Absolute spectral sensitivity at different eccentricities.

Abstract

Absolute spectral-threshold functions were measured during the cone-plateau period and in a dark-adapted state at 0, 6, 17, 28, 45, and 65 degrees temporally to the fovea. It was found that, when the photopic functions were brought together at 660 nm, they closely coincided in the 520-700-nm region of the spectrum, irrespective of location, suggesting that the relative spectral sensitivity and the weighted contributions of the middle-and long-wave cone photopigments remain invariant across the retina. On the other hand, the results suggest that the relative contribution of the short-wave cone mechanism increases between fovea and 17 degrees, stays essentially constant between 17 and 28 degrees, and decreases between 28 and 65 degrees. Furthermore, the results suggest that the absolute sensitivity of the middle- and long-wave cones decreases between fovea and 65 degrees, whereas the absolute sensitivity of the rods increased form fovea to 17 degrees and decreases between 17 and 65 degrees degrees. Finally, the log difference between the absolute dark-adapted cone and the rod threshold was found to increase between fovea and 45 degrees and to decrease between 45 and 65 degrees.