Abstract
Purpose:
Eye exposure to the organophosphorus irreversible acetylcholinesterase inhibitor sarin results in long-term miosis (a reduction of at least 50% of pupil width) and reduction in visual function. Anti-cholinergic drugs, such as atropine, are used topically in order to counter these effects and obtain symptomatic relief. Unfortunately, such compounds attenuate ocular discomfort at the expense of producing mydriasis and partial cycloplegia symptoms, which may worsen visual performance. This study was aimed to test beneficial drugs in contradicting the sarin-induced miosis and visual impairment, which will minimally affect vision.
Methods:
Male Pigmented Long-Evans rats were topically exposed to sarin (0.2-1 μg), and 20 min later were topically treated. Pupils were illuminated with an infrared spotlight and images were digitally recorded with a computerized infrared-capable video camera, thus measuring pupil width. Pupil width was determined 15 min -8 h following exposure and treatment. Visual function assessment was performed using the Cued Morris Water Maze task, 15-35 min following sarin exposure and treatment. In this version, cued navigation involves finding a goal location by approaching a single cue that marks the visible goal.
Results:
Rats exposed topically to various sarin doses showed a dose-dependent miosis, which partially recovered within 4-8 h. Oxime treatments with or without the anti-cholinergic drug tropicamide differentially improved the sarin induced miosis and the resulting impairment in visual performance.
Conclusions:
The miotic as well as the visual defects observed, following topical sarin exposure are contradicted to various extent by the treatments used.
Keywords: 503 drug toxicity/drug effects •
405 acetylcholine •
667 pupil