How do anticholinergic drugs affect the pupils of the eye?

Anticholinergic drugs primarily work by blocking the action of acetylcholine at muscarinic receptors within the eye, which leads to pupil dilation, a process known as mydriasis. Specifically, these agents relax the sphincter muscle of the iris, preventing it from constricting the pupil. This dilation effect is significant in various clinical settings, including during eye examinations, where enhanced visualization of the interior structures of the eye is desired.

In contrast, pupil constriction, known as miosis, typically results from cholinergic stimulation, not from anticholinergic activity. Thus, choices that suggest constriction or that there is no effect do not accurately represent the pharmacological action of these drugs. The notion that pupils could change color is not related to the mechanism of action of anticholinergic agents and does not correspond with established pharmacological principles.