Pupil Response as an Objective Measure of Visual Acuity*

Abstract

Pupillary responses to brief presentations of sinusoidal grating patterns were measured. The results show that the amplitude of the pupillary responses varies systematically with grating spatial frequency. Gratings of spatial frequencies in the range 1-5 c deg-1 elicited the maximum percentage change in pupil area, with higher and lower spatial frequency gratings producing smaller responses. The bandpass nature of the pupil response function was compared to contrast sensitivity functions obtained under the same viewing conditions. The effects of defocus and eccentric fixation on both contrast sensitivity and pupil response functions were qualitatively similar. Grating acuities calculated from contrast sensitivity data correlated well with similar data extracted from pupil response functions. The results suggest that automated pupillometry can provide an attractive means for objective measurement of visual acuity.

Pupil response as a predictor of blindsight in hemianopia

“…To quantify the response amplitude, previous studies have marked the points of deflections indicating the start of pupil and points of maximum constrictions by visual inspection. The calculated difference in pupil diameter between the two points is taken as the response amplitude (8,11,15). Although the technique has high interexperimenter reliability (28), it is nevertheless subjective and open to bias.…”

“…The pupil response amplitude after the onset of a checkerboard pattern is systematically modulated by the square size in the checkerboard, with no responses present at below the limits of visual acuity (10). In healthy adults, the sudden onset of grating patterns also leads to a transient constriction of the pupil, and the profile of response amplitudes varies with spatial frequency similar to that of the contrast sensitivity function (11).…”

Changes in color vision with decreasing light level: separating the effects of normal aging from disease

“…The instrument employs infrared video imaging techniques to measure the center coordinates of the pupil and compute its size [30] A pulsed, infrared illumination system is used to illuminate the iris for ∼4 ms within each image frame in order to eliminate pupil image smear caused by eye movements. The system is focused as the patient fixates the center of the screen.…”

Task and information conflicts in the numerical Stroop task

“…In total, the brightness of the rectangles was less than that of the other stimuli, and less brightness (or more darkness) leads to larger pupil dilation (Ellis, 1981). In addition, the spatial frequency of the colored rectangles was smaller than that of the other stimuli and low spatial frequency (compared to high spatial frequency) leads to larger dilation of the pupil (Barbur & Thomson, 1987). Hence, if colored rectangles resulted in smaller dilation (compared to other conditions), it would not be due to their perceptual features.…”