Which anticholinergic medication has the longest cycloplegic effect?

Atropine is recognized for having the longest duration of cycloplegic effect among the anticholinergic medications listed. It works by blocking the action of acetylcholine on the muscarinic receptors in the eye, leading to prolonged paralysis of the ciliary muscle, which is responsible for accommodation, as well as dilation of the pupil.

The prolonged effect of atropine can last from several days up to two weeks, making it particularly effective in situations where extended cycloplegia is desired, such as in the treatment of amblyopia or for fundus examinations in patients with specific conditions. This extended duration is significant in clinical practice, especially for young patients or cases where precise optical measurements are essential.

In comparison, other anticholinergics such as scopolamine, homatropine, and cyclopentolate have shorter durations of action. Scopolamine is primarily used for motion sickness and has limited applicability in cycloplegia. Homatropine typically provides a cycloplegic effect for about 1-3 days, while cyclopentolate's effects generally last for a few hours to a day. This clear distinction in duration underscores why atropine is the preferred choice when a long-acting cycloplegic agent