Timolol's topical use for glaucoma is due to which effect?

• A. Increases intraocular pressure
• B. Pupillary dilation
• C. Decreases aqueous humor production
• D. Increases aqueous humor drainage

Answer: (C)

Timolol lowers intraocular pressure by blocking beta-adrenergic receptors in the ciliary body, which reduces aqueous humor production. Since intraocular pressure largely depends on how much aqueous humor the ciliary epithelium makes, cutting production lowers pressure. The effect comes from decreased cAMP signaling in the ciliary tissues after beta blockade, not from changing drainage or causing pupil dilation. So topical timolol helps glaucoma by reducing the amount of fluid produced, rather than increasing outflow.