Overview

The uvea (Latin uva, grape — from its dark, grape-like appearance when the sclera is peeled away) lies between the sclera and retina. It is continuous from the optic disc to the pupil and has three regions: the choroid (posterior, nourishing the outer retina), the ciliary body (producing aqueous humour and controlling accommodation) and the iris (controlling pupil size).

Its abundant melanocytes absorb stray light, reducing internal reflections that would blur the retinal image — the same principle as the black interior of a camera. Its rich vasculature (the choroid has the highest blood flow per gram of any tissue in the body) supplies nutrients and removes heat generated at the photoreceptor layer.

The uvea is supplied by the ciliary arteries (short and long posterior, anterior) from the ophthalmic artery and drained mostly by the vortex veins.

Location: Middle layer of the eyeball, between sclera (outside) and retina (inside).

Parts & subdivisions

Choroid
Posterior two-thirds; vascular and pigmented; supplies photoreceptors and RPE.
Ciliary body
Ring from ora serrata to iris root; ciliary muscle and aqueous-producing processes.
Iris
Anterior diaphragm with central pupil; sphincter and dilator pupillae.

Anatomy

Arterial supply: Short posterior ciliary arteries (choroid), long posterior ciliary and anterior ciliary arteries (ciliary body and iris, forming the major arterial circle of the iris).
Venous drainage: Vortex veins (usually 4, one per quadrant, exiting behind the equator) → superior and inferior ophthalmic veins.

Function

Nourish the outer retina (choroid)
Absorb scattered light (melanin)
Produce aqueous humour (ciliary epithelium)
Accommodation (ciliary muscle) and control of pupil size (iris)

Clinical significance

Uveitis

Inflammation of the uvea. Anterior uveitis (iritis): painful red eye with ciliary flush, photophobia, small irregular pupil, cells and flare in the anterior chamber and keratic precipitates; associated with HLA-B27 spondyloarthropathies (ankylosing spondylitis, reactive arthritis, IBD), sarcoidosis and juvenile idiopathic arthritis. Posterior uveitis (choroiditis) causes floaters and visual loss (toxoplasmosis, CMV, sarcoid, TB). Treated with topical steroids and cycloplegics.

Uveal melanoma

The most common primary intraocular malignancy in adults, usually arising in the choroid; spreads haematogenously (no lymphatics) with a predilection for the liver.

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