Which drug is a commonly used first-line topical therapy to lower intraocular pressure in canine glaucoma?

• A. Timolol
• B. Prednisolone
• C. Atropine
• D. Latanoprost

Answer: (A)

Reducing the production of aqueous humor lowers intraocular pressure, and topical beta-blockers achieve this by blocking beta-adrenergic receptors in the ciliary body. Timolol, a nonselective beta-blocker, is commonly used as a first-line topical therapy in canine glaucoma because it reliably decreases aqueous humor formation, leading to meaningful IO pressure reduction. It’s effective, has minimal systemic effects when applied topically, and is easy to administer, making it a practical initial choice.

Prednisolone is a corticosteroid that can raise intraocular pressure in susceptible eyes, so it’s not used for glaucoma management. Atropine dilates the pupil and can worsen angle-closure risk, so it’s contraindicated. Latanoprost, a prostaglandin analog, lowers IOP by increasing outflow, and is a valid option, but timolol is typically encountered as the standard first-line topical therapy in many canine glaucoma protocols due to its established efficacy and safety profile.