Uveitic Retinal Disease & Posterior Uveitis Syndromes

SUN Anatomic Classification

The Standardization of Uveitis Nomenclature (SUN) Working Group classifies uveitis by its primary anatomic site of inflammation rather than by cause, so the terminology stays consistent across etiologies. Anterior uveitis centers on the anterior chamber. Intermediate uveitis is defined by primary inflammation in the vitreous cavity, a category that includes pars planitis and posterior cyclitis. Posterior uveitis primarily involves the retina, the choroid, or both. Panuveitis involves all three compartments at once, with no single site predominating.

SUN Duration & Grading

SUN also standardizes chronicity language. Uveitis that resolves within three months of stopping treatment is "limited"; inflammation persisting beyond three months is "persistent," or chronic. The distinction shapes treatment planning and the prognosis discussion with the patient.

For severity, SUN grades anterior chamber cell, the white blood cells suspended in the anterior chamber and the hallmark sign of active anterior inflammation, on a standardized scale from 0 to 4+ (4+ meaning too numerous to count). This gives clinicians and researchers a common yardstick for comparing severity across visits and across studies.

Keratic Precipitates

Keratic precipitates (KPs), inflammatory cell deposits on the corneal endothelium, are one of the most useful bedside clues to the underlying inflammatory mechanism.

HLA-B27 Anterior Uveitis

Ankylosing spondylitis and the other spondyloarthropathies are the classic systemic associations of HLA-B27-positive uveitis. It typically presents as acute, recurrent anterior uveitis, often alternating sides, and is nongranulomatous. Rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis are HLA-B27-negative and fall outside this association.

Behçet Disease

Behçet disease produces a distinctive occlusive retinal vasculitis and panuveitis. Its hallmark hypopyon is mobile and shifting, and unlike most hypopyons it causes little pain; the diagnosis is supported by the mucocutaneous findings of recurrent oral and genital ulcers. Because the vasculitis is recurrent and occlusive, repeated ischemic episodes cause capillary nonperfusion and carry a real risk of secondary retinal neovascularization, a more destructive course than the predominantly nonocclusive inflammation typical of the other entities covered here.

Sarcoidosis

Sarcoid-associated uveitis is granulomatous. The key supportive systemic finding is bilateral hilar lymphadenopathy on chest imaging, often paired with an elevated serum ACE level. On the retina, sarcoid produces periphlebitis with perivascular granulomatous exudate, seen clinically as waxy yellow-white "candle wax drippings" (taches de bougie), one of the most recognizable retinal findings in this differential.

Vogt-Koyanagi-Harada Disease

VKH is a granulomatous panuveitis that progresses through defined clinical stages. Its convalescent stage, following the initial acute uveitic stage, brings the "sunset glow fundus": diffuse, orange-red choroidal depigmentation as progressive melanocyte destruction leaves the RPE and choroid thin enough to reveal the sclera and choroidal vessels beneath.

Ocular Toxoplasmosis

Toxoplasma gondii is the most common infectious cause of posterior uveitis worldwide. Recurrent disease reactivates at the border of an old, pigmented chorioretinal scar left by congenital or earlier infection, producing a fluffy yellow-white focus of active retinochoroiditis with overlying vitritis. The hazy vitreous over the active lesion gives it the classic "headlight in the fog" appearance: glowing and indistinct.

Fuchs, Birdshot & Frosted Branch Angiitis

Fuchs Heterochromic Iridocyclitis

Fuchs is characterized by small, stellate keratic precipitates scattered diffusely across the entire corneal endothelium, rather than clustering inferiorly in Arlt's triangle as in most other anterior uveitides. This diffuse stellate pattern is a useful bedside clue even before heterochromia is appreciated.

Birdshot Chorioretinopathy

Birdshot chorioretinopathy is strongly associated with HLA-A29: over 90% of patients carry this allele, one of the strongest HLA-disease associations in all of ophthalmology. In the right clinical setting, multiple cream-colored, ovoid choroidal lesions radiating from the disc make the diagnosis straightforward.

Frosted Branch Angiitis

Frosted branch angiitis is a rare, severe form of retinal vasculitis, producing dense, translucent perivascular sheathing along both arterioles and venules that resembles frost-covered tree branches. It can be idiopathic, or secondary to infections such as CMV retinitis, or to severe systemic inflammatory disease.

CMV retinitis itself develops almost exclusively once the CD4 count falls below 50 cells/mm³, spreading from the peripheral retina toward the posterior pole and producing the classic "pizza pie" fundus of granular whitening with scattered hemorrhage. Vitreous inflammation stays mild, a clue that separates it from other HIV-related retinal disease. Durable control needs both direct antiviral treatment and restored immune function through antiretroviral therapy.

Uveitic Cystoid Macular Edema

Chronic intraocular inflammation disrupts the blood-retinal barrier and lets fluid accumulate in the perifoveal capillaries. The resulting uveitic cystoid macular edema is the most common cause of vision loss in chronic uveitis, even when anterior segment inflammation is otherwise well controlled. When topical corticosteroids fall short, periocular (sub-Tenon's) or intravitreal corticosteroid injection delivers a much higher local dose to the posterior segment, controlling vascular leakage and edema more effectively than topical therapy alone.

High-Yield Pearls

• Mutton-fat KPs = granulomatous (sarcoid, VKH); fine white KPs = nongranulomatous (HLA-B27); diffuse stellate KPs = Fuchs.
• Painless, mobile hypopyon + oral/genital ulcers = Behçet.
• Bilateral hilar adenopathy + candle-wax-drippings retinal vasculitis = sarcoidosis.
• Sunset glow fundus develops in VKH's convalescent stage, after the acute uveitic stage.
• Headlight-in-the-fog lesion at the edge of an old scar = reactivated ocular toxoplasmosis.
• HLA-A29 is one of medicine's strongest HLA associations: think birdshot.
• Uveitic CME, not the anterior inflammation itself, is the leading cause of vision loss in chronic uveitis.

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