CORNEA, DISORDERS OF THE (see also KERATITIS).—Most injuries of the cornea are of importance chiefly on ac count of the accompanying injury of deeper structures, such as the iris and crystalline lens, or because of the lodg ment of foreign bodies, or through infec tion giving rise to keratitis, or more ex tended inflammation of the eye.
Burns.— Injuries frequently cause corneal ulcer (see below). Ultimately it may lead to corneal opacity or irregular astigmatism (see ASTIGMATISM). The same is true of burns, either by heat, acids, or caustics. A burn by heat or by nitric acid may cause a super ficial coagulation of the corneal tissue, giving an impression of complete opacity of the membrane, but upon the separa tion of the injured tissue, which may occur in a few hours or at most a few days, the cornea is found to be clear and comparatively uninjured. Burns by lime are frequent, and very serious in their effects, the lime forming a union with the tissue, which makes it difficult to remove, and continuing-, therefore, to act as a caustic for a considerable length of time.
Treatment. —Simple burns by steam or I hot metal after removal of the metal I should be treated by keeping the eyes closed under a light bandage and ing twice a day with boric-acid solution.
Injury by quicklime may be met by the filling of the eye with olive-oil; and especially requires the earliest possible removal of all the retained caustic. Other caustic alkalies may be neutralized by very dilute acids, as vinegar and water; but reliance should be mainly placed. on washing with water or solution of boric acid.
Acids may be neutralized by lime water, or solutions of sodium or potas sium bicarbonate, or soap-suds. But the best means is by free washing of the con junctiva with a 1-per-cent. solution of sodium bichlorate.
Foreign bodies are so frequently im bedded in the cornea because the cornea occupies nearly two-thirds of the space between the opened eyelids, and a much larger proportion of that space when the eyes are partly closed, as they are when the entrance of a foreign body is antici pated. Again, the tissue of the cornea is of such consistence as to retain such particles as may penetrate it, whereas the conjunctiva and subconjunctival tis sue are so loose that foreign bodies im bedded in them easily work out.
When a foreign body is imbedded in the cornea it commonly causes irritation and suppurative inflammation, by which it becomes loosened and easily drops out, or is wiped away by the lids. If, how ever, it lie at the bottom of a consider able loss of substance it may lie there for some time, although quite detached from the corneal tissue. Under these circumstances it becomes a source of ir ritation, causing chronic weakness of the eye, photophobia, and excessive lacry mation, and the development of vessels in the adjoining part of the pericorneal space, which push out to the seat of the foreign body, giving an appearance of a chronic phlyctenular ulcer or superficial vascular keratitis.
Among 200 eases of foreign body in the cornea 180 presented themselves for its removal within 1 week, 11 in the second week, 7 in the third week, and but 2 after more than 3 weeks. Ten cases are reported of foreign bodies re tained in the cornea from 3 weeks to 1S months, and a few instances referred to in literature in which they have been retained even longer. Edward Jackson (Brit. Med. Jour., Jan. 8, '98).
Cases in which the laborers eniployed to knock down chestnuts have been struck in the eye by the falling chestnuts and the little spines remained in the cor nea, their bases, as a rule, being flush with its surface. For locating these bodies, Zehender's binocular lens, made by Western, of Rostock, are of great service, and the illumination should con sist of convergent rays concentrated by a large convex lens. The prickles are difficult to seize even with the finest for ceps; Bowman's needle entered obliquely is useful. It is better to withdraw those which do not penetrate the cornea into anterior chamber before those which do. To disinfect the path of the prickle after removal, a fine tattooing needle may be rotated in the wound like a gimlet, thus scraping it, while the groove of the needle allows the antiseptic to find its way down into the wound. The gal vanocautery inay also be called for. Deschamps (Ann. dDeul., Apr., '99).