Key Facts

Glaucoma is often called the "silent thief of sight" because it is typically asymptomatic until significant irreversible visual field loss has occurred. Early detection and treatment are essential.

Epidemiology

• ~700,000 affected in the UK; ~2% of >40s
• Leading cause of irreversible blindness worldwide
• 50% of cases remain undiagnosed
• Prevalence increases with age: 1% at 40, 5% at 80

Aetiology

• Primary open-angle glaucoma (POAG): open drainage angle; impaired trabecular meshwork outflow
• Primary angle-closure glaucoma (PACG): anatomically narrow angle; see separate topic for acute angle-closure
• Secondary: steroid-induced, uveitic, neovascular (proliferative diabetic retinopathy), pseudoexfoliation, pigment dispersion
• Congenital/developmental: rare; present in infancy with buphthalmos

Pathophysiology

• IOP determined by aqueous humour production (ciliary body) and drainage (trabecular meshwork → canal of Schlemm; or uveoscleral outflow)
• In POAG: increased resistance to outflow through trabecular meshwork
• Elevated IOP → mechanical compression of retinal ganglion cell axons at the lamina cribrosa → progressive axonal loss → optic disc cupping → visual field loss
• Vascular factors (reduced optic disc perfusion) also contribute, especially in normal-tension glaucoma

POAG

• Asymptomatic until advanced (peripheral vision lost first; central preserved until late)
• Detected at routine optometry: raised IOP, suspicious disc, field defect
• Bilateral but often asymmetric
• No pain or redness

Symptoms of Advanced Disease

• Tunnel vision
• Difficulty with mobility (bumping into things)
• Near-misses (driving)
• Eventually total blindness if untreated

Red Flags

• Rapid visual field loss (suspect secondary cause or poor compliance)
• Young patient with glaucoma (consider secondary causes, congenital)
• Unilateral raised IOP with inflammation (uveitic glaucoma)
• IOP >40mmHg (acute angle-closure or secondary cause)

Bedside

• Visual acuity
• IOP measurement: Goldmann applanation tonometry (gold standard); normal 10-21mmHg
• Gonioscopy: angle assessment (open vs closed)

Bloods

• Not routinely needed

Imaging

• OCT (optical coherence tomography): retinal nerve fibre layer (RNFL) thickness; detects early damage before visual field loss
• Visual field testing (Humphrey/standard automated perimetry): detects arcuate scotoma, nasal step
• Optic disc photography: baseline and serial monitoring

Special Tests

• Central corneal thickness (CCT): thin cornea (≤555μm) underestimates true IOP and is an independent risk factor
• Disc assessment: cup-to-disc ratio (CDR), neuroretinal rim, disc haemorrhage, RNFL defects
• 24-hour IOP profile: for normal-tension glaucoma
• Repeat visual fields for confirmation (learning effect in first test)

Non-pharmacological

• Patient education about chronic nature and importance of adherence
• Driving standards (DVLA): must have adequate binocular visual field

Pharmacological (NICE NG81)

• First-line: prostaglandin analogue — latanoprost 0.005% drops OD at night
  • Side effects: eyelash growth, iris pigmentation (permanent), periorbital fat atrophy
  • Alternatives: bimatoprost, travoprost, tafluprost
• Second-line (if PGA insufficient/not tolerated): add or switch to:
  • Beta-blocker: timolol 0.5% BD (avoid in asthma, heart block, bradycardia)
  • Carbonic anhydrase inhibitor: dorzolamide 2% TDS or brinzolamide 1% BD
  • Alpha-2 agonist: brimonidine 0.2% BD
• Combination drops: available for adherence (e.g. Cosopt = timolol + dorzolamide; Ganfort = bimatoprost + timolol)
• Maximum medical therapy: combination of 2-3 agents from different classes

Surgical/Interventional

• Selective laser trabeculoplasty (SLT): can be first-line alternative to drops (LiGHT trial); well-tolerated; repeatable
• Trabeculectomy: gold standard surgical treatment for uncontrolled glaucoma; creates fistula for aqueous drainage
• Tube shunt/drainage device: for complex or refractory glaucoma
• Minimally invasive glaucoma surgery (MIGS): iStent, trabectome; for mild-moderate glaucoma (often combined with cataract surgery)
• Cyclophotocoagulation: for refractory end-stage glaucoma

Referral Criteria

• Raised IOP with suspicious disc or field defect: urgent ophthalmology referral
• Established glaucoma: lifelong ophthalmology follow-up
• Rapidly progressing: specialist glaucoma service

• POAG is a lifelong condition; treatment slows but does not reverse damage
• Treatment reduces IOP by 25-30% and significantly reduces visual field loss progression
• LiGHT trial: SLT as effective as drops for first-line IOP reduction
• Untreated: progressive bilateral visual field loss → tunnel vision → blindness
• Normal-tension glaucoma: treatment still beneficial (CNTGS trial: 30% IOP reduction slowed progression)
• CVI registration: approximately 10% of glaucoma patients become registered sight impaired
• Adherence is a major challenge (50% non-adherent at 1 year)

NICE NG81 — Treatment Pathway

Types of Glaucoma