Edge-light pupil cycle time and optic nerve disease

Edge-light pupil cycle time is a quantitative measure of pupil reaction to light, dependent on the functioning of the afferent arm of the pupillary reflex arc. It has been used as an objective assessment of optic nerve function in various neuroophthalmic diseases. In this study, pupil cycle times were determined on 60 eyes of 30 normal subjects, and a mean value of 814 ms with an upper limit of normal at 935 ms was established. The average difference between the two eyes was 34 ms, and the upper limit of normal was 79 ms. Pupil cycle times were then performed on ten eyes with optic atrophy, and all ten (100%) had abnormal values. Nine patients with multiple sclerosis were tested and abnormal cycle times were found in 15 of 18 eyes (83%). Five additional patients with questionable diagnoses were tested, and all but one had abnormal pupil cycle times. A discussion of pupil reactions in optic nerve disease is presented, and the value of edge-light pupil cycle time as a quantitative measure of nerve function is assessed.