What are the mydriatic (pupil dilating) drops used for dilatation of pupils?

Mydriatic Eye Drops for Pupil Dilation

The primary mydriatic drops used for pupil dilation are tropicamide (0.5% or 1%), phenylephrine (2.5% or 10%), and cyclopentolate (0.2-1%), with combination therapy providing superior and more stable dilation than single agents. 1, 2, 3

First-Line Agents

Tropicamide

• Tropicamide is an anticholinergic agent that blocks the iris sphincter muscle and ciliary muscle, producing mydriasis within 15-30 minutes with duration of 3-8 hours. 2
• The 1% concentration also paralyzes accommodation (cycloplegia), while 0.5% produces mydriasis with minimal cycloplegia. 2
• Heavily pigmented irides require higher doses or repeated applications compared to lightly pigmented irides. 2
• The American Academy of Ophthalmology notes that tropicamide provides adequate dilation with shorter duration compared to other cycloplegic agents, making it more convenient for adult patients. 4

Phenylephrine

• Phenylephrine hydrochloride (2.5% or 10%) is an alpha-adrenergic agonist specifically indicated for pupil dilation. 1
• Pupil movement begins within 15 minutes, with maximal mydriasis between 20-90 minutes and recovery after 3-8 hours. 1
• Darker irides dilate slower than lighter irides. 1
• Phenylephrine has no cycloplegic effect but provides pure mydriasis. 3

Cyclopentolate

• Cyclopentolate hydrochloride 1% produces rapid cycloplegia approximating atropine's effect but with shorter duration. 3
• For children under 6 months, cyclopentolate 0.2% combined with phenylephrine 1% is commonly used. 3
• In heavily pigmented irides, repeat dosing or adjunctive agents may be necessary. 3

Combination Therapy

Combining a muscarinic antagonist (tropicamide or cyclopentolate) with an alpha-adrenergic agonist (phenylephrine) produces superior and more stable mydriasis than either agent alone. 5, 6

Recommended Combinations:

• Tropicamide 0.5% or 1% with phenylephrine 2.5% produces approximately 7mm pupillary dilation within 60 minutes. 6
• Cyclopentolate 0.5% with phenylephrine 2.5% achieves similar dilation. 6
• Prior instillation of topical anesthetic (proparacaine 0.5%) reduces stinging, promotes penetration, and adds approximately 1mm additional dilation. 6, 3

Critical Safety Considerations

Angle-Closure Glaucoma Risk

• Mydriatic agents can precipitate acute angle-closure glaucoma in patients with narrow iridocorneal angles. 3, 4, 7
• For patients with suspected primary angle-closure disease, cautious dilation should only be performed when essential (e.g., suspected retinal pathology), and patients must be warned about symptoms until iridotomy is performed. 3
• Once iridotomy is completed, dilated examination can be safely performed. 3

Systemic Side Effects

• Uncommon systemic effects include fever, dry mouth, tachycardia, nausea, vomiting, flushing, somnolence, and rarely behavioral changes (delirium). 3, 4, 7
• These effects are more common in pediatric patients. 3, 4
• Punctal occlusion during and after instillation reduces systemic absorption and minimizes side effects. 3, 4

Pediatric Dosing Adjustments

• Dose should be determined based on child's weight, iris color, and dilation history. 3
• Using microdrops (approximately 5-6 microliters versus standard 35 microliters) achieves equivalent mydriasis with significantly reduced systemic side effects and faster visual recovery. 8, 9

Special Populations

Cardiovascular Disease

• Tropicamide is preferred over other mydriatic agents in patients with cardiovascular disease due to fewer systemic cardiovascular effects. 4

Infants and Preterm Neonates

• When strict precautions to prevent systemic absorption are applied (punctal occlusion, microdrops), mydriatic drops show no significant early hemodynamic effects on vital signs, cerebral/mesenteric perfusion, or cardiac function. 10

Atropine for Maximal Cycloplegia

• In rare cases requiring maximal cycloplegia, topical atropine sulfate 1% may be necessary, though it has prolonged duration of action. 3