I call attention to the power of the pinhole disc found in trial cases in the examination of the eye. All are familiar with its use in detecting myopia and high degrees of hyperopia; and it is well known that if there is light enough and the opening of the screen is small enough, there would be no need of lenses in any condition of refraction, at any age. The pinhole disc does its work by lessening the diffusion circles on the retina; and too small an opening in a retinoscope or ophthalmoscope is a disadvantage because its masks errors of refraction.
In Foster's "Text-Book of Physiology" we find it stated that if the pinhole disc is held before the eye and moved laterally, the experimenter looking toward the bright sky, the retinal capillaries may be seen, looking like a cobweb. The vessels at right angles to the
TENNEY JA. SUBJECTIVE REFRACTION. JAMA. 1904;XLIII(27):2030–2031. doi:10.1001/jama.1904.92500270002h
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