Uveitis and Ocular Immunology
Core concepts
Understand the classification of uveitis by location (anterior, intermediate, posterior, panuveitis) and by cause (infectious vs noninfectious). Know the classic associations: HLA-B27 with anterior uveitis, sarcoidosis with granulomatous uveitis, toxoplasmosis with focal retinochoroiditis, and Behçet disease with hypopyon. Learn the signs of anterior uveitis: cells and flare, keratic precipitates, posterior synechiae. Understand the role of topical steroids and cycloplegics in anterior uveitis and when to use systemic immunosuppression.
Traps
Do not start steroids before ruling out infectious causes in severe or atypical uveitis. A hypopyon can be infectious endophthalmitis or Behçet; context matters. Know that intermediate uveitis (pars planitis) shows snowbanking and vitreous cells. In toxoplasmosis, classic "headlight in the fog" appearance. Remember that uveitis can be the first sign of a systemic disease.
Rule of thumb
Anterior uveitis with a hypopyon and no infection history suggests Behçet or HLA-B27; unilateral focal retinochoroiditis suggests toxoplasmosis. Always consider masquerade syndromes in atypical or refractory uveitis.
Worked example
A young adult with recurrent painful red eye, photophobia, and cells/flare in the anterior chamber, with a history of ankylosing spondylitis. This is HLA-B27-associated anterior uveitis; treat with topical steroid and cycloplegic, and coordinate with rheumatology.