Overview

Width≈1–2 mm

At the limbus the regular, transparent corneal stroma merges with the irregular, opaque scleral stroma, and the corneal epithelium becomes continuous with the conjunctival epithelium. Bowman layer ends here and Descemet membrane terminates as Schwalbe line — the anterior boundary of the drainage angle seen on gonioscopy.

The basal epithelium in the palisades of Vogt contains limbal epithelial stem cells, which continually renew the corneal epithelium and act as a barrier preventing conjunctival epithelium and vessels from growing onto the cornea. On its inner aspect the limbus forms the outer wall of the iridocorneal (drainage) angle: the scleral sulcus houses the trabecular meshwork and the canal of Schlemm, bounded posteriorly by the scleral spur.

The limbus is an important surgical landmark: incisions for cataract and glaucoma surgery are made here, and the rectus insertions are measured from it.

Location: Circular band around the periphery of the cornea where it joins the sclera; deep to it lies the iridocorneal angle.

Parts & subdivisions

Palisades of Vogt (limbal stem-cell niche)
Radial fibrovascular ridges housing the stem cells that regenerate the corneal epithelium.
Schwalbe line
Termination of Descemet membrane; anterior limit of the trabecular meshwork.
Trabecular meshwork
Spongy filter through which ≈80–90% of aqueous humour leaves the eye.
Canal of Schlemm
Circumferential endothelium-lined channel collecting aqueous from the meshwork.
Scleral spur
Ridge of sclera behind the canal; attachment of the longitudinal ciliary muscle.

Anatomy

Arterial supply: Limbal capillary arcades from the anterior ciliary arteries (from muscular branches of the ophthalmic artery).

Function

Regenerate the corneal epithelium (limbal stem cells)
Drain aqueous humour via the iridocorneal angle
Nourish the peripheral cornea via its capillary arcades

Clinical significance

Limbal stem-cell deficiency

Chemical (especially alkali) burns, Stevens–Johnson syndrome or aniridia destroy limbal stem cells; conjunctival epithelium and vessels then invade the cornea, causing opacity. Treated with limbal stem-cell transplantation.

Ciliary flush and corneal arcus

A ring of redness concentrated at the limbus (ciliary flush) indicates deep inflammation — keratitis, anterior uveitis or acute angle-closure glaucoma — rather than conjunctivitis. Arcus (a grey-white lipid ring just inside the limbus) is common with age; in a patient <≈45 years it suggests hyperlipidaemia.

Compiled from standard anatomy and physiology references — see the Special Senses sources. For education only; not medical advice.