A 66-year-old hypermetropic woman with shallow anterior chambers undergoes dilated fundus examination before cataract surgery. Two hours later she develops severe ocular pain and blurred vision in one eye. Which agent used during the examination most likely precipitated this event?

• A Proparacaine drops used for surface anaesthesia
• B Povidone-iodine drop used for conjunctival antisepsis
• C Fluorescein strip used for tear film staining
• D Tropicamide drops used for mydriasis ✓

Explanation

Mydriatics such as tropicamide can precipitate an attack of primary angle closure in predisposed eyes with crowded anterior segments, typically hypermetropic eyes with shallow chambers, because pupil dilation bunches the iris against the lens and increases relative pupillary block. Anaesthetics, fluorescein and povidone-iodine do not alter pupil size or angle dynamics and cannot trigger closure. This is why dilatation is performed cautiously in eyes with narrow angles.

Reference: Parsons' Diseases of the Eye, 23rd ed.

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Written and medically reviewed by the StethoPrep medical team.