Ophthalmoscope, << of THAL muh skohp, >> is an optical instrument for examining the interior of the eye. Ophthalmologists and optometrists can make certain diagnoses by using the ophthalmoscope to examine abnormalities in the eye.
There are two types of ophthalmoscopes, the direct ophthalmoscope and the indirect ophthalmoscope. The direct ophthalmoscope contains a light, a prism and a mirror, and lenses. These parts are mounted in the head of the instrument, which is attached to a handle containing a battery. The prism and mirror project the light on the back of the eye. The lenses enable the examiner to focus the light to provide a clear, magnified view of the eye’s interior. The indirect ophthalmoscope consists of a light worn on the examiner’s head and a lens held in front of the patient’s eye. This instrument enables the examiner to see a larger area than the direct ophthalmoscope does, but with lower magnification.
The ophthalmoscope was invented by a German physicist, Hermann von Helmholtz, in 1851 (see Helmholtz, Hermann L. ). Helmholtz’ instrument consisted of a sandwich of three thin plates of glass mounted at a 45-degree angle on a handle. A light was placed to the side of the eye under examination. Some light passed through the glass plates, but some was reflected into the eye. The lighted inside of the eye was observed through the glass.
