What are the drugs that cause pupillary dilation and restrict accommodation?

Drugs That Cause Pupillary Dilation and Restrict Accommodation

Anticholinergic medications are the primary drug class that causes both pupillary dilation (mydriasis) and restriction of accommodation (cycloplegia) by blocking the parasympathetic muscarinic receptors in the eye. 1

Mechanism of Action

• Anticholinergic agents act as competitive antagonists of the parasympathetic acetylcholine muscarinic receptors, inducing mydriasis by inhibiting contraction of the circular pupillary sphincter muscle and allowing the radial pupillary dilator muscle to contract 1
• These drugs simultaneously induce cycloplegia by paralyzing the ciliary muscle that controls accommodation while viewing objects 1

Specific Anticholinergic Agents

Atropine

• Produces strong mydriasis and cycloplegia with prolonged duration of action 1
• Maximum effect for mydriasis achieved in 30-40 minutes with recovery after approximately 7-10 days 1
• Maximum effect for cycloplegia achieved within 60-180 minutes with recovery after approximately 7-12 days 1
• Side effects include blurry vision, light sensitivity, and potential systemic effects (dry mouth, tachycardia) 1

Cyclopentolate

• Acts rapidly but has shorter duration than atropine 2
• Maximal cycloplegia occurs within 25-75 minutes after instillation 2
• Complete recovery of accommodation usually takes 6-24 hours 2
• Complete recovery from mydriasis may require several days in some individuals 2
• Heavily pigmented irides may require more doses than lightly pigmented irides 2

Tropicamide

• Shorter-acting anticholinergic agent compared to atropine and cyclopentolate 3
• Often used in combination with phenylephrine for diagnostic pupil dilation 3
• Has less effect on accommodation than atropine or cyclopentolate 3

Scopolamine

• Centrally acting anticholinergic that can suppress acute vertigo attacks but also causes pupillary dilation 4
• Most commonly used in a transdermal formulation primarily for motion sickness 4
• Can cause blurring of vision, dry mouth, dilated pupils, urinary retention, and sedation 4

Homatropine

• Intermediate duration of action between tropicamide and atropine 5
• Produces significant mydriasis and cycloplegia 5

Other Drugs That Cause Pupillary Dilation

• Phenylephrine: An adrenergic agent that causes mydriasis without significant cycloplegia by stimulating the dilator muscle of the iris 3
• Anticholinergic medications used systemically (not just ophthalmic formulations) can cause pupillary dilation, including:
  • Tricyclic antidepressants 6
  • Antihistamines 6
  • Central nervous system stimulants such as cocaine, methylphenidate, and amphetamines 6

Clinical Applications

• Cycloplegic refraction: Adequate cycloplegia is necessary for accurate retinoscopic refraction in children because of their increased accommodation compared with adults 4
• Funduscopic examination: Pupillary dilation facilitates examination of the optic disc, macula, retina, vessels, and choroid 4
• Treatment of uveitis: Anticholinergic agents help prevent posterior synechiae formation and provide pain relief by relaxing the ciliary muscle 5

Concentration Effects and Side Effects

• Lower concentrations of atropine (0.02%) can provide clinical benefits with fewer side effects compared to higher concentrations (1%) 7
• At 0.02% concentration, mean pupillary dilation is approximately 3 mm with mean accommodative amplitude of 8 diopters, which doesn't produce significant clinical symptoms 7
• Side effects of anticholinergic agents include:
  • Local: blurred vision, photophobia, increased intraocular pressure in susceptible individuals 1
  • Systemic (especially with higher concentrations): fever, dry mouth, rapid pulse, nausea, vomiting, flushing, somnolence, and rarely behavioral changes 4

Cautions and Contraindications

• Anticholinergic agents can precipitate acute angle-closure glaucoma in susceptible individuals with narrow iridocorneal angles 8
• Patients with primary angle-closure suspect (PACS) should be warned that anticholinergic medications could cause pupil dilation and induce acute angle-closure 4
• Patients should be advised not to drive or engage in hazardous activities while pupils are dilated 1
• Patients should be informed that they may experience blurry vision and sensitivity to light during dilation 1

Duration of Effects

• Tropicamide: Shortest duration (4-6 hours) 3, 5
• Cyclopentolate: Intermediate duration (6-24 hours) 2
• Atropine: Longest duration (7-12 days) 1