160 CHAPTER V. DISEASES OF THE EYE. SIMPLE INFLAMMATION. Simple inflammation of the eyes is caused by external causes in nine cases out of ten, such as a blow, chaff falling within the eye-lids, &c., and must be treated according to the cause of inflammation. If any foreign substance be the cause, it must be removed immediately; and I have found a leaden pencil the best instrument for such a purpose. If the inflammation be very severe, the facial vein should be copiously bled, and all corn removed until some symptoms of abatement are evident. It is very rare to meet with a case where the injury is more deeply seated than the cornea in simple inflammation. Great care, however, should be taken to remove the cause before ulceration of the cornea has taken place. It is difficult for one unacquainted with diseases of the eye, to distinguish between this disease and ophthalmia by whatever distinctions may be drawn. The chief difference is, that in the former disease the cornea alone is affected, while in the latter the inflammation extends to the internal parts. This disease is divided usually into two distinct classes by professional men-Specific and Purulent Ophthalmia; but, since the symptoms and treatment will be the same, I do not think any object will be gained by treating of them separately. The symptoms are marked by closing of the eyelids, distended vessels, general muddiness of the iris and cornea, with an almost total loss of transparency, as well as by profuse weeping. The treatment should consist of darkening the stable, lowering the diet, and putting a linen compress, soaked in a solution of sulphate of zinc of about the strength of one scruple to the half-pint of water, over the eyelids. The horse will assuredly go blind sooner or later, if subject to periodical attacks of this disease; therefore, copious bleedings, large doses of physic, &c., are utterly inadmissible, inasmuch as they add to the evil by incapacitating the horse for work for a lengthened period. The best way is to dispose of a horse after having recovered from one of these attacks, unless intended for double harness, when blindness will not be of much inconvenience either to the horse or his owner. In this case, however, great care must be taken to remove the exciting cause, which I take to be plethora. It is most common in coarse underbred horses of the hackney breed, probably because their circulative organs M are less perfect. Such animals generally are possessed of a distended haw and sunken eye, and should always be avoided. One eye is generally more frequently affected than the other; but when one goes the other is not long in following suit. All kinds of wild statements are put forward with reference to this disease; the existence of a wolf's tooth is considered by many as a certain cause of ophthalmia, and its removal as a certain cure of the same. Others hold that only those horses which are subject to the pressure of a collar— thus retarding the circulation of the blood-are afflicted with it! All of which goes to prove that the direct causes are frequently indiscernible in the majority of cases. Overnight the horse's eye will be as well as usual, but on the next morning it will be, without any apparent cause, closed and inflamed. I must, therefore, conclude that predisposition of the constitution is the chief cause of this disease; though, no doubt, plethora and foul stables aid and abet in the work. CATARACT. The previous disease frequently terminates in cataract or opacity of the crystalline lens. A cataract usually commences in the centre of and behind the pupil, and is marked by no symptoms of pain or uneasiness during its formation. When a primary disease, all treatment is useless and cruel, and can be attended with no good results. This diseased state of the eyes is technically termed amaurosis, and consists of loss of sight from diseased condition of the optic nerve and retina. The eye, to all appearance save the imperfect functions of the retina, is healthy and sound. It may be caused by increased or diminished sensibility of the retina. This disease very rarely attacks both eyes at the same time. It is said to be the frequent consequence of staggers and immoderate bleeding. It may be discovered by the timidity and uncertainty of the horse's action, by the fixed size of the pupil, a shrunken iris, and insensibility to the light of a candle if placed close and opposite to the eye in a darkened stable. The cause of this disease is irritability of the retina, consequent on a determination of blood to the head in some cases, and in others is the result of ophthalmia. I had a horse in my possession affected with this disease from the latter cause, which took place while riding to meet a pack of fox-hounds only six miles distant, so rapid is its progress at times. I first discovered it by his continually putting one or other of his feet into the grips and gutters alongside of the road, a thing that I never knew him do previously. He then went much as usual, until arriving at a water ditch, into the middle of which he went without an effort to save himself, and, on coming to the stable, he walked straight up against the wall, being evidently unaware of its existence. He was stone-blind from that moment, and never appeared to regain the power of sight afterwards. This horse had been subject to severe attacks of specific ophthalmia for two years previously, for which he had never been subjected to bleeding or large doses of physic. His age was six years, and he was subject to frequent attacks of plethora. In this case no treatment is of any avail; but its existence may be partially guarded against by strict attention to the digestive organs, atmosphere of the stable, regular food, and exercise. Violent exertion should be avoided where this disease is feared, but moderate riding and driving will materially aid in warding it off. |