Abstract

The influence of rod- and cone-stimulating adapting flashes (AFs) on the visibility of 18 cycles/deg square wave gratings was determined in the foveal and parafoveal retina. The threshold grating luminance (i.e., the TGL, luminance, luminance of the 54-min of arc diam 10-ms duration test grating just permitting detection of grating orientation) served as an index of spatial acuity. TGL was determined at many time intervals in respect to the onset and offset of the 20° diam 500-ms AF. Rod-stimulating (<1-scotopic td) AFs decrease TGL (enhance acuity); this effect gradually increases to a maximum value 250 ms after AF onset and wanes to a negligible value several hundred milliseconds after AF offset. Cone-stimulating AFs increase TGL (reduce acuity) several hundred milliseconds prior to and during AF presentation. But within 400 ms after AF offset, TGL is lower (acuity enhanced) than control value, returning to control level ~1 s later. With no AF present, the action spectrum for TGL adheres to the sensitivity of the CIE photopic observer; when enhanced by either rod or cone stimulating AFs, the action spectrum for TGL exhibits enhanced long-wavelength sensitivity.

© 1987 Optical Society of America