Subsensitivity to pilocarpine in primate ciliary muscle following topical anticholinesterase treatment.

Accommodative responses to intramuscular pilocarpine were determined in four surgically aniridic vervet monkeys, before and after eight weeks of daily unilateral topical treatment with echothiophate iodide. The echothiophate-treated eyes maintained maximum myopia during the treatment course. However, after echotiophate treatment was stopped and the refraction had returned to baseline, a subsensitivity of the accommodative mechanism to pilocarpine became apparent. Normal sensitivity to pilocarpine did not return until four to five months after echothiophate treatment had been stopped.