Which drug reduces intraocular pressure by decreasing the formation of the aqueous humor?
A. Timololb.B. Behothiophate
C. Pilocarpine
D. Isofluorphate
The answer is A.
When applied topically to the eye, both the direct-
acting cholinomimetic agents (e.g., pilocarpifle) and those cholinomimctic
drugs that act by inhibition of AChE (e.g.. echothiophate, isofluorphate. and
physostigmine) cause miosis by contracting the sphincter muscle of the iris and
reducing ocular pressure by contracting the ciliary muscle. In patients with
glaucoma, this latter effect permits greater drainage of the aqueous humor
through the trabecular meshwork in the canal of Schlemm and a reduction in
resistance to outflow of the aqueous humor. Certain β-adrenergic blocking agents
(e.g., timololand levobunolol) applied to the eye are also very useful in
treating chronic wide-angle glaucoma. These drugs appear to act by decreasing
the secretion (or formation) of the aqueous humor by antagonizing the effect of
circulating catecholamines on 13- β-adrenergic receptors in the ciliary
epithelium.
