Eyesight, and how to care for it / edited by George Black.

Date:
[1888]
Catalogue details

Licence: Public Domain Mark

Credit: Eyesight, and how to care for it / edited by George Black. Source: Wellcome Collection.

    52/168 (page 48)
    Having managed to light up the interior of the eye, and to perceive the light reflected from it out through the pupil, it only remains to focus this light accurately on our own retina in order to see distinctly every object from which it comes. This is accom- plished by means of small lenses, of different focal distances, placed immediately behind the opening in the mirror. This forms, substantially, the ophthal- moscope now in general use, which gives a distinct and magnified view of the interior of the eye, and reveals to actual inspection many diseased conditions which were formerly the subjects of theoretical spec- ulations. The lenses also afford the means of meas- uring the focus of the eye examined. The uses of the ophthalmoscope are not confined to ophthalmic surgery, but physiologists have availed themselves of its aid to study the circulation in the only blood-vessels in which it can be seen during life, and general diseases are often detected by the changes that they make in the appearance of the retina and optic nerve. This is particularly true of diseases of the brain, for the ophthalmoscope enables us to in- spect a large nerve within a.short distance of its origin in the brain, and one that is wrapped in membranes and contains blood-vessels derived directly from those of the brain itself.