| Abstract: | In three of the five achromats examined psychophysically, evidence of three plateaux was found at certain areas of the retina during the normally photopic phase of dark adaptation while the scotopic plateau was normal. These high intensity plateaux coincided fairly well with the photopic phase of our standard dark adaptation curve and the fourth plateau with its scotopic phase. This points to three photopic submodalities and to a normal scotopic mechanism in these achromats. However, the spectral sensitivities, both in the retinal periphery and in the fovea, were maximal between 500 nm and 510 nm for the three photopic plateaux and for the scotopic one and fitted satisfactorily with the 1951 CIE scotopic standard. The mechanisms underlying the appearance of the up to three fast, high-intensity plateaux in the achromats' dark adaptation curves do not fulfill normal requirements completely since they are photopic as to the kinetics of their recovery and scotopic as to their spectral luminous efficiency. The data from the subjects examined indicate three types of receptors with cone kinetics during dark adaptation but containing rhodopsin. The theoretical significance of the findings is discussed, especially why rhodopsin seems to regenerate faster in cones than in rods or in the test tube. Other cases were found, one only illustrated, with only one fast high-intensity plateau similar to those described in the literature.Supported by Stiftung Volkswagenwerk under contract number 11 1538.The Vision Research Laboratory, Hadassah University Hospital and Medical School, Israel. |
