Glaucoma
Glaucoma is examined as a progressive optic neuropathy with pressure as a risk factor, not as a number. Expect questions on angle assessment, perimetric interpretation and the order of treatment in acute angle closure.
Definitions and diagnosis
Glaucoma means retinal ganglion cell loss with characteristic disc changes (rim thinning, cupping, disc haemorrhage, nerve fibre layer defect) and corresponding field loss. Pressure is the only modifiable risk factor, but normal-tension glaucoma exists. Open-angle glaucoma is painless; acute angle closure is painful with a mid-dilated pupil, corneal oedema and pressure often above 40 mmHg. Gonioscopy defines the angle, and a convex iris profile suggests appositional closure.
Treatment ladder
Prostaglandin analogues lower pressure most and are first-line in open-angle glaucoma. Beta-blockers are contraindicated in asthma and heart block; alpha-agonists cause follicular conjunctivitis; carbonic anhydrase inhibitors cause paraesthesia and are avoided in sickle cell disease and sulfonamide allergy. Selective laser trabeculoplasty is increasingly first-line. Surgery means trabeculectomy with mitomycin C, tube shunts after failed surgery, and microinvasive glaucoma surgery at the time of cataract surgery.
Acute angle closure
Lower the pressure medically with a topical beta-blocker, alpha-agonist, pilocarpine, systemic acetazolamide and an osmotic agent, then perform laser peripheral iridotomy in both eyes because the fellow eye is at risk. Primary lens extraction is increasingly preferred as definitive treatment.
Monitoring
Fields and OCT nerve fibre layer are read together; progression is judged on trend, not a single field, and target pressure is individualised by stage and life expectancy.
Worked example
A 70-year-old has a painful red eye, a fixed mid-dilated pupil, hazy cornea, pressure 52 mmHg and nausea. Reasoning: this is acute angle closure. Start medical treatment, arrange laser iridotomy as soon as the cornea clears, treat the fellow eye prophylactically, and do not simply repeat drops at review.
Traps
Diagnosing glaucoma from cupping without a field; forgetting the fellow eye in angle closure; using topical steroid without monitoring the pressure response; assuming a normal pressure excludes glaucoma.