EFFECTS OF KADIANT ENERGY ON THE EYE. 783 



a concave mirror. The distance separating the two was equal to the 

 sum of their focal lengths so that parallel light was thrown into the 

 atropinized eye of the rabbit. Even after a second's exposure a 

 silvery white spot round to oval in shape, covered the retinal image 

 region. It was surrounded by a brownish ring. Longer exposure 

 enlarged the silvery central spot and the surrovmding rings became 

 paler and took on a silvery sheen. Microscopic section showed 

 droplets and clumping of the coagulated albumins of the retinal cells. 

 Surrounding and below these areas were exudative and then hypere- 

 mic areas. The choroidal pigment was increased and showed a 

 tendency to wander. Indeed there was so much similarity to early 

 stages of choroiditis disseminata that he was the first to consider the 

 possibility that heat and light rays may be an etiological factor in 

 the latter disease. However Aubaret ^^°°, Hess ^^°^, and Garten ^^°^ 

 have since attempted, without success, to prove this proposition. To 

 determine the influence of heat Deutschmann passed the rays through 

 a tube of clear running water 20 cm. long. The changes could be 

 produced but it always took a few minutes longer. Therefore he 

 concluded that both heat and light are active as etiological factors. 

 In none of these cases with short exposure times were outer eye troubles 

 noted. 



In 1892 Widmark*^^ repeated Czerny's and Deutschmann's work 

 with a 1200 c. p. arc light. The exposure time was 2-12 hours, usually 

 4 hours. With the 10% quinine sulphate filter to remove ultra violet 

 light he found much less retinal trouble than with the quartz glass 

 system. Also less effect through yellow bichromate filters than 

 through blue, so that he concluded that blue violet and ultra violet 

 rays were most effective. 



Herzog ^'^^ in 1903 reported that he had repeated the work of Czerny 

 and Deutschmann in 1898 and found that the circumscribed retinal 

 lesions could be effected in | second. A similar but more diffuse 

 retinal change could be produced in | to 2 hours with a 15 amp. arc 

 light whose rays were concentrated on the rabbit's eye after traveling 

 a 28 cm. tube of alum water. Further similarity in action was noted 

 in the production in two or three old rabbits of an opaque cataractous 

 condition of the lens visible to the eye as Czerny and Deutschmann 

 had noted. When the cornea was continuously irrigated with normal 

 salt solution to avoid overheating, the result was a cloudy swelling 

 of the epithelium which was less transparent than the simple des- 

 quamation that resulted without the excess of moisture. All these 

 changes, including the cataract formation already described he ascribed 

 to light transformation to heat, and not to ultra violet light. 



