Which drug dilates the pupil without affecting accommodation?

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Prepare for the Certified Paraoptometric Assistant (CPOA) Exam. Study with extensive flashcards and multiple choice questions with explanations. Enhance your skills and knowledge to succeed.

Multiple Choice

Which drug dilates the pupil without affecting accommodation?

Explanation:
Pupil dilation can occur by activating the iris dilator muscle without changing the muscles that control accommodation. Phenylephrine does exactly that: it stimulates alpha-1 receptors in the radial iris muscle, widening the pupil, and it doesn’t interfere with the ciliary muscle or sphincter pupillae. So accommodation remains unchanged. The other drugs are antimuscarinics that block parasympathetic control of both the iris sphincter and the ciliary muscle, causing both dilation and cycloplegia (loss of accommodation). That’s why they affect accommodation, unlike phenylephrine.

Pupil dilation can occur by activating the iris dilator muscle without changing the muscles that control accommodation. Phenylephrine does exactly that: it stimulates alpha-1 receptors in the radial iris muscle, widening the pupil, and it doesn’t interfere with the ciliary muscle or sphincter pupillae. So accommodation remains unchanged. The other drugs are antimuscarinics that block parasympathetic control of both the iris sphincter and the ciliary muscle, causing both dilation and cycloplegia (loss of accommodation). That’s why they affect accommodation, unlike phenylephrine.

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