Objective: To test whether pupil escape observed during a constant light stimulus was greater in eyes with central visual field loss compared to eyes with peripheral visual field loss and normal eyes.
Design: Comparative, observational case series.
Participants: Twenty-seven normal subjects, 5 patients with central field loss, 11 patients with peripheral field loss, and 8 patients with combined loss (central and peripheral visual field loss) were tested.
Methods: A dual-channel infrared pupillograph was used to simultaneously record the right and left pupil diameters at a rate of 60 Hz to characterize the initial, phasic pupil contraction, and the sustained, or prolonged, pupil contraction in response to a 5-second light stimulus. Full-field light stimuli with a diameter of 30 degrees were presented to each eye at seven different intensities.
Main outcome measures: The amplitude of the phasic pupil contraction was compared with the amplitude of the sustained pupil contraction at the four brightest intensities (slope of phasic versus sustained contraction) in the normal eyes and in eyes with visual field loss in the center and the periphery.
Results: The sustained pupillary contraction showed a statistically greater reduction in proportion to the phasic component in eyes with central field loss compared to those with peripheral field loss, combination central and peripheral field loss, and normal eyes.
Conclusions: Afferent neurons from the central retina normally contribute a substantial component to the sustained pupil response. Eyes with central field loss can be distinguished from eyes with peripheral field loss by a relatively greater loss of the sustained response, causing greater pupil escape. This study showed that pupil movements in response to a nonperimetric full-field light stimulus may provide some degree of mapping of retinotopic sensitivity. This information may be of use in interpreting the pupillary movements during the swinging flashlight test and may help predict the pattern of visual field loss.