464 
POPULAE SCIENCE EEVIEW. 
Stroud. In tlie liealtliy eye the aqueous humour, leus, and 
vitreous humour are clear, and do not in any way obstruct the 
passage of the light. It is otherwise in disease ; and this 
brings us to the discussion of some of the practical applica- 
tions of the ophthalmoscope. Here, perhaps, I may be per- 
mitted to quote some of the paragraphs of a paper which I 
read lately on the subject before the Harveian Society. 
Taking up the diagnosis of the various forms of disease, any of which 
would have been held to constitute the condition known as amaurosis, it may 
be noted, first of all, that, even in the hands of the novice, ophthalmoscopic 
examination supersedes those chapters in ophthalmology which were formerly 
devoted to the means of distinguishing between incipient cataract and 
amaurosis. In the past, and even at present, with those surgeons who are 
content to treat deep-seated diseases of the eye by guessing at their nature, 
and have not adopted the systematic use of the ophthalmoscope into their 
practice, the functional annoyances which commonly occur at the outset of 
the formation of lenticular cataract, have been, and are, fertile sources of de- 
ception. The patient complains of frontal paia, of confused vision, stars of 
light, and some other vague symptoms which characterize the outset alike of 
many forms of deep-seated disease of the eye, and of the fatty degeneration 
of the lens which commonly gives rise to lenticular cataract, probably from 
coincident swelling of the lens. An error arising from this source has many 
times condemned the unfortunate subject of a commencing cataract to the 
severe treatment thought appropriate to the unhappy class of amaurotics. 
The kind of alteration in the lens, imperceptible by any other means than 
the ophthalmoscope, is the slightly opaque striation of the substance of the 
lens sometimes seen in an early stage. These opaque striae may occupy 
either the anterior or the posterior segment of the lens, and spring from the 
centre of the crystalline or converge towards the centre from the circum- 
ference. In order to see the latter, the pupil must be fully dilated with 
atropine ; as, indeed, for the purposes of complete ophthalmoscopic examina- 
tion it always needs to be ; and then, just as the greatest expert cannot 
discover them except by ophthalmoscopic illumination, so, neither with its 
aid, can they be passed over with ordinary care. In order to be quite sure in 
any delicate case, it is well to lower the light a little, and use only a feebly 
illuminating power, as a very strong light may overpower a commencing 
opacity, and render us unable to detect the striae. This practical caution 
applies equally to all other conditions of opacity in the transparent media. 
In two cases lately I have been able to set at rest doubts of this kind, which 
happened to be in the persons of medical men, who were much disquieted by 
the symptoms — one a member of this Society. In a third case I have 
recently detected incipient cataract (peripheric striae) in a gentleman supposed 
to be suffering from commencing glaucoma. 
It is of frequent occurrence to find the capsule of thn lens stained with 
black spots : these are stains left by the uveal pigment, and occur usually 
after an attack of iritis, when the iris has been in contact with the lens. 
When the iris has been adherent, a complete ring of pigment may often be 
