Investigative ophthalmology & visual science
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To investigate the autonomic components of the pupillary light reflex in humans, we used infrared pupillometry combined with a partial local cholinergic (tropicamide) or alpha-adrenergic (thymoxamine) blockade. The pupillary response curve was analyzed using parameters identical or similar to those employed previously to study the autonomic components of the pupillary light reflex. ⋯ We found the expected cholinergic contribution to the constrictive phase of the pupillary light reflex but no evidence for peripheral alpha-adrenergic activity during redilation. We propose that redilation primarily involves parasympathetic relaxation, modulated by cholinergic inhibition of the dilator muscle and central sympathetic inhibition of the Edinger-Westphal nucleus.