A 62-year-old woman from Mumbai with recently diagnosed primary open-angle glaucoma (open angles confirmed on gonioscopy, IOP 26 mmHg, early glaucomatous visual field defect) has been started on topical timolol 0.5% twice daily. After 4 weeks, IOP remains 24 mmHg in both eyes. Visual fields show no progression. She tolerates the medication well with no systemic side effects. What is the most appropriate next step in management?

Explanation

## Clinical Scenario Patient with confirmed POAG on **monotherapy (timolol)** with **inadequate IOP control** (target typically < 18 mmHg for early disease with VF loss). The medication is well-tolerated, so the next step is **escalation of medical therapy** before considering laser or surgery. ## Rationale for Adding Prostaglandin Analogue **Key Point:** In POAG, when **monotherapy fails to reach target IOP**, the standard next step is **addition of a second agent** from a different drug class, not switching or increasing concentration. **High-Yield:** Medical therapy escalation follows a stepwise pattern: 1. **Monotherapy** (first-line: PGA, beta-blocker, CAI, or alpha-agonist) 2. **Dual therapy** (add agent from different class) 3. **Triple therapy** (add third agent) 4. **Laser trabeculoplasty** (if medical therapy insufficient) 5. **Glaucoma surgery** (if laser fails) ## Why Prostaglandin Analogue? | Agent Class | Mechanism | Efficacy | Typical IOP Reduction | |-------------|-----------|----------|----------------------| | **Prostaglandin analogue** | ↑ Uveoscleral outflow | **Highest** | 25–35% | | Beta-blocker (timolol) | ↓ Aqueous production | Moderate | 20–25% | | CAI | ↓ Aqueous production | Moderate | 15–20% | | Alpha-agonist | ↓ Production + ↑ outflow | Moderate | 15–20% | **Clinical Pearl:** PGAs are the **most potent topical agents** and are preferred as the **second agent** when monotherapy fails. They also have **once-daily dosing** (better compliance) and **no systemic side effects** in this patient. ## Why Other Options Are Suboptimal ```mermaid flowchart TD A[POAG on monotherapy<br/>IOP inadequately controlled]:::outcome A --> B{Medication tolerated?}:::decision B -->|Yes| C[Add second agent<br/>from different class]:::action B -->|No| D[Switch to different<br/>monotherapy]:::action C --> E[PGA is first choice<br/>for second agent]:::action E --> F{IOP at target?}:::decision F -->|Yes| G[Continue dual therapy]:::outcome F -->|No| H[Add third agent<br/>or consider laser]:::action D --> I[Reassess after 4 weeks]:::action ``` **Mnemonic: POAG Medical Escalation — MAL:** - **M**onotherapy first (PGA, BB, CAI, or alpha-agonist) - **A**dd second agent (different class) if inadequate control - **L**aser/surgery if medical therapy fails **Warning:** Increasing timolol concentration from 0.5% to 0.25% is **backwards** — concentrations are already optimized. Adding a complementary agent is the correct approach.