Purpose: An objective, pupillographic photostress test was developed to assess the initial sensitivity loss and its rate of recovery in healthy eyes and in eyes affected by optic neuropathy.
Methods: Pupillary light reflexes were recorded with an infrared pupillometer after a binocular photostress that subtended 30 degrees of the central visual field. The initial loss of light sensitivity (in log units) and its recovery with time were derived by analyzing subsequent increases in pupil contraction amplitude to a series of alternating light stimuli. The effects of photostress duration and intensity were studied in ten control subjects. Photostress recovery also was compared between eyes of nine patients with unilateral optic neuropathy.
Results: In the ten control subjects, increasing photostress duration caused significantly increased sensitivity loss at time zero after the photostress (analysis of variance), but did not significantly affect the exponential recovery rate. Intense photostress brightness caused more initial sensitivity loss than did dimmer photostress lights. In addition, half-time of sensitivity recovery was prolonged after the brightest photostress. In nine patients with unilateral optic neuropathy, a 120-second photostress caused significantly less initial sensitivity loss in the affected eye than in the healthy fellow eye.
Conclusions: The pupil photostress test objectively can measure the eye's loss of light sensitivity after a photostress and its exponential rate of recovery. Loss of optic nerve function diminishes the initial stress-induced loss of light sensitivity and does not significantly affect the poststress rate of recovery in the patients tested.