Reduced Pupillary Sensitivity to Topical Phenylephrine Associated with the Relaxation Response

Abstract

Human pupillary dilatation after topical instillation of phenylephrine was assessed in a prospective, randomized, controlled experiment to measure alterations in α-end-organ responsivity after regular elicitation of the relaxation response. Baseline pupillometric measurements were taken in both experimental and control subjects. The experimental subjects then practiced daily a technique that elicited the relaxation response while the control subjects sat quietly for comparable periods of time without eliciting the relaxation response. After four to six weeks, both groups returned to the laboratory for an assessment identical to that of the first visit. Comparison between visits revealed that the pupillary dilatation in the experimental group was significantly diminished (p < .02) as compared to that of the control group. This observation is consistent with reduced end-organ responsivity to an exogenous α-adrenergic agent after regular elicitation of the relaxation response.

Index Terms:

• pupillometry
• relaxation response
• phenylephrine
• sympathetic nervous system