Sensitivity of the blue-sensitive cones across the central retina.

We measured increment thresholds up to 5 degrees eccentricity using a 10' dia flash viewed against 10(4) td of 572-nm background. We found two distinct sensitivity profiles, one with flash wavelengths 410-470 nm and another with 520-580 nm. Spectral sensitivity plots indicate blue-sensitive cones and green-sensitive cones for the two profiles, respectively. Sensitivity of blue-sensitive cones is maximum at 1 degree eccentricity. Measurements at greater eccentricities are susceptible to adaptation to test field. The light-collecting area of blue-sensitive cones raised to a power follows the sensitivity profile of blue-sensitive cones.