782 WALKER. 



injury have been reported. Essentially the same is true in blinding 

 due to short-circuit arcs, though sometimes it is difficult to distinguish 

 mechanical from light effects, as in cases reported by Grimsdale and 

 James ^^^ and by Posey ^^^ in 1911. 



The Retina: Injuries, Scotomata, Erythropsia. 



That blindness may result from direct observation of the sun of 

 eclipses, has been known without doubt for ages. Indeed Galileo ^^ 

 is known to have injured his eyes by observation of the sun with his 

 telescope. Galen ^^^ cites cases of blinding, with more or less subse- 

 quent return of vision, in observers of eclipses of the sun. He also 

 noted that central scotomata or blind spots often resulted in the 

 same way. Reid^^* in 1761 and Soemmering'*^ in 1791 according to 

 Hess ^^* probably gave the first accurate description of the subjec- 

 tive phenomena of sun blinding. 



Less frequently the same ocular disturbances have also long been 

 noted in seamen long exposed to strong reflection of the sun's rays 

 from water surfaces. Likewise travelers over desert or glary plains 

 are not uncommonly afflicted with these visual disturbances. 



Czerny ^^ as early as 1867 showed that a lesion of the retina of the 

 rabbit visible with the ophthalmoscope could be produced by the sun's 

 rays. Coccius, Ruete, in 1853, and Jaeger in 1854, had already 

 described the ophthalmoscopic changes in the human eye. Czerny 

 threw, by use of a concave mirror, and glass lens system concentrated 

 sun's rays which had traveled a 20 cm. water heat filtering tube, into 

 the eye of the rabbit for 10 to 15 sec. The region of the retinal 

 image on exposure was found to be whitened and seared. A section 

 under the microscope showed what he described as a coagulation of 

 the albuminous substances of the retinal elements. 



On the 17th of May, 1882, there was an eclipse of the sun which in a 

 few days brought four cases of sun blinding into Leber's clinic in 

 Gottingen. Deutschmann ^^ at once reported them with a repetition 

 of Czerny's experiment in which he fully confirmed Czerny's findings. 

 One of the four cases used a smoke glass to observe through and 

 another a blue glass, but each received severe injury nevertheless. 

 On ophthalmoscopic examination all four cases showed a character- 

 istic appearance of the macular region varying somewhat in degree 

 corresponding with the degree of injury. In his experiments Deutsch- 

 mann arranged a convex lens to transmit the sun's rays reflected from. 



