The anterior chamber and the drainage angle
- Anatomy and physiology
Aqueous is made behind the iris, flows through the pupil and drains at the angle between iris and cornea. If the angle narrows or clogs, pressure rises.
See it in 3D: Iris · Cornea · Ciliary body
What it is
The anterior chamber is the space between the cornea and the iris, filled with aqueous humour. At its periphery, where the iris meets the cornea, is the drainage angle with the trabecular meshwork and Schlemm canal. The balance between aqueous production by the ciliary body and outflow through the angle sets the intraocular pressure. Glaucoma drugs and surgery all act on this circuit.
Clinical anatomy
- The ciliary epithelium secretes aqueous into the posterior chamber, behind the iris.
- Aqueous flows through the pupil into the anterior chamber.
- Most leaves through the trabecular meshwork into Schlemm canal and the episcleral veins (conventional route).
- A smaller part passes through the ciliary muscle into the suprachoroidal space (uveoscleral route).
- On gonioscopy the angle shows, from front to back, Schwalbe line, trabecular meshwork, scleral spur and ciliary body band.
Physiology
- Aqueous nourishes the lens and the inner cornea, which have no blood vessels.
- Steady production and drainage keep the pressure and the shape of the eye.
- Prostaglandin analogues increase uveoscleral outflow; beta-blockers, carbonic anhydrase inhibitors and alpha agonists reduce production; pilocarpine opens the trabecular route.
Clinical correlation
- In open-angle glaucoma the angle looks normal but drains poorly; in angle closure the iris blocks it.
- Narrow angles are more common with long-sightedness, older age (the lens thickens), female sex and East Asian ancestry.
- Anticholinergic and adrenergic drugs that dilate the pupil can close a narrow angle.
- Blood (hyphema) or inflammatory cells can clog the meshwork and raise the pressure.
Next step / Initial management
- Narrow angle found on the penlight or Van Herick test: ophthalmology for gonioscopy and, if confirmed, laser iridotomy.
- Patients with narrow angles: caution with dilating drops and anticholinergic drugs, and teach the symptoms of angle closure.
- Raised pressure with an open angle: ophthalmology for glaucoma assessment.
- Hyphema after trauma: same-day ophthalmology, pressure checks, rest with the head raised.
Test yourself
Think of the answer, then tap the question to see it.
What is the main outflow route of aqueous humour?
The trabecular meshwork into Schlemm canal and the episcleral veins.
How do prostaglandin analogues lower eye pressure?
By increasing uveoscleral outflow.
Which patients have narrow angles more often?
Long-sighted, older people, women and people of East Asian ancestry.
Elsewhere in DurgiPedia
Connections
See it in 3D3
The structures of Durgical's 3D anatomy where it is found.
Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once.
Sources: Physiology, Aqueous Humor Circulation (StatPearls Publishing (NCBI Bookshelf), 2023); Intraocular Pressure (StatPearls Publishing (NCBI Bookshelf), 2024); Acute Angle-Closure Glaucoma (StatPearls Publishing (NCBI Bookshelf), 2026).
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Representative model, for educational purposes only.