cycloplegic

A cycloplegic is a medication used in ophthalmology to induce cycloplegia, the paralysis of the ciliary muscle, which also causes pupil dilation (mydriasis). By blocking the parasympathetic input to the eye, cycloplegics inhibit accommodation and relax the focusing muscles, facilitating certain eye examinations and procedures and improving accuracy in refractive assessment.

Cycloplegia works by antagonizing muscarinic acetylcholine receptors in the iris sphincter and ciliary body. This inhibition reduces the eye’s ability to accommodate and enlarges the pupil, allowing clinicians to view the internal structures without the interference of accommodation or constriction. The onset and duration of effect vary by agent, with some providing rapid, short-term dilation and others producing longer-lasting paralysis.

Indications for cycloplegics include cycloplegic refraction, especially in children, to obtain an accurate measure of refractive error; examination of the posterior segment when accommodation could hinder assessment; and certain inflammatory or diagnostic situations where pupil dilation is required. They may also be used preoperatively or in the management of certain painful uveitic conditions to reduce ciliary spasm.

Common agents include atropine, scopolamine (hyoscine), cyclopentolate, tropicamide, and homatropine. Responsiveness and duration vary: atropine is long-acting (days to weeks); cyclopentolate provides intermediate duration (about 24 hours); tropicamide is short-acting (several hours). Careful dosing and monitoring are essential, as systemic anticholinergic effects can occur (dry mouth, flushing, tachycardia, confusion) and there are contraindications, such as shallow anterior chambers or narrow-angle glaucoma.

Safety considerations include avoiding use in patients with known glaucoma risk, informing about transient light sensitivity, and advising against driving until effects wear off.