'1630 VERHOEFF AND BELL. 



The fundamental purpose of this investigation has been to dis- 

 cover what if any pathological effects can be produced upon the 

 structure of the eye by exposure to artificial or natural sources of 

 light. That such action may occur under sufficiently powerful 

 exposure to radiant energy is certain, but the essential fact is the 

 discovery of the quantitative relations between the amount of incident 

 energy and the effects. These relations have generally been left 

 quite out of the reckoning in discussing the subject, with the result 

 of leading to vague and often quite unwarranted conclusions as 

 irrelevant as if one should condemn steam heating as dangerous 

 because one can burn his finger upon a radiator. 



The quantitative phase of the matter is, from a practical standpoint, 

 all-important since on it depends the actual effects to be expected 

 from the exposure of the eye to powerful natural or artificial sources 

 of light. Although the literature of the suljject is very extensive, 

 the appended bibliography covering over 450 titles, practically none 

 of the work done has been quantitative in the sense of connecting 

 the amount and kind of the energ\' received with the effects produced, 

 and hence, despite the work of many careful investigators, the results 

 have been singularly discordant and inconclusive, so that a coordi- 

 nation of the facts from the standpoint of energy has seemed impera- 

 tive. One of us ^^ has investigated recently the energy relations 

 of the radiation from various sources of light both natural and arti- 

 ficial, and the intent of the present investigation has been to determine 

 by actual experiment on the eye the quantitative and qualitative 

 effects of radiant energy on the conjunctiva, cornea, iris, lens, and 

 retina. 



It has long been known that excessive radiation of one kind or 

 another produces pathological changes in the eye, of many kinds and 

 greatly var;)dng degrees of intensity. So far as natural light is con- 

 cerned the well known effects of powerful solar radiation in producing 

 snow blindness and allied troubles have been long familiar as also 

 have been the severe scotomata due to direct observation of the sun, 

 familiar in the literature under the general name of eclipse blindness. 

 With the introduction of the electric arc, mild cases of ocular trouble 

 due to over exposure to the arc began to attract attention, at first 

 nearly a half a century ago, and the subject has occupied an increasing 

 space in the literature ever since. More recently attention has been 

 particularly drawn to the ultra violet radiation as productive of these 

 pathological conditions, and most of the investigations bearing on the 

 general subject have been directed toward the study of the specific 



