Of almost equal importance to the ophthalmologist are the ophthalmoscope, the retinoscope, and the slit-lamp biomicroscope. The anatomy of the eye lends itself to accurate study by direct observation with various types of illumination. The latter limits the magnification here as it does with all other magnifying apparatus.
The opthalmoscope is undoubtedly the most widely known of these scopes because of its value to general medicine. Méry in 1704 accidently held a cat’s eye under water and saw the blood vessels and color of the retina. In 1851 von Helmholtz reported an instrument which he called the ophthalmoscope by means of which “all the alterations of the vitreous body and of the retina which, until now, have been found in cadavers, will also permit of recognition in the living eye—a possibility which appears to promise the most remarkable advances for the hitherto undeveloped pathology of this structure.” This promise has been more than fulfilled. Now less than 100 years later the examination of the eye-grounds is an important adjunct in the diagnosis of general disease. The ophthalmoscope was a tremendous boost to the medical man’s ability to diagnose vascular disease as well as early cerebral lesions.
The ophthalmoscope is a simple instrument with a perforated disk to look through and a light for illuminating the inside of the eye. Since all eyes are not emmetropic, the lens, which is attached in various ways, is necessary to neutralize errors of refraction of patient and observer.
Although early instruments were obviously. . .