Z PROCEEDINGS OF THE AMERICAN ACADEMY. ' 



injury which has come to be known as ophthalmia electrica. It is in 

 effect a superficial sunburn of the eye and is often accompanied by a 

 simihir sunburn in the vicinity of the affected eye. Whether this 

 particular sort of effect is produced also by ultra violet rays of slightly 

 greater wave length, say up to 320 fxfj. or 330 /x/x, is a matter of some 

 dispute, but most investigators have held this particular region under 

 suspicion on account of the phenomena of snow blindness, which 

 closely resemble those of the so-called ophthalmia electrica, and cannot 

 be produced by the extreme ultra violet rays since the solar spectrum 

 owing to atmospheric absorption is extremely weak at and below 300 

 fi^, very near to which point it is wholly cut off. It is, however, 

 fairly rich at 320 to 330 jjfx, the cutting oft" by atmospheric absorption 

 being rather sudden, as shown in a, Plate 1. 



Now while the cornea cuts oft' only rays of wave length less than 

 300 idfi the lens of the human eye ordinarily absorbs the whole ultra 

 violet, it being substantially due to this absorption that we are unable 

 to see beyond the violet. This absorption extends to about wave 

 length 380 yu^u and in old persons in whom the lens gets slightly yellow 

 even as far as wave length 420 yu/x. In early youth there is a very 

 slight transmissibility of the lens in the region 315 to 330 /jl/j. as 

 shown by Hallauer.^ Now potentially the rays which are absorbed by 

 a medium may produce changes in it and the ultra violet rays up to 

 and including the extreme violet have been reputed by various writers 

 to produce a large variety of lesions, including retinal injury due to the 

 rays which may filter through the lens. The list of reputed dangers 

 is a very long one including erythropsia, color scotomata, cataract 

 and other serious results. The situation from the point of view of the 

 ophthalmologists who seem to be really in fear of ultra violet radia- 

 tions is well summed up by Schanz and Stockhausen.- Other writers 

 like Best ^ and Voege'* attach relatively little importance to the effect 

 of the ultra violet as such and are inclined to attribute some of the 

 phenomena to over-intense radiation of ordinary light or to causes 

 not connected to radiation at all. 



A third group, of which Birch-Hirschfeld ^ is a representative, 

 holds an intermediate view. It should be noted that the permanent 



1 Klin. Monatsbl. f. Augenhcilk., Dec. 1909. 



2 Ztschr. f. Augenheilk., Mav 1910. 



3 Klin. Monatsbl. f. Augenhcilk., May 1909. 



^ Die Ultravioletton Strahlen der modernen kiienstlichen Lichtquellen und 

 ihre augenbliche Gefahr fur das Auge. Berl., 1910. 

 * Ztschr. f. Augenheilk., July 1908, and elsewhere. 



