DIAGNOSIS OF VARIOUS FORMS OF KERATITIS.—The diagnosis of the par ticular form of keratitis present is often very important. Here the character of the opacity or ulceration may be of great significance. Interstitial keratitis will be known by the depth of the opacity, the fine loops of the vessels, the involve ment of the iris, and the other evidences of constitutional taint. The history of a nerve-lesion or the loss of sensibility in the cornea point to neuropathic kera Wis. In the malarial form there is ob tainable a history of malaria, and the linear ulcers are in tissue having less than normal sensibility to touch. In dendritic keratitis these features are ab sent. IIerpetic keratitis is characterized by the minuteness of the scattered ulcers and the history of previous illness; and punctate by the points of chief opacity.
keratitis is known by the burn ing pain, followed by the large bleb or superficial abrasion. Pannus is readily recognized by the distribution of the ves sels and the superficial opacity; and the evidence or history of preceding con junctival disease. Traumatic and striate keratitis will give the history of injury. The suppurative ulcer will be recognized by the yellowish infiltration of the part of the cornea into which it is extending.
Etiology and domi nant facts in the pathology of corneal ulcer are that the cornea is a tissue closely related to the white, fibrous iaective tissue of other parts, that it is non-vascular, that it is peculiarly pre disposed to injury and infection, and that it is covered by epithelium liable to the same injurious influences as the epithelium of the conjunctiva. The tendency of the principle corneal tissue is shown in the controlling influence of the constitutional causes of interstitial keratitis and the prolonged stage of lution in all forms of inflammation in volving the true corneal substance.
The absence of blood-vessels is respon sible for the frequent occurrence and dis astrous extension of ulcerations, and the danger of the spread of whatever tion may occur. The extension of con
junctival infections of various kinds to the cornea is what might be expected from the similarity of their epithelial coverings.
In pathological examination of 11 eases of purulent keratitis in the human sub ject, 5 of which were examples of ulcits cornem scrpens, 4 of keratornalacia, and 2 of beginning panophthalmitis, it was found that Descernet's membrane re mained intact unless there was a com plete perforation of the cornea, although at times the endothelial cells upon the posterior surface of this membrane were absent in many places. In these cases the corneal parenchyma was found to be (edematous, the corneal spaces being en larged and filled with altered corneal cells and leucoeytes with numerous nuclei. In several instances there was a distinct exudation of fibrin between the lamelhe of the cornea, especially, however, near the ulcer. The leucocytes invaded the membrane from the limbus and mainly in the superficial layers. In the eases of keratomalacia only the lower third of the cornea showed inflammatory change. In the ordinary forms of ulceration Bow man's membrane and the corneal epi thelium were absent from about the ulcer. In the later stages of ulcus cornea ser pens the epithelial cells were greatly in creased, being absent only from near the ulcers. The authors believe that hypop yon is formed from the iris and from the surrounding spaces of Fontana and Schlernm's canal. In the eases of pan ophthalmitis the inflammation had ex tended rapidly through the retina.. Uht hoff and Axenfeld (Archly. F. Oplithal., B. 42, Ab. I).
Trophoneurotic keratitis differs in its pathology from keratilis e lagophtlialmo in that in the latter condition the lesion of the cornea is the result of exposure from an uncovered cornea, together with general loss of resistance on part of all the tissues. In trophoneurotic keratitis the lesion is found under the covered cornea. K. K. Wheelock (Ophthalmic Rec., Fcb., '98).