Mydriatics and cycloplegics
Eye drops that widen the pupil and relax focusing, for eye examinations. Antimuscarinic drops do both; phenylephrine only widens the pupil.
What they are
Antimuscarinic eye drops (tropicamide, cyclopentolate, atropine, homatropine) dilate the pupil (mydriasis) and paralyse accommodation (cycloplegia). They differ mainly in strength and how long they last.
Mechanism of action
By blocking muscarinic receptors they stop acetylcholine from contracting the iris sphincter and the ciliary muscle. The pupil widens and near focus is lost until the drug wears off.
Target: Muscarinic receptors of the iris sphincter and ciliary muscle
Drugs in this class
- TropicamideA short-acting antimuscarinic eye drop that widens the pupil for eye examinations. The effect wears off within the day.Muscarinic acetylcholine receptors of the iris sphincter and ciliary muscle
- CyclopentolateAn antimuscarinic eye drop that paralyses focusing and dilates the pupil, used to measure refraction. Stronger and…Muscarinic acetylcholine receptors of the iris sphincter and ciliary muscle
Others in the class
- Atropine (eye drops)
- Homatropine
- Phenylephrine (mydriatic only)
Test yourself
Think of the answer, then tap the question to see it.
What is the difference between mydriasis and cycloplegia?
Mydriasis is a wide pupil; cycloplegia is paralysis of the ciliary muscle (loss of accommodation).
Which drop dilates the pupil without cycloplegia?
Phenylephrine, an α1 agonist that contracts the iris dilator.
Why are antimuscarinic drops risky in small children?
Systemic absorption can cause central nervous system toxicity and a fast pulse.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - TROPICAMIDE solution/ drops (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - CYCLOPENTOLATE HYDROCHLORIDE solution/ drops (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.