The influence of intermittent versus continuous preadaptation upon subsequent dark adaptation was investigated for two durations of the continuous: and 3 minutes. The rate of intermittence for the discontinuous condition was 1 cycle/second and four light-to-dark ratios were employed. The pre-exposure intensities were 8860, 886, 88.6, and 8.86 mL. Differences were found for most of the cases in which a comparison was made between the curves of dark adaptation following the two conditions of preadaptation. For the intermittent condition at the highest pre-exposure intensity it was found that the shorter the light-time in the ratio, the lower the initial threshold tended to be and the more rapidly the final dark adapted threshold was reached. At the two lower intensities the initial thresholds for both the intermittent and continuous curves were approximately the same, but the curves for the intermittent were markedly retarded in reaching the final level of dark adaptation.
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