Some factors producing individual differences in dark adaptation

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Abstract
Dark adaptation was detd. over a period of 20 min. for a white intermittent stimulus of 0.2 sec., centrally fixated, and subtending a visual angle of 121/2o. Perception time designates the time taken from the onset of darkness to see each of the selected brightnesses of the test patch. All subjects were free of gross optical and other abnormalities. Possible vit. A deficiency was eliminated by systematic dosage. Correlation of pupil diam. in the light with perception time gave 15 significant positive correlations for 17 test-patch brightnesses. Therefore, a comparatively large pupil in the light produces a retardation of dark adaptation. The correlation of pupil diam. in the dark with perception time for 6 selected test-patch brightness was not significant. This was due to a significant correlation between pupil diam. in the light and that in the dark. Comparatively large pupil diam. in the dark tends to decrease perception time. No significant coefficients resulted from correlation of general coloring or of visual acuity with perception time. Correlation of retinal pigmentation, judged by the difficulty of seeing the choroidal vessels, with perception time gave 6 negative coefficients of which 2 were significant. Heavy pigmentation of retina favored more rapid dark adaptation.

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