ophthalmoscope(redirected from direct ophthalmoscope)
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ophthalmoscope(ŏfthăl`məskōp'), instrument used for examining the inner structure of the eyeeye,
organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many other
..... Click the link for more information. . The device was invented by the German physiologist H. L. F. von Helmholtz in 1851. His model consisted of three plates of glass pressed together and mounted on a handle at a 45° angle. A light was placed beside the subject whose eyes were to be examined. Some light passed through the plates, but some was reflected back into the eye. The form of the instrument now in general use consists of a concave mirror and a battery-powered light source within a tubular handle. Sighting is through a single or binocular eyepiece. The ophthalmoscope is equipped with a rotating disc of lenses to permit observation of the eye at varying depths and magnifications. Examination of the eye may be enhanced by administering drugs to dilate the pupil.
An instrument, consisting essentially of a concave mirror with a hole in it and fitted with lenses of different powers, for examining the interior of the eye through the pupil.
an instrument for examining the interior of the eye