Contrast sensitivity as a function of position on the retina.

Contrast sensitivity has been measured as a function of the eccentricity along several meridians. The measurements were carried out with a two-dimensional sinusoidal grating (cross grating) presented in a surround with a luminance equal to the average stimulus luminance. The advantage of this stimulus over a one-dimensional grating is that it permits presentation of small-sized stimuli. in a surround of the same luminance, without discontinuities at the edges of the stimulus. The results appear to be comparable with contrast sensitivity data obtained with one-dimensional gratings, The decrease in sensitivity is found to be dependent on the meridian along which it is measured. Plots of equal sensitivity curves show that these curves are somewhat ellipsoidal.