Visual Acuity as a Function of Intensity and Exposure-Time

Central field perimetry of discriminated targets: I. Results for normal individuals using high-contrast targets

“…These results, obtained on naïve individuals, are similar to that determined in prior investigations of laboratory investigators using sinusoidal gratings, 34,35 Landolt C rings, [37][38][39][40] and Snellen letters [41][42][43] with similar presentation times. Similar to most authors, we also showed a linear deterioration of acuity with eccentricity.…”

“…This difference may have been due to the short presentation time of the Landolt Cs (250 ms) compared with the average duration of fixation that is usually taken to read each letter of the acuity chart (usually to 0.5-1 s or more). 34 Discrimination of targets at fixation has been shown in prior studies to require longer presentation times than that required for detection, 34 but has been observed to be independent of the presentation time in normal eyes for times longer than 180 ms. 35 The relatively larger acuity, determined by the Landolt C thresholding method, in this study may also have been due to the methodology for thresholding or to the use of white letters against a black background, which in a darkened room would result in relative pupil dilation and poorer resolution. However, this may have been offset by the reduced glare compared with a black letter presented against a white background.…”

The effect of optotype presentation duration on acuity estimates revisited

“…Graham and Cook [1] assessed acuity estimates as a function of presentation duration, but not for durations longer than 1 s. Monjé and Schober [2] found a sizable increase in acuity with presentation duration in the interval of 10 ms to 50 ms, which is far below those durations typically used in practice. Zanen and Klaassen-Nenquin [3] did not find a difference between a 1-s presentation and a "pause" condition.…”

Visibility of a Fine Line in Intermittent Illumination

“…He took into account the modification involved in the mean intensity when the flash duration becomes an appreciable fraction of the total presentation time and also the effect of duration of stimulus on the visual effect of a light as described by Graham and Cook [7]. His experiments, with these refinements, confirm the findings of Senders, that is, visual acuity is improved in intermittent illumination except for very short exposures of the field.…”