cycloplegia

Cycloplegia is a state in which the ciliary muscle is temporarily paralyzed, resulting in loss of accommodation. In ophthalmology, the term most often refers to drug-induced paralysis of accommodation, usually accompanied by mydriasis (pupil dilation). Pathologic cycloplegia can occur with neurological injury affecting the oculomotor nerve or the ciliary ganglion.

Mechanism and causes: Pharmacologic cycloplegia is produced by antimuscarinic drugs that block acetylcholine signaling at muscarinic receptors in the ciliary muscle and iris sphincter. This prevents accommodation and reduces pupil constriction. Common agents include atropine (long-acting), homatropine and cyclopentolate (intermediate), and tropicamide (short-acting). Scopolamine is another antimuscarinic sometimes used. The effect can be desirable for certain clinical examinations and procedures.

Indications: It is routinely used in pediatric refraction to prevent accommodation and obtain accurate measurements, in the evaluation of latent hyperopia, and in strabismus assessment. It is also employed to relieve ciliary spasm in uveitis and to facilitate thorough ocular examination or surgical planning when dilation and loss of accommodation are beneficial.

Administration and duration: Eye drops are instilled as prescribed; duration depends on the agent (e.g., tropicamide 4–6 hours, cyclopentolate up to about 24 hours, atropine for several days). Dilation and blurred near vision follow, and patients are often advised to wear sunglasses and avoid activities requiring sharp near focus.

Side effects and precautions: Common adverse effects include blurred near vision, photophobia, and dry mouth. Systemic anticholinergic effects are possible, especially with potent agents. Contraindications include narrow-angle glaucoma and certain corneal or neurologic conditions; use with caution in the elderly or in patients with cardiac or CNS disease.