Mydriatics and cycloplegics: Nursing pharmacology

Mydriatics and cycloplegics are a group of medications that have various indications for use in ophthalmology, such as during eye exams or ophthalmic surgical procedures.

Mydriatics cause mydriasis, or pupil dilation; whereas cycloplegics cause cycloplegia, or paralysis of the muscles that are responsible for accommodation to focus on nearby objects.

Commonly used mydriatics include adrenergic agonist medications, such as epinephrine and phenylephrine, while some medications that act as both mydriatics and cycloplegics include antimuscarinic medications, such as atropine, cyclopentolate, homatropine, scopolamine, and tropicamide.

These medications are applied topically in the form of eye drops, or ophthalmic ointments. Once applied, these medications work by blocking acetylcholine from binding to cholinergic receptors.

Mydriatic effects can involve stimulation of the iris dilator muscle, which dilates the pupil; or inhibition of the iris sphincter muscle, which constricts the pupil, or both.

On the other hand, cycloplegic effects result in paralysis of the ciliary muscle of the eye, leading to a loss of accommodation of the lens to focus on nearby objects.

Unfortunately, mydriatics and cycloplegics can result in side effects, such as dry eyes, blurred vision, and photophobia. Less frequently, they might be absorbed systemically, and clients may experience confusion and drowsiness, as well as dry mouth, flushing, tachycardia, hypertension, and constipation.