cycloplegia

Cycloplegia is temporary paralysis of the ciliary muscle, which blocks accommodation. Topical muscarinic antagonists such as atropine, cyclopentolate, and tropicamide produce cycloplegia by binding to and blocking the muscarinic receptors of the ciliary muscle and the iris, so the pupil dilates as well.¹

Cycloplegic refraction measures refractive error in the absence of accommodation. Indications include suspected latent hyperopia, accommodative strabismus, any strabismus in a child, suspected amblyopia, and accommodative spasm, and the procedure is used most often in children. Cyclopentolate 1.0% is the routine agent above the age of 2 years, and atropine 0.5% or 1.0% is used when absolute cycloplegia is needed, as in preschool children with accommodative esotropia.²

The cycloplegic result is usually not prescribed as measured.³ Cycloplegia produces a complete relaxation of accommodation that the eye never reaches in its natural state, and a patient who keeps some accommodative tone after the drops wear off would likely find the full cycloplegic correction uncomfortable.⁴ The cycloplegic refraction instead establishes the baseline refractive state, for example in a young patient with suspected accommodative spasm or before refractive surgery.³