Abstract

S-cone increment thresholds are strongly affected by the state of adaptation of all three cone types. Models of opponent and nonopponent mechanisms suggest that decreased lateral inhibition affecting all pathways equally could selectively elevate S-cone increment thresholds. Therefore, S-cone increment thresholds do not provide unambiguous evidence of selective S-cone-pathway damage. To evaluate S-cone function in patients in conditions in which lateral inhibition is insignificant, S-cone grating orientation acuity functions were gathered with a 500-nm 0.9-log td test field and a 590-nm 4.6-log td adapting field. S-cone acuities for twenty-five normal subjects were comparable with anatomical data on individual variations in the SWS-cone mosaic. For thirty-four normals and patients, test fields were reduced as much as 1.5-log unit; conversion to S-cone contrast indicated that S-cone resolution did not vary with S-cone adaptation state. Varying L/M-cone adaptation state (using lower adapting field luminances) also did not affect S-cone resolution. These data suggest that the high frequency limb of the S-cone-mediated contrast sensitivity function is relatively unaffected by adaptation state and provides an important complement to clinical S-cone increment thresholds.

© 1991 Optical Society of America