Which of the following is a carbonic anhydrase inhibitor used to lower IOP?

• A. Brimonidine 0.1%
• B. Latanoprost 0.005%
• C. Timolol 0.5%
• D. Dorzolamide

Answer: (D)

Reducing aqueous humor formation by blocking carbonic anhydrase in the ciliary processes is how this class lowers intraocular pressure. By inhibiting carbonic anhydrase, less bicarbonate is produced, which reduces ion transport and water movement into the eye, leading to less aqueous humor production. Dorzolamide is a topical carbonic anhydrase inhibitor used to lower IOP, making it the correct choice.

Brimonidine lowers IOP mainly by decreasing aqueous production and modestly increasing uveoscleral outflow via an alpha-2 adrenergic mechanism. Latanoprost lowers IOP by increasing outflow through the uveoscleral pathway as a prostaglandin analog. Timolol lowers IOP by reducing aqueous humor production as a nonselective beta-blocker.