130 OBSERVATIONS ON CATARACT ; 
probably extending and growing. In a similar way with my 
second eye the features presented by the Cataract in it were more 
vividly brought out. Removing the perforation, through which 
light was admitted, away from the eye had the effect of substituting 
a smaller perforation. ‘lhe fact might be better understood by 
looking at the perforated piece of metal with which I have ex- 
perimented, and examining the pictures which I have obtained, 
as representations of the Cataract in both eyes, these being 
numbered to correspond with the particular sized perforation 
which had been used in obtaining them. (These exhibits—Plate 
V.—were then examined by the members present). 
The explanation of what I have stated is to be found in the 
following facts :—Any opacity lying between the retina and the 
front of the eye will offer an interference definite in amount 
and character, to any light coming from external illuminated 
objects. This interference willl be the more appreciated by 
the retina as the total quantity of light, a portion of which is 
thus shut off, becomes less. For this opacity in the course of any 
light entering the eye will cast a shadow in front of the retina, 
which will be the more intense in proportion as that light 
which enters the eye, but which does not pass through the 
opacity, and which therefore tends to illuminate this shadow, be- 
comes less. Also, as the shadow caused by this opacity becomes 
more intense, so the outline corresponding to its figure will 
become more distinct, and the different degrees of intensity in the 
shadow, answering to the varying translucency in different parts of 
the opacity, will become more pronounced. 
In conclusion, I do not suppose that I have made a discovery, 
but merely wish to direct attention to facts of my own observa- 
tion, which are not generally known. I will not presume to 
suggest any benefit which may accrue to the professional oculist 
from these observations. A patient may, however, now be able 
to test the progress or otherwise of the Cataract in his own eyes 
and represent for the information of his professional adviser, more 
or less fully and accurately, the shape and character of the ob- 
struction to his vision. ‘This will be of eminent service when 
circumstances prevent the two from confronting each other, and 
in their absence may obviate the necessity of the patient having 
to submit to a tedious operation—the professional examination of 
his eyes by aid of strong light and magnifying glass. Nor does 
the scope of this means of research appear to be limited to cases 
only in which the obstruction to vision is due to Cataract. 
