EFFECTS OF RADIANT ENERGY ON THE EYE. 737 



the fluid of the anterior chamber also gets some facility at cooling by 

 convection currents. The iris which strongly absorbs most of the 

 energy which falls upon it especially if strongly colored, to a certain 

 extent screens the front surface of the lens behind it especially since 

 the circulatory system in the iris tends to prevent its temperature 

 rising materially unless the access of energy is above the rate at which 

 circulation can take care of it. At the rear of the lens the vitreous 

 with its fibrillated structure effectively prevents, like all such sub- 

 stances, the existence of convection currents. Just what the net 

 effect of the structure is upon the steady distribution of temperature 

 when the eye is exposed to radiation cannot be quantitatively de- 

 termined, and while undoubtedly the heat reaching the rear of the 

 lens from the energy transmitted to that point, or received from that 

 taken up by absorption in the anterior part of the eye, cannot readily 

 escape and hence tends toward concentration it seems somewhat 

 doubtful whether this cause alone could determine the starting of 

 cataract at the posterior cortex. We are inclined to attach more 

 importance to the suggestions of Leber ^^^ that the effect is a secondary 

 one due to the loss of water in the drain produced by the heat on the 

 front of the eye and elsewhere, and especially to that of Parsons ^^^ 

 that malnutrition due to interference with the functions of the ciliary 

 body by the heat may be chargeably w^ith the malady. We are the 

 more inclined to this opinion since the intense radiation acts through 

 the sclera as well as through the cornea, thus aft'ecting the whole 

 structure. It is also a well known clinical fact that diseases of the 

 fundus produce at times cataractous changes in the posterior cortex 

 that are held to be due to impaired nutrition of the lens. The develop- 

 ment of glass blowers' cataract is so slow that it is quite hopeless to 

 reach its cause experimentally, but from the facts here stated we 

 incline to the opinion that these secondary effects of radiation are 

 more important in producing it than the specific action of radiation in 

 producing localized effect at the posterior cortex. In any case it is 

 perfectly clear that abiotic radiations are not concerned, and have 

 nothing to do with the matter. 



Applications to Commercial Illuminants. 



In considering any possible deleterious effects of radiation upon 

 the eye there are certain pathological effects which can be at once 

 eliminated, at least from any consideration of commercial illuminants. 



