Uveitis

Uveitis is inflammation of the uvea, the middle, vascular layer of the eye comprising the iris, ciliary body, and choroid, and of adjacent intraocular structures. Anterior uveitis, affecting the iris and ciliary body, is the most common form and a characteristic anterior segment disease; uveitis as a whole is an important cause of visual loss in working-age adults.

Definition

Uveitis is intraocular inflammation involving the uvea (iris, ciliary body, choroid), classified anatomically by the primary site of inflammation into anterior, intermediate, posterior, and panuveitis, as standardised by the SUN Working Group.

Scope

This entry covers the definition and anatomical classification of uveitis (anterior, intermediate, posterior, panuveitis) following the SUN Working Group framework, the immune mechanisms involved, common systemic associations, and the burden of uveitis-related visual loss. It is a reference overview and does not provide diagnostic or treatment guidance. As an anterior segment topic it focuses on anterior uveitis while noting the broader classification.

Key concepts

• Anatomical classification (anterior, intermediate, posterior, panuveitis)
• SUN Working Group nomenclature
• Anterior uveitis (iritis, iridocyclitis)
• HLA-B27-associated uveitis
• Infectious versus non-infectious uveitis
• Immune-mediated intraocular inflammation
• Complications: cataract, glaucoma, macular oedema

Mechanisms

Uveitis arises when intraocular immune privilege is breached and inflammatory cells enter the eye. Non-infectious uveitis is largely immune-mediated, often associated with systemic conditions and with the HLA-B27 antigen in acute anterior uveitis, while infectious uveitis results from direct invasion by organisms such as herpesviruses, Toxoplasma, or Mycobacterium tuberculosis. In anterior uveitis, inflammatory cells and protein leak into the aqueous humour (cells and flare), and may deposit on the corneal endothelium (keratic precipitates) or form adhesions between iris and lens (posterior synechiae). Persistent or recurrent inflammation drives the complications, cataract, raised intraocular pressure, and macular oedema, that account for much of the associated visual loss.

Clinical relevance

Uveitis is a significant cause of preventable visual impairment in working-age populations, and its anatomical classification and systemic associations guide how clinicians investigate intraocular inflammation. This entry describes the disease for reference and study and is not a basis for diagnosis or treatment.

Epidemiology

Anterior uveitis is the most common anatomical form, particularly in the form of acute, recurrent disease associated with HLA-B27 and spondyloarthropathies. Studies of uveitis populations show that a meaningful proportion of patients sustain visual loss, much of it from treatable complications such as cataract and macular oedema, underscoring uveitis as a cause of avoidable working-age blindness.

History

Before standardisation, uveitis terminology varied widely between centres, hampering research comparability. The Standardization of Uveitis Nomenclature (SUN) Working Group's first international workshop (reported in 2005) established consensus definitions, an anatomical classification, and grading schemes for anterior chamber cells and flare, which remain the reference framework for describing and reporting uveitis.

Debates

Anatomical versus aetiological classification

The SUN anatomical scheme classifies uveitis by the primary site of inflammation, but clinicians also need aetiological (infectious versus non-infectious, syndromic) categorisation; reconciling these complementary frameworks remains an ongoing nomenclature effort.

Seminal works

• jabs-2005-sun
• durrani-2004

Frequently asked questions

What is anterior uveitis?

Anterior uveitis is inflammation centred on the front of the uvea, the iris (iritis) and ciliary body (iridocyclitis). It is the most common form of uveitis and presents with a red, painful, light-sensitive eye and inflammatory cells in the anterior chamber.

Is uveitis always caused by an eye infection?

No. Uveitis can be infectious (for example herpesvirus, toxoplasmosis, or tuberculosis) or non-infectious and immune-mediated, often linked to systemic conditions such as HLA-B27-associated spondyloarthropathies. Distinguishing the two is central to evaluation.