anterior uveitis

DEFINITION/ANATOMY: The uvea consists of iris, ciliary body, and choroid. Anterior uveitis involves the iris (iritis) and/or ciliary body (iridocyclitis). It is the most common type of uveitis (~75-90%).

PATHOPHYSIOLOGY: Immune-mediated inflammation (often type IV and immune-complex mechanisms) breaks down the blood-aqueous barrier. Protein leaks into the aqueous humor (flare) and WBCs accumulate (cells). Ciliary muscle spasm causes pain and photophobia; iris sphincter spasm causes miosis.

CLINICAL FEATURES: Acute onset of eye pain, photophobia, redness, tearing, and decreased vision. Exam shows circumlimbal (ciliary) injection/flush, small or irregular pupil, and a sluggish pupillary response. Slit-lamp exam is diagnostic and shows cells and flare in the anterior chamber. Other findings include hypopyon (layered WBCs), keratic precipitates (inflammatory cells on the corneal endothelium; "mutton-fat" KPs suggest granulomatous disease), and iris nodules (Koeppe at the pupillary margin, Busacca within the iris stroma; both in granulomatous disease). Pain may worsen with accommodation or with light shone in the contralateral eye (consensual photophobia).

ETIOLOGY/ASSOCIATIONS: - HLA-B27–associated seronegative spondyloarthropathies: ankylosing spondylitis (the classic association), reactive arthritis (conjunctivitis, urethritis, arthritis), psoriatic arthritis, and IBD. Usually acute, unilateral, and often recurrent or alternating between eyes. - Juvenile idiopathic arthritis (oligoarticular, ANA+): typically chronic, insidious, and WHITE (non-painful, non-red) eye, so screening is needed. - Sarcoidosis (granulomatous; bilateral hilar lymphadenopathy, noncaseating granulomas). - Infections: HSV/VZV (with dendritic keratitis or zoster ophthalmicus), syphilis, TB, Lyme. - Others: Behçet disease (hypopyon uveitis with oral/genital ulcers), Fuchs heterochromic iridocyclitis, trauma, drug-induced (rifabutin, bisphosphonates, checkpoint inhibitors), tubulointerstitial nephritis and uveitis (TINU), multiple sclerosis (more often intermediate uveitis). Many cases are idiopathic.

DIFFERENTIAL (board pearls): Acute angle-closure glaucoma has a mid-dilated fixed pupil, a hazy cornea, and very high IOP, whereas uveitis has a small pupil and normal or low IOP. Conjunctivitis causes discharge but no photophobia or decreased vision, and the injection is diffuse rather than circumlimbal. Keratitis and corneal abrasion are seen on fluorescein staining. Scleritis causes severe boring pain and is associated with RA and GPA.

COMPLICATIONS: Posterior synechiae (iris adheres to lens, causing an irregular pupil), peripheral anterior synechiae, secondary glaucoma (including pupillary block/iris bombé), cataract (also from chronic steroids), band keratopathy (esp. JIA), cystoid macular edema, and vision loss.

WORKUP: Slit-lamp exam. First-episode, unilateral, mild cases may not need a systemic workup. Recurrent, bilateral, granulomatous, or severe cases prompt labs and imaging: HLA-B27, ESR/CRP, ACE/lysozyme and chest imaging (sarcoid), RPR/FTA-ABS (syphilis), TB testing, and ANA (JIA).

TREATMENT: Topical corticosteroids (prednisolone acetate) to reduce inflammation, plus cycloplegic/mydriatic agents (e.g., cyclopentolate, atropine) to relieve ciliary spasm/pain and prevent posterior synechiae. Treat any underlying cause (antivirals for HSV/VZV, antibiotics for syphilis/TB). For refractory or chronic disease (e.g., JIA), use steroid-sparing immunosuppressants, with TNF inhibitors (adalimumab) as a key option. Monitor IOP because of steroid-induced and inflammatory glaucoma.

HIGH-YIELD CONTRAST: Anterior uveitis involves the iris/ciliary body and is painful with a small pupil. Posterior uveitis involves the choroid/retina, causes floaters and visual loss with little pain, and is associated with toxoplasmosis, CMV retinitis, and sarcoid.