DISEASES OF THE CORNEA 97 



knife through the healthy cornea near the margin of the 

 ulcer, pass it along horizontally in the anterior chamber, 

 and cause the point to emerge through the healthy cornea 

 near the opposite margin, cutting forward through the 

 ulcer. This can be done under local anesthesia. Atropin 

 should be used, so that the iris will not prolapse into the 

 wound. This operation at once reduces the tension if 

 there be any, and allows the escape of aqueous and pus 

 from the anterior chamber. Under slight pressure and 

 the continued use of atropin and antiseptics resolution 

 sets in more readily. 



When the pneumococcus, which is said to be the cause 

 of serpigenous ulcer, is present, the antipneumococcic 

 serum has been used with great benefit. 



Pannus. — This is an affection of the upper and ante- 

 rior layers of the cornea, characterized by an opacity of 

 these layers, filled with numerous ramifying blood-vessels. 



In mild types the affection is superficial to Bowman's 

 membrane, but in severe types this membrane is de- 

 stroyed and the cornea proper becomes invaded. It is 

 due to friction of the diseased conjunctival surface of 

 the Kd, more particularly to trachoma, and to an ex- 

 tension of the pathologic process to the layers of the 

 cornea. 



The degree and rapidity of the disease may be so 

 great as to involve the whole upper surface of the cornea, 

 even encroaching over the pupillary area, and some- 

 times covering the whole corneal surface. 

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