Uvea

The uvea, also called the uveal tract, is the middle, pigmented, highly vascular layer of the eye. It lies beneath the sclera and above the retina, and it consists of three contiguous structures: the iris, the ciliary body, and the choroid. The uvea supplies most of the blood to the eye and plays a role in absorbing excess light.

Iris controls the size of the pupil and regulates the amount of light reaching the retina. The ciliary body includes the ciliary muscle and ciliary processes; it produces aqueous humor and adjusts lens focus (accommodation). The choroid lies between the retina and sclera and nourishes the outer retina with blood; its rich pigment helps reduce intraocular light scatter.

As a vascular, pigmented tissue, the uvea contributes to the eye's immune privilege and participates in inflammatory responses. The uveal blood supply supports retinal metabolism and ocular tissue health.

Common conditions affecting the uvea include uveitis, an inflammation that can involve any part of the uveal tract: anterior uveitis (iritis), intermediate uveitis (pars planitis), posterior uveitis (choroiditis or retinochoroiditis), and panuveitis when all regions are involved. Other disorders include uveal melanoma, the most common primary intraocular malignant tumor in adults, and benign lesions such as a choroidal nevus. Uveitis can be caused by autoimmune disease, infection, or exposure to toxins and may threaten vision if not treated.

Diagnosis relies on ophthalmic examination, slit-lamp microscopy, optical coherence tomography, and fluorescein angiography. Treatment targets the underlying cause and may include topical, periocular, or systemic corticosteroids, cycloplegic agents to relieve pain and prevent adhesions, and immunosuppressive drugs for noninfectious cases. Infectious uveitis requires specific antimicrobial therapy. Early, appropriate management reduces the risk of complications such as cataract, glaucoma, or retinal damage, and prognosis varies with etiology and response to therapy.