Certified Ophthalmic Medical Technologist (COMT) Practice Exam

How do all parasympathomimetics decrease intraocular pressure?

1. By inhibiting aqueous humor production

2. By increasing blood flow to the eye

3. By increasing the outflow of aqueous humor

4. By constricting the pupil

The correct answer is: By increasing the outflow of aqueous humor

Parasympathomimetics, also known as cholinergic agents, primarily lower intraocular pressure by enhancing the outflow of aqueous humor. These agents stimulate the muscarinic receptors in the eye, leading to contraction of the ciliary muscle. This contraction not only changes the configuration of the trabecular meshwork but also opens the canal of Schlemm, facilitating improved drainage of aqueous humor from the anterior chamber into the systemic circulation. Increasing aqueous humor outflow directly addresses the mechanisms that contribute to elevated intraocular pressure, which is a key factor in conditions like glaucoma. In contrast, the other options do not adequately explain the primary mechanism of action of parasympathomimetics in reducing intraocular pressure. While constricting the pupil can be a secondary effect of these agents, it is not the most direct manner in which they lower pressure. Similarly, increasing blood flow or inhibiting aqueous humor production is not a primary action associated with parasympathomimetics, further underscoring why enhancing aqueous humor outflow is the correct answer.