XEROSIS CORNEÆ (EPITHELIALIS). DRY KERATITIS.
This is described by Mayer as following distemper in dogs. It seems to begin in the epithelial layer of the conjunctiva, which becomes dry, lustreless, spotted, opaque and fatty so that water runs over it without wetting it. It may extend deeply into the substance of the cornea and lead to the development of a scar. When scraped and examined under the microscope the scrapings are found to consist of epithelium undergoing fatty degeneration and myriads of xerosis bacilli. As the disease takes occasion to attack by reason of the debility of the system, the treatment is mainly corroborative and tonic, including the arrest of the affection on which the weakness depends. The early application of antiseptics is desirable (iodoform 1, vaseline 10; mercuric chloride 1, vaseline 3000). Warm compresses and a bandage may be tried.
WOUNDS OF THE CORNEA.
Causes: harness, whip, nail, hay, straw, stubble, thistles, spikes, twigs, pine needles, cones, burdocks, stones, gravel, glass, splinters of wood or metal, scratches, stings. Symptoms: closed lids, epiphora, sight of lesion, soon cloudy swelling, opacity. Treatment: antiseptic bandage and lotion, boric acid, sublimate, potassium permanganate, avoid lead or zinc, atropia, cocaine, with perforation, bandage, eserine, excision. For foreign body, antiseptic cotton, spud or curette.
Causes. Corneal wounds are common in working animals by reason of contact with harness, canes, whips, etc., and in the stable from contact with nails or with the hard ends of hay or straw. At pasture the cornea is injured by the ends of long stubble, the sharp points of thistles, the spikes of various thorny plants, and twigs of bushes and trees. The last named factors are especially operative in hunters and horses worked in forests. Punctures with pine needles and cones, and with burdocks, are other common causes. Stones, gravel, pieces of glass, and splinters of wood or metal, produce traumas of the cornea, and, in cats and dogs, scratches and even perforations with the claws are common. In this connection the stings of insects are not to be forgotten.
Symptoms. There is always a prompt and complete closure of the eyelids and a profuse secretion of tears. Then on parting the eyelids with finger and thumb, the lesion of the cornea, its nature and extent should be recognizable. In case of a small, punctured wound, however, as with a smooth thorn or other conical body, the normal elasticity of the corneal tissue may lead to such a perfect coaptation of the divided edges that the lesion may escape even a close scrutiny. If the case is seen early, before time has been allowed for cloudy swelling and opacity the wound is all the more likely to escape observation. In incised, scratched and torn wounds, on the other hand, the seat and nature of the lesion are made out with the greatest ease.
Treatment of a slight wound which is at once recent and free from infection, is by a simple antiseptic bandage and lotion. Boric acid (1 ∶ 100), sublimate solution (1 ∶ 5000) or potassium permanganate solution (1 ∶ 100) may be used. Lead and even zinc salts, are liable to precipitate in the abraded tissue and cause a lasting opacity. If the pain is severe it may be moderated by the addition of atropia sulphate, or a solution of 1 to 100 water may be instilled into the eye several times daily. Cocaine makes an excellent substitute. In deeper wounds, perforating the cornea and allowing the escape of aqueous humor, there may be prolapse of the iris through the wound. It may be pressed back with a flat sterilized spatula, and retained by bandage and a course of eserine. Should it still escape, it must be seized with forceps, drawn out and snipped off with a sharp pair of sterilized scissors. The greatest care must be taken to avoid infection which may cause panophthalmitis and destruction of the entire eyeball.
FOREIGN BODIES IN THE CORNEA.
In case of penetration of the cornea by thorns, thistles, glass, metal, etc., there usually follows inflammation with a red area around the offending object. If the foreign body is a piece of iron there is a brownish area caused by iron oxide. Focal or transillumination will usually reveal the object. Should both fail, a solution of fluorescin when applied will develop a greenish area around it.
Treatment may be made as advised by Gould by pressing a little antiseptic cotton to the front of the eye, so as to entangle and withdraw the foreign body when the eyeball is rolled. Failing in this we may cocainize the eye and remove the offending object with a small curette or spud. A careful focal illumination of the eye will enable the operator to see and remove the smallest particles without injury. Subsequent treatment is that of wounds.