Extrafoveal Visual Acuity as Measured With Snellen Test-Letters

The Topography of Vision in Mammals of Contrasting Life Style: Comparative Optics and Retinal Organisation

“…Several authors [POLYAK, 1941;LUDVIGH, 1941;DOESSCHATE, 1946;(Fig.43), LE GRAND, 1967] then found satisfactory agreement to extend for only a degree or two of eccentricity, acuity subsequently falling off more rapidly than cone separation (Fig.23--6). Even when the possibility of optic impairment of resolution is eliminated by the use of interference fringes as stimuli, it is found (GREEN, 1970) that cone separation and the sampling theorem account for the attained neural resolution over no more than 2° from the fixation point.…”

Parametric adjustment in saccadic eye movements

“…This performance is all the more remarkable when one considers that the time involved (.04 sec) is far too short for the operation of any exteroceptivf eedback loop which might guide the eye to the target in successive approximations (Dodge & Cline, 1901, p. 149); that the visual acuity 10 0 from the fovea is only 1/5 of what it is at the fovea (Ludvigh, 1941); and that the eye is lacking in articular sensitivity (Merton, 1964). Furthermore, because of variations in such parameters as fatigue, starting position of the eye movement, and resting tonus of the muscles, a given pattern of innervation may produce different amounts of ocular rotation at different times.…”

The Main Sequence of Saccades Optimizes Speed-accuracy Trade-off

“…Due to the extrafoveal fall-off in photoreceptor density, visibility of a visual target decreases rapidly with foveal eccentricity as small as a few minutes of arc, as measured by contrast sensitivity or letter acuity (Herse and Bedell 1989;Ludvigh 1941). Thus, position error decreases visibility.…”