A patient with POAG on latanoprost monotherapy has an IOP of 22 mmHg. Target IOP is 14 mmHg. The next agent to add should reduce IOP by an additional 20–25%. Which combination is most rational pharmacologically given that latanoprost already maximises uveoscleral outflow?

• A Add another prostaglandin analogue (bimatoprost)
• B Add a topical beta-blocker (timolol) to reduce aqueous production ✓
• C Add a topical carbonic anhydrase inhibitor (dorzolamide) which increases uveoscleral flow
• D Add a topical alpha-2 agonist (brimonidine) which enhances trabecular outflow

Explanation

Combining a prostaglandin analogue (which maximises uveoscleral outflow) with a beta-blocker (which reduces aqueous production by ~25-30%) provides complementary mechanisms and is the most rational and evidence-based addition. Adding a second prostaglandin provides minimal additional effect (tachyphylaxis and same receptor saturation). Dorzolamide reduces aqueous production — it does not increase uveoscleral flow. Brimonidine reduces aqueous production and increases uveoscleral outflow, but the primary mechanism is production reduction rather than trabecular enhancement; it is a second-line addition after beta-blockers.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.