80 Scientific Proceedings, Royal Dublin Society. 
Listing and subsequently Donders classified the various entoptic 
appearances seen in the crystalline and the anterior part of the 
eye. Excellent drawings of these are given by Donders, 
and more especially by Helmholtz.’ But, as already remarked, 
it is surprising that none of these eminent men noticed the 
great value of entoptic observation in the case of cataract. 
I cannot lay claim ‘to the first. discovery of this, for, though 
it was independently observed by myself, Dr. Darier, of Paris, 
appears to have been the first to draw a cataract thus observed 
some ten years ago. In a paper he published in a French 
journal, Dr. Darier says he accidentally noticed an obscurity in 
one of his own eyes when he viewed a point of light ; he was thus 
led to make an arrangement, consisting of a concave lens and a 
distant candle, for the better examination of his erystalline.? This 
arrangement he called an autophakoscope; unfortunately, he 
appears to be quite unaware of the literature or the theory of 
entoptic observation, and also of the generally accepted termin- 
ology ; he gives, however, some drawings of what he observed, 
and is convinced of the value of the method in ophthalmology. 
It does not, however, need any instrumental appliances to see 
one’s own crystalline lens. Various simple methods of doing so 
were mentioned in Part I.,§ 1. One of the best and simplest is 
a point of light reflected from some portion of the polished rim 
of a pair of spectacles worn by the observer, especially when a 
bright source of light is behind the observer. ‘The homocentric 
pencil of rays thus obtained enables entoptic phenomena to be 
well seen, so that if the observer has used the Huntoptiscope, and 
is familiar with what he is to look for, he can readily see his own 
crystalline, any opacities within his eye, and the changes in the 
magnitude of his pupillary dise by merely looking at one of the 
brilliant spots of light reflected from the rim of his own spectacles. 
(7). Reference has already been made in § 5 to the ease with 
which the Entoptiscope enables the musce volitantes to be seen and 
their position in the eyeball found. In this case No. 2 or No. 3 pin- 
1 See Donders, Accommodation and Refraction of the Eye, p. 200; Helmholtz, Optigue 
physiologique, pp. 208 et seq . 
_ 2&¢De la possibilité de voir son propre crystallin,’ par M, le docteur Darier- 
Annales d’ Oculistique, September, 1895, vol. cxiv., p. 198. See Note on p. 83. 
