Abstract

Sensitivity to an 18-Hz 20-min of arc test stimulus following a 5-min duration bleach depends on the spectral characteristics of both the bleach and test. When the test stimulus is 656 nm and the bleach is ~60,000 to 70,000 td, equating different wavelength bleaches for L cone quantum absorption causes dark adaptation curves to be identical or similar. Conversely, varying the test wave length following a 660-nm bleach causes profound differences in the shapes of the dark adaptation curves. When the test is 656 nm, sensitivity drops by ~1.8 log unit within ~30 s or less at ~3 min or later after extinction of the bleach. When the test is 540 (one subject) or 470 nm (another subject), sensitivity drops by ~0.7 log unit within ~40 s or less ~1 min or less after extinction of the bleach. When the test is 600 nm, sensitivity decreases gradually by ~1.0 log unit over a span of 10 min or more. To minimize rod-cone lateral interactions, dark adaptation curves were in all cases obtained in the presence of 480-nm annular surrounds (1° i.d.), which followed bleaches of at least 30,000-scotopic td illuminance.

© 1987 Optical Society of America