Glaucoma

Overview

Glaucoma refers to a group of optic neuropathies characterized by increased intraocular pressure (IOP), leading to progressive retinal and optic nerve damage. It is a leading cause of irreversible blindness worldwide and is especially dangerous due to its asymptomatic onset in many cases. This article outlines the key mechanisms, classifications, clinical signs, and management strategies for glaucoma.

Definition

A progressive optic neuropathy caused by increased intraocular pressure (IOP), typically resulting from impaired drainage of aqueous humour, which damages the optic nerve and retina.

Aetiology

• Imbalance between production and drainage of aqueous humour
• Impaired drainage via the Canal of Schlemm
• Can be congenital, primary, or secondary (e.g. due to trauma or inflammation)

Pathogenesis

• Overproduction or poor drainage of aqueous humour
  → ↑ Intraocular Pressure (IOP)
  → Compression of optic nerve fibres and microvasculature
  → Optic nerve head cupping + retinal ischaemia
  → Gradual peripheral → central vision loss

Classification

Open-Angle Glaucoma

• The iridocorneal angle is anatomically open
• Drainage is impaired due to trabecular meshwork dysfunction
• Progression: Chronic, insidious
• Symptoms: Often asymptomatic until advanced vision loss
• Epidemiology: Most common form globally

Closed-Angle Glaucoma (Angle-Closure Glaucoma)

• The iridocorneal angle is anatomically narrow
• Iris blocks the trabecular meshwork → sudden rise in IOP
• Acute presentation: Painful red eye, blurred vision, nausea
• Ophthalmological emergency — requires urgent intervention

Congenital or Juvenile Glaucoma

• Due to developmental abnormalities of the anterior chamber angle
• May be inherited or associated with intrauterine infections
• Presents in infancy or early childhood with large eyes, photophobia, tearing

Clinical Features

Acute Angle-Closure Glaucoma

• Sudden, severe eye pain
• Headache
• Nausea and vomiting
• Decreased vision or visual halos
• Red eye with mid-dilated, non-reactive pupil
• Unilateral presentation common

Chronic Glaucoma (Open-Angle)

• Asymptomatic until late stages
• Gradual peripheral vision loss (“tunnel vision”)
• Optic disc cupping seen on fundoscopy
• Elevated IOP on tonometry

Investigations

• Tonometry – Measures IOP
• Gonioscopy – Visualizes the angle between iris and cornea
• Visual Field Testing – Detects peripheral field loss
• Optic Disc Examination – Cup-to-disc ratio evaluation
• OCT (Optical Coherence Tomography) – Retinal nerve fibre analysis

Management

Medical

• Topical Agents:
  • Beta-blockers (e.g. timolol) – ↓ aqueous humour production
  • Prostaglandin analogues (e.g. latanoprost) – ↑ uveoscleral outflow
  • Alpha-agonists (e.g. brimonidine)
  • Carbonic anhydrase inhibitors (e.g. dorzolamide)
• Pupillary constrictors (e.g. pilocarpine) for angle-closure
• Avoid mydriatics (dilating agents), which worsen angle-closure

Surgical

• Laser trabeculoplasty (open-angle glaucoma)
• Laser iridotomy (closed-angle glaucoma)
• Trabeculectomy for refractory cases
• Goniotomy or trabeculotomy in congenital cases

Complications

• Progressive vision loss → legal blindness if untreated
• Permanent optic nerve damage
• Acute angle-closure can lead to rapid loss of vision without prompt treatment

Summary

Glaucoma is a spectrum of conditions involving increased intraocular pressure and optic nerve damage, commonly resulting from impaired aqueous humour drainage. The two main types — open-angle and closed-angle glaucoma — differ in onset and presentation but both can cause irreversible vision loss. Early diagnosis through routine screening, especially in at-risk populations, is essential. For related topics, visit our Nervous System Overview page.