126 CANINE MEDICINE AND SURGERY 



delay with a Graefe's knife after the manner of 

 Soemisch. This method consists in introducing the 

 knife in the sound 'corneal tissue on one side of the 

 abscess, the back of the instrument being held to- 

 ward the center of the eye and its edge turned for- 

 ward. Maintaining this position, the abscess is bi- 

 sected by bringing the knife out on the opposite side 

 of the cornea, the cut being made horizontally. By 

 this method the ulcerative process is checked and 

 any pus in the anterior chamber evacuated. It must 

 be remembered that opening the anterior chamber 

 is an essential part of the operation, and responsible 

 for its success. 



Opacities of the Cornea 



Corneal opacities are sometimes congenital, but 

 generally they are the result of inflammation, injury, 

 or ulceration. According as they present a slight haze, 

 a defined spot, or a dense and permanent opacity, 

 they are termed nebulae, maculae, or leukomata. As 

 the tissue of the cornea is resistant and inelastic, 

 any loss of substance is made up by exudation and 

 subsequent organization of connective tissue and 

 epithelium; consequently the opacity is as large as 

 the original loss of substance. Vision is afifected 

 not only according to their extent, density, and posi- 

 tion, but by reason of the alteration which thpy 

 cause in the corneal curvature. 



It is remarkable what great reparative powers 

 the corneal tissues have and to what extent the 

 effused lymph will clear. Consequently in growing 

 animals, with perhaps the exception of the scar left 

 by an abscess or deep ulceration, the prognosis of 

 good eyesight with any small opaque scar is good. 

 With older animals, however, owing to their low 

 power of recuperation the prognosis is the reverse. 



