AGING EFFECTS ON ACCOMMODATION AND OUTFLOW FACILITY RESPONSES TO PILOCARPINE IN HUMANS

Objective: To determine the relationships among age, outflow facility, and refractive and facility responses to pilocarpine in humans. Metho ds: Refraction, intraocular pressure, and outflow facility were determ ined in 30 normal volunteers aged 20 to 75 years, by coincidence refra ctometry, applanation tonometry, and Schiotz tonography, respectively, before and 1 hour after a 30-mu L drop of 2% or 6% pilocarpine. Simpl e regression of baseline facility, postpilocarpine facility, and facil ity change, on age and refractive change singly and jointly, was perfo rmed. Stepwise regression models and graphic conditioning plots were u sed to determine, for each facility variable, its relationship to age or refractive change specifically. Results: Baseline outflow facility and maximum pilocarpine-induced refractive change (ie, accommodation) declined with age, but the decrease in intraocular pressure and the fa cility response to pilocarpine did not. After adjusting for age, for b aseline facility, there was no further relationship to 6% pilocarpine- induced accommodation, and a slight residual relationship to 2% piloca rpine-induced accommodation. After adjusting for both 2% or 6% pilocar pine-induced accommodation, the relationship to age was still signific ant. The facility increase after 2% or 6% pilocarpine did not depend o n age and/or accommodative amplitude. Conclusions: In humans, as previ ously described in rhesus monkeys, an age-related loss of ciliary musc le mobility may compromise the basal function of the trabecular meshwo rk. However, unlike monkeys, humans exhibit no loss of the intraocular pressure or outflow facility response to pilocarpine with age.