Pharmacologic Effects on the Pupil

Abstract

Pupil-active agents are autonomic drugs that affect the pupil by altering either the sympathetic innervation of the dilator pupillae or the parasympathetic innervation of the pupillary sphincter. In both the sympathetic and parasympathetic systems, the transmission of efferent impulses from the pre- to the postganglionic neuron is mediated by acetylcholine. At postganglionic junctions the transmitter substances vary, with norepinephrine being released at the nerve endings of the sympathetic neuron and acetylcholine at the nerve endings of the parasympathetic (Fig. 6). The terms adrenergic and cholinergic are commonly used to characterize the actions of pharmacologic agents. Thus, a cholinergic agent produces an effect similar to that associated with the liberation of acetylcholine from the nerves, whereas an adrenergic agent mimics the effect of norepinephrine release.