Retinal limits to the detection and resolution of gratings

TLDR

The study determined the maximum spatial frequency for detecting and resolving sinusoidal gratings as a function of stimulus location across the visual field. Stimuli were generated directly on the retina as interference fringes to avoid image degradation from the eye’s optical system. Subjects could detect gratings at spatial frequencies up to three times the resolution limit at 5° eccentricity and up to ten times at 35°, indicating that detection is limited by cone size while resolution is constrained by beta ganglion cell spacing.

Abstract

The maximum spatial frequency for the detection and resolution of sinusoidal gratings was determined as a function of stimulus location across the visual field. Stimuli were produced directly on the retina as interference fringes, thus avoiding possible loss of image quality, which may occur when the optical system of the eye is used to form the retinal image. Contrary to earlier reports, we found that subjects could detect gratings with spatial frequencies much higher than the resolution limit. At 5° of eccentricity from the fovea, the detection limit was about three times the resolution limit, and this factor increased to about 10 as the test stimulus was moved 35° into the periphery. Quantitative comparison of the data with retinal anatomy and physiology suggests that pattern resolution is limited by the spacing of primate beta (midget) retinal ganglion cells, whereas pattern detection is limited by the size of individual cones.