How Do Cycloplegics/Mydriatics Work?

Reviewed on 5/13/2021

What are cycloplegics/mydriatics and how do they work?

Cycloplegics/mydriatics are ophthalmic medications that are used to dilate the pupil (mydriasis). Each cycloplegic/mydriatic drug works in a different way to maintain dilation in the pupil for a specified period. Cycloplegics/mydriatics work in the following ways to achieve mydriasis:

  • Paralyze the ciliary muscle (cycloplegia), which adjusts the lens shape and thickness to enable us to focus on near and far objects. The ability to focus at different distances is known as eye accommodation.
  • Paralyze the sphincter muscle which encircles the pupil and helps contract the pupil in bright light.
  • Activate contraction of the dilator (radial) muscle of the iris which dilates the pupil.

Some cycloplegics/mydriatics are anticholinergic. Ophthalmic anticholinergics block the activity of acetylcholine, a substance that activates the contraction of ciliary and sphincter muscles inside the eye, resulting in temporary paralysis of those muscles.

Acetylcholine is a neurotransmitter that motor nerve cells (neurons) in neuromuscular junctions release to activate muscles.

Other cycloplegics/mydriatics are alpha agonists that stimulate alpha adrenergic receptors and cause contraction of dilator muscles of the iris and constriction of blood vessels. Alpha adrenergic receptors are proteins that make smooth muscles contract in response to hormones (catecholamines) epinephrine and norepinephrine released by the adrenal gland.

Cycloplegics/mydriatics are often administered as combination drugs to achieve dilation of the pupil. Cycloplegic/mydriatic medications may be combined with an ophthalmic non-steroidal anti-inflammatory drug (NSAID) to prevent pain and inflammation from eye surgery.

How are cycloplegics/mydriatics used?

Cycloplegics/mydriatics are ophthalmic solutions or ointments topically administered in the eye. Cycloplegics/mydriatics are used for the following purposes:

  • Dilation of the pupils for diagnostic or surgical procedures
  • Treatment of eye redness
  • As part of the treatment for uveitis (inflammation of uvea, the middle layer of the eye) to:
    • Relieve pain by preventing movement of the iris
    • Prevent the iris from adhering to the lens (posterior synechiae)
    • Prevent further flare-up of uveitis
  • Cataract and intraocular lens replacement surgery

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What are side effects of cycloplegics/mydriatics?

Side effects of cycloplegic/mydriatic drugs may include the following:

Ocular side effects:

Systemic side effects:

Rare but severe side effects include:

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

What are names of some cycloplegic/mydriatic drugs?

Generic and brand names of some cycloplegic/mydriatic drugs include:

Anticholinergic agents:

Alpha adrenergic agonists:

Combination drugs

  • Anticholinergic/alpha agonist:
    • Cyclopentolate hydrochloride/phenylephrine hydrochloride (Cyclomydril)
  • Alpha agonist/anticholinergic:
    • Hydroxyamphetamine hydrobromide/tropicamide (Paremyd)
  • Ophthalmic NSAID/alpha agonist:
  • Anticholinergic/alpha agonist:
    • Tropicamide/phenylephrine hydrochloride (MydCombi) - Pending FDA approval

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References
https://reference.medscape.com/drugs/cycloplegics-mydriatics

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