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Glaucomas Consider the preservative in eye drops as some, especially benzalkonium chloride, can irritate and damage the cornea and may cause symptoms similar to those of dry eye syndrome. These may improve after swapping to less irritant or preservative-free products. See also Preservatives p 461. Acetazolamide may be used if topical treatment, laser or surgical interventions are not possible or have poor outcomes. See also www.nhmrc.gov.au/guidelines/publications/ cp113-cp113b Glaucomas are characterised by optic neuropathy, optic disc changes and irreversible, progressive visual field loss. They are primarily classified as either open-angle or angle-closure. Open-angle glaucoma Increased intraocular pressure (IOP) or ocular hypertension (although not a defining characteristic) is the only modifiable risk factor for glaucoma. Though not all people with raised IOP will develop glaucoma, it is more likely in those with major risk factors, such as older age, strong family history. Early treatment preserves the visual field and reduces rate of glaucoma progression whether or not IOP is raised. A target IOP for treatment is determined based upon the patient’s risk factors for glaucoma progression, the amount of initial damage and the rate of deterioration. Laser or surgical interventions are considered if drug treatment is inadequate or intolerable. Practice points • assess treatment by monitoring changes in visual field and optic disc appearance • a leaflet on eye drop administration is available from Glaucoma Australia at www.glaucoma.org.au/ eyedrops.htm (see also Counselling p 461) Angle-closure glaucoma Up to 75% of patients with angle-closure glaucoma will have intermittent or chronic angle closure with asymptomatic progressive loss of visual field rather than an acute crisis. Initial treatment is iridotomy (laser or surgical); if unsuccessful, surgical procedures are considered. Topical treatment may be used, particularly in those with persistent raised IOP despite laser or surgical procedures. Rationale for drug use Prevent progressive loss of vision by lowering IOP. Drug choice See also Table 11–1 Comparison of topical drugs for open-angle glaucoma p 461 Risk factors for angle-closure glaucoma Risk factors include Asian ethnicity, small eye, narrow angle of anterior chamber, shallow anterior chamber, long sight, age and female gender. Use of some drugs may precipitate acute angle-closure crisis. Topical drugs are first-line treatment (either alone or in combination). They reduce IOP by decreasing production of aqueous humour and/or by increasing its outflow. Consider starting, changing or adding medications to just one eye, using the other as a control; assess IOP within 2–4 weeks before treating the other eye. Since glaucoma is usually asymptomatic, compliance is a major problem (up to 50% of patients fail to use their medication correctly); check compliance when considering changing dose or adding a new agent to an existing regimen. Acute angle-closure crisis This is a rare ophthalmic emergency: treatment is by laser iridotomy. Oral, IV and topical medication may be necessary to stabilise the eye and lower IOP before laser iridotomy. IV acetazolamide, topical pilocarpine, a topical beta-blocker, IV mannitol or oral glycerol may be used; seek specialist advice. Table 11–1 Comparison of topical drugs for open-angle glaucoma Class Doses per day Comments prostaglandin analogues (bimatoprost, latanoprost, tafluprost, travoprost) 1 • • • • first line increase aqueous outflow the most effective class may cause iris hyperpigmentation and eyelash changes beta-blockers (betaxolol, timolol) 1–2 • • • • first line decrease aqueous production may cause systemic adverse effects, eg bradycardia generally avoided in severe or poorly controlled asthma alpha2 agonists (apraclonidine, brimonidine) 2–3 • second line • increase aqueous outflow and decrease its production • apraclonidine can only be used short term carbonic anhydrase inhibitors (brinzolamide, dorzolamide) 2–3 • second line • decrease aqueous production cholinergic (pilocarpine) 3–4 • rarely used (eg angle-closure glaucoma and some secondary glaucomas), seek specialist advice • increases aqueous outflow • high incidence of adverse effects, eg blurred vision, headache AMH © 2014 www.amh.net.au