Tropicamide

Tropicamide, which is to some extent structurally related to atropine, induces mydriasis and cycloplegia through paralysis of the parasympathetic system. Tropicamide is a parasympatholytic agent, which acts by blocking the action of the parasympathetic nervous system. As acetylcholine is the neurotransmitter at the receptor site of the parasympathetic nervous system, tropicamide competes with acetylcholine for uptake at the receptor sites, thereby blocking its action. The results are mydriasis, due to unopposed action of the dilator pupillae, and cycloplegia.Tropicamide visibly dilates the pupil after 5 minutes. It reaches its maximum diameter after 20-25 minutes and returns to its normal size within approx. 6 hours. The onset of the effect is rapid, but it disappears 45-60 minutes after the last instillation. The best time for retinoscopy is therefore approximately 20 minutes after the instillation of the last drop.