Parasympathetic Antagonists

Routine mydriasis to allow examination of the fundus is best achieved by tropicamide 0.5% or 1% drops because the effect lasts for only about 3 h. Cyclopentolate 1% (0.5% in babies) can last for 24 h, but because of its cycloplegic effect (blockade of accommodation) is preferable for the examination of children's eyes when refraction is also needed. Dilating the pupil runs the risk of inducing an attack of acute narrow-angle glaucoma in a predisposed individual. Because the vision could remain blurred, driving should be avoided within the first 6-8h after mydriasis. Atropine in drop form is a long-acting mydri-atic, which is used when it is necessary to prevent or break down adhesions between iris and lens in acute iritis (posterior synechiae). It is also used in the treatment of amblyopia in children. Its effect lasts for about seven days. Allergic reactions are quite common and occasionally systemic absorption can cause central nervous system symptoms of atropine toxicity.

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