Temporal Effects of 2% Pilocarpine Ophthalmic Solution on Human Pupil Size and Accommodation

First responders and those who work with organophosphate (OP) compounds can experience ocular symptoms similar to those caused by exposure to low levels of nerve agents. This study was designed to examine the efficacy of a safe, clinically available, simulant that reproduces ocular symptoms associated with low-level OP exposure. Among these ocular symptoms are a constriction of the pupils (miosis), decreased visual acuity, and changes in accommodation.

Volunteers aged 18-40 were assigned to groups receiving either a two-drop or three-drop dose of FDA approved 2% pilocarpine ophthalmic solution. Baseline visual performance measurements were taken before eye drop instillation and a timer was started following the first drop of pilocarpine. Once eye drops were administered, visual performance including distant and near vision, pupil size, and accommodation were measured every 5 minutes for 2 hours.

Both groups experienced significant miosis in excess of 90 minutes. Visual acuity was significantly reduced because of accommodative changes. The three-drop group experienced longer lasting combined effects when compared to the two-drop group.

2% pilocarpine ophthalmic solution can safely simulate major ocular symptoms of OP exposure for behavioral research studies for at least 60 minutes.