Anti-Glaucoma Drugs: Current Practice
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Direct answer
One night-time drop of latanoprost 0.005% lowers intraocular pressure by roughly a quarter by opening the uveoscleral outflow pathway — and that single fact reordered glaucoma therapy, making prostaglandin analogues the first line and reducing timolol to second choice. Beta-blockers, alpha-2 agonists and topical carbonic anhydrase inhibitors all cut aqueous humour production instead. In acute angle closure the sequence reverses everything: acetazolamide systemically, multiple topical agents, pilocarpine only once the pressure begins to fall, mannitol if severe, and laser peripheral iridotomy as the definitive act. Because eye drops drain through the nasolacrimal duct into the nose, they behave like systemic drugs — timolol can kill an asthmatic.
What you must remember
- Prostaglandin analogues (first line): latanoprost 0.005%, travoprost, bimatoprost, tafluprost — once at night; iris hyperpigmentation, lash hypertrichosis, periocular fat atrophy (enophthalmos), and uveitis or herpetic keratitis reactivation.
- Timolol 0.25/0.5%: reduces aqueous production; contraindicated in asthma, heart block, bradycardia, decompensated heart failure; masks hypoglycaemia awareness in insulin-treated diabetics.
- Brimonidine 0.2%: cuts production and boosts uveoscleral outflow; avoid in infants under 2 years (apnoea risk); chronic use brings allergic follicular conjunctivitis.
- Dorzolamide 2% TID and oral/IV acetazolamide: carbonic anhydrase inhibition; topical gives bitter taste and punctate keratopathy, oral gives paraesthesiae and metabolic acidosis; sulphonamide cross-allergy caution.
- Pilocarpine 2–4%: miotic pulling the peripheral iris from the angle; ciliary spasm and brow ache; useless at very high IOP where the sphincter is ischaemic — it works only after the pressure drops.
- Acute angle closure sequence: acetazolamide IV/oral plus topical timolol and brimonidine; add pilocarpine once IOP is falling; mannitol 1–2 g/kg IV for refractory pressure; topical steroid for inflammation; definitive — laser peripheral iridotomy in both eyes.
- NLEM anchor: timolol and latanoprost appear on India's NLEM 2022, and acetazolamide systemically — generic access is broad.
- Technique that matters: punctum occlusion and closed-eye lid closure for a minute after each drop halve systemic absorption.
Working through an acute angle-closure attack
A 55-year-old woman presents with a red, painful eye, blurred vision with halos, vomiting, and a mid-dilated unreactive pupil on a hard globe — the examination confirms raised IOP and a closed angle. Step one is systemic and topical pressure-cutting: acetazolamide 500 mg IV or orally, timolol 0.5%, brimonidine. Step two is patience with pilocarpine: at 50 mmHg the iris sphincter is ischaemic and will not respond, so the miotic goes in once the pressure is clearly falling, after which it pulls the peripheral iris out of the angle. Step three treats inflammation with topical steroid, and step four is mannitol if the pressure remains high. Once quiet, laser peripheral iridotomy is done — in both eyes, because the fellow eye shares the anatomy and is the next attack waiting to happen. Reading the sequence backwards — pilocarpine first — is the classic case-writing error.
Where students slip
The recurring slip is treating eye drops as local therapy. Timolol's systemic absorption through the nasolacrimal route produces genuine bronchospasm, bradycardia and heart block — deaths have followed "harmless" glaucoma drops in asthmatics — hence punctal occlusion technique in every counselling. The second slip is pharmacodynamic: prostaglandin analogues increase outflow, while beta-blockers, alpha-2 agonists and CAIs suppress production; combination drops pair one of each on purpose. Third, the cosmetic effects of latanoprost — darkened irides, longer lashes, deepened upper lid sulcus — are not trivia but adherence conversations, because a patient who stops a drop silently is more dangerous than one who never started. And in the acute attack, ordering pilocarpine before the pressure is falling simply documents an ischaemic sphincter doing nothing.
Frequently asked questions
Why is latanoprost now first line in open-angle glaucoma?
Once-nightly dosing, no systemic cardiopulmonary contraindications, and pressure lowering comparable to or better than timolol.
What are the classic side effects of prostaglandin analogues?
Iris darkening, eyelash hypertrichosis, periocular fat atrophy, conjunctival hyperaemia, and reactivation of uveitis or herpes keratitis.
Why must timolol be avoided in asthma?
Nasolacrimal drainage delivers systemic beta-blockade capable of precipitating severe bronchospasm and bradycardia.
When does pilocarpine work in acute angle closure?
Only after medical therapy has begun lowering IOP — the ischaemic sphincter will not respond at very high pressures.
What is the definitive treatment of primary angle closure?
Laser peripheral iridotomy, performed in both eyes to relieve pupillary block permanently.