anodyne and astringent eye-wash containing borate of soda or sulphate of zinc, combined if necessary with cocaine.

Distilled water 100 parts. Borate of soda 4 „ Hydrochlorate of cocaine 1 „

But saturated solution of boric acid is simple, and no less effective.

In contagious keratitis the eye lotion may contain 2 to 3 per cent. of nitrate of silver, the excess of silver being neutralised by washing out with a weak solution of common salt. After three or four applications this should be changed for a saturated solution of boric acid.

VERMINOUS CONJUNCTIVITIS.

This form of conjunctivitis, described by Rodes in 1819, is due to the presence of the Filaria lachrymalis, which varies in length between ⅜ of an inch and 1 inch.

Like ophthalmia, the disease attacks cattle reared in wet localities.

=Symptoms.= The symptoms are those of acute conjunctivitis, and consist first of lachrymation, then of injection of the blood-vessels of the conjunctiva, together with swelling of the eyelids and photophobia. The animals keep the eye closed, and display extreme sensitiveness. Here again cocaine proves of value.

Examination is rather difficult, the worms being sometimes displaced towards the cornea or membrana nictitans, although more commonly they remain hidden in the folds of the mucous membrane towards the point where the membrana nictitans is inserted. It is, therefore, necessary to thoroughly expose the folds of the mucous membrane in order to discover them.

In time conjunctivitis becomes complicated with diffuse ulceration, keratitis, and sometimes with ophthalmia and suppuration of the eye.

=Diagnosis.= The diagnosis is rather troublesome, and cocaine is of great assistance.

=Prognosis.= This is rather grave.

=Treatment.= The object of treatment is the complete removal of the parasites. This can sometimes be attained by means of the finger, a pair of forceps, or a very clean feather.

Treatment is completed by injecting an antiseptic and anti-parasitic eye lotion for several days, lest some of the worms should remain hidden in the folds of the mucous membrane. One per cent. creolin or 1 in 2,000 sublimate solution may be used.

If in some exceptional case it is difficult to remove the parasites, they may be got rid of by injections or free irrigation. The stream of liquid, pointed in different directions, distends the mucous membrane and washes away the foreign bodies on its surface.

VERMINOUS OPHTHALMIA OF THE OX.

This ophthalmia is due to the presence of a small worm, ⅔ of an inch to 1¼ inches in length, which has been regarded as the larval form of the Filaria cervina of the serous cavities.

It is very common in animals which are kept permanently in low-lying meadows particularly in some parts of France, as for instance in Normandy, in the departments of the Sarthe and the Mayenne. Not infrequently it occurs as an epizootic, and is then regarded as a contagious ophthalmia. Verminous ophthalmia occurs chiefly during the spring and autumn.

=Symptoms.= The disease is accompanied by lachrymation, signs of conjunctivitis, and fear of light. Very soon the media of the eye become turbid, the sclerotic and cornea are injected, and finally exhibit marked opalescence.

On examination the eye appears extremely sensitive; in fact, it can scarcely be touched unless cocaine solution is previously applied.

The parasites, two or three as a rule, but in exceptional cases from five to seven in number, are seen rolled up within the anterior chamber of the eye. A week after the beginning of the attack, however, they begin to move about, and are then found close behind the cornea, upon the lens, or suspended in the aqueous humour.

The irritation produced sets up inflammation of Descemet’s membrane and the cornea, together with iritis, and, secondly, keratitis and changes in the lens.

Unless treatment is adopted verminous ophthalmia inevitably ends in cataract.

=Diagnosis.= Diagnosis is always uncertain on account of the difficulty of examination. When the cornea is very opaque examination necessarily gives a negative result.

=The prognosis= is grave.

=Treatment.= Eye lotions containing tincture of aloes, creolin, corrosive sublimate, etc., have been suggested, but are practically useless, because they can have no action on a parasite enclosed within the globe of the eye. The most logical treatment consists in aseptic puncture of the anterior chamber of the eye towards its lower border with a cataract needle.

The escaping liquid carries with it the parasites, and recovery is then only a matter of time, provided the wound does not become inflamed. The great danger consists in inflammation and suppuration of the eye. This, however, can be avoided by antisepsis and by applying a surgical wool dressing, which can be left in place for a few days.