EFFECTS OF RADIANT ENERGY ON THE EYE. 787 



Very recently Behr ^^ has found marked reduction in the Hght 

 adaptation power in four patients complaining of visual disturbances 

 after continued work by arc light and strong incandescent lights. 

 They noted that after working by these lights and then moving to a 

 darker part of the room that they could hardly see to work at all, 

 or on coming out into sunlight everything appeared gray or dark. 

 In twilight or after a rest in darkness the vision improved slowly only 

 to receive another setback on further exposure to the artificial light. 

 These patients were tested on the Piper instrument for measuring the 

 dark adaptation power. Normally as Piper has shown there is a slow 

 increase of sensitiveness during the first 61 to 10 min. in the dark 

 and then a sudden marked increase in 30 to 35 min. followed by a 

 further slow increase until after 45 min. the maximum light per- 

 ception sensitiveness is reached. Behr found in none of these cases 

 was there much increase of sensitiveness after 10 min. and at the 

 end of 45 min. was still | to | of normal. These cases were advised 

 to work less by strong artificial lights and Euphos glas was prescribed. 

 Mild light such as oil lamplight was advised where possible. Three 

 of the patients were presumably cured because they made no further 

 complaint, while the fourth whose case was followed, regained in a 

 short time a light adaptation that was better than normal. 



Erythropsia or Red Vision. 



Hildige ^^^ in 1861 noted erythropsia in snow blinding. Mayer- 

 hausen'^*^ and Steiner^^° in 1882 reported cases after blinding by 

 lightning and short circuiting and by the sun's rays both directly and 

 indirectly as from water surfaces or from snow. Cases which occurred 

 after cataract operations were further reported by Dimmer ^^ and 

 Putscher ^^^ in 1883. Widmark in his correlation of electric ophthal- 

 mia and snow blinding noted that erythropsia occurred in both but 

 did not investigate the subject further. Fuchs ^^^ in his monograph 

 of 1896 emphasized the role of ultra violet light in all these cases espe- 

 cially in cases of snow blinding, aphakia, and electric ophthalmia. 

 Using the fact that established by Kuhne ^^^ and Konig two years 

 before, that the visual purple is most rapidly bleached by rays below 

 500 jjLfx. Fuchs advanced the theory that the regenerating visual 

 purple accounted for the red vision as an entopic phenomenon. 

 Schulek^^^ produced Erythropsia by observing spectral ultra violet 



