Glaucoma and the optic nerve
- Lesion
Glaucoma is damage to the optic nerve, usually with high eye pressure, that slowly narrows the visual field; it is a leading cause of irreversible blindness.
What it is
Glaucoma is a group of diseases with a common end: loss of retinal ganglion cells and their axons, seen as cupping of the optic disc and field loss. Most cases have raised intraocular pressure from impaired outflow of aqueous humour, but some occur at normal pressure. Classification depends on the drainage angle: open, closed, or blocked from birth, and on whether the cause is primary or secondary (inflammation, blood, pigment, new vessels, lens material, exfoliation material).
Step by step
- The ciliary body secretes aqueous humour into the posterior chamber.
- Aqueous flows through the pupil to the angle and drains through the trabecular meshwork and Schlemm canal.
- Outflow is blocked or reduced, and intraocular pressure rises.
- Pressure strains the lamina cribrosa, where ganglion cell axons leave the eye.
- Axonal transport fails and ganglion cells die by apoptosis.
- The cup enlarges and the visual field narrows from the periphery.
Types of glaucoma
| Type | Mechanism | Clue |
|---|---|---|
| Primary open-angle | Reduced trabecular outflow | Painless, gradual peripheral field loss, cupping |
| Primary angle-closure | Iris apposed to trabecular meshwork | Acute painful red eye, halos, high pressure |
| Primary congenital | Abnormal angle development | Buphthalmos, tearing, light sensitivity |
| Neovascular | Fibrovascular membrane closes the angle | Diabetic retinopathy, retinal vein occlusion |
| Pseudoexfoliation | Fibrillar material clogs the meshwork | Older adults, flakes on lens capsule |
| Pigmentary | Iris pigment rubs off and clogs the meshwork | Young myopic men |
| Steroid-induced | Reduced outflow from corticosteroids | Topical or systemic steroid use |
Clinical notes
- Screening with tonometry and disc examination is key because early open-angle glaucoma is silent; a Colombian survey links it to a real share of visual impairment.
- Acute angle closure is an emergency; pressure must be lowered within hours to save the nerve.
Test yourself
Think of the answer, then tap the question to see it.
What tissue is the main site of resistance in primary open-angle glaucoma?
The trabecular meshwork and Schlemm canal, where outflow is reduced despite an open angle.
Which systemic disease commonly leads to neovascular glaucoma?
Diabetes mellitus, through proliferative diabetic retinopathy; central retinal vein occlusion is another cause.
What does glaucoma do to the optic disc?
Ganglion cell axons are lost, so the cup enlarges and deepens and the neuroretinal rim thins.
Elsewhere in DurgiPedia
- Aqueous humor and intraocular pressure
- The anterior chamber and the drainage angle
- The optic disc: cup, rim and colour
- Tonometry: measuring intraocular pressure
- Acute angle closure: what to do before the ophthalmologist
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Glaucoma | Blindness | MedlinePlus (MedlinePlus, US National Library of Medicine, 2026); Self-reported glaucoma prevalence and related factors, contribution to reported visual impairment, and functional burden in a cross-sectional study in Colombia (Europe PMC, 2026).
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Representative model, for educational purposes only.