Abstract

It has been known since the classic work of Wertheim (1891) that visual resolution in the periphery falls off so rapidly that at 20° of eccentricity acuity is reduced by the factor 10 relative to the fovea. Although optical quality deteriorates somewhat in the periphery, evidently a broad range of spatial frequencies may be present but not resolvable in the peripheral retinal image. One wonders what role, if any, these image components play in peripheral vision. During experiments designed to measure resolution in the periphery it became evident that this band of frequencies was more a range of confusion than a range of invisibility. When confronted with a grating well above the resolution limit, subjects were confident that a spatial pattern was present because they could perceive contrast. With practice it became possible for some individuals to perceive, for a fixed stimulus, a cavalcade of gratings of rapidly changing orientation and relatively low spatial frequency. This perceptual ambiguity vanished when the stimulus frequency was reduced to a value near the accepted limit for grating resolution. The most likely explanation for these observations is aliasing caused by the relatively low sampling density of neurons in peripheral retina.

© 1985 Optical Society of America