Dark adaptation is the increasing sensitivity of the eye to light in a totally dark room. It is a function of the choroid and of the bacillary layer of the retina. The smallest amount of light that is visible to the dark-adapted eye is called the "light minimum" (L. M.). Other terms used synonymously are "minimum light visible" (M. L. V.) and "light threshold" (L. T.). With light difference, which is a function of the conducting apparatus, this paper is not concerned.
In July 1934 I1 described a self-registering instrument for taking the light threshold, and a dark adaptation graph was drawn charting this behavior of the eye with various periods of total darkness. The range of light necessary for the normal as well as for the moderately pathologic eye with a contracted pupil was found by trial and error to be between 0.000,001 millilambert (1 micromillilambert) and 0.13
FELDMAN JB. DARK ADAPTATION AS A CLINICAL TEST: THE TECHNIC AND THE RESULTS. Arch Ophthalmol. 1936;15(6):1004–1019. doi:10.1001/archopht.1936.00840180048005
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