Influence of central depressant drugs on pupil function: an evaluation with the pupil cycle induction test

Afferent pupillary defect is an early sign of optic nerve or chiasm disease. It can be evaluated by the Pupil Cycle Induction Test (PCIT) which assesses the difficulty in setting up regular and sustained pupil oscillations. PCIT was carried out in 30 subjects with presumably normal visual function (normal visual acuity and normal fundi) and taking benzodiazepines and/or barbiturates. In 42 out of the 60 tested eyes, response to PCIT was altered. This emphasizes the necessity of a detailed drug-taking history when investigating anterior visual pathways by means of pupil function, especially when one considers the extensive use of central nervous system depressant drugs by the general population.