Uveitis: Inflammation Inside the Eye

Uveitis accounts for roughly 10–15% of total blindness in the United States and up to 25% of blindness in the developing world, according to the National Eye Institute (NEI). Despite those numbers, the condition remains poorly understood outside of ophthalmology circles — partly because "inflammation inside the eye" sounds vague, and partly because uveitis is not one disease but a family of inflammatory conditions, each with its own personality and preferred target.

What Uveitis Actually Means

The uvea is the middle layer of the eye wall, sandwiched between the outer sclera and the inner retina. It consists of three structures: the iris (the colored part), the ciliary body (which produces aqueous humor and adjusts the lens), and the choroid (a vascular layer that feeds the retina). Inflammation in any part of this layer — or, importantly, inflammation that spills into adjacent structures like the retina or vitreous humor — falls under the uveitis umbrella.

The Standardization of Uveitis Nomenclature (SUN) Working Group, an international classification effort published in the American Journal of Ophthalmology, divides uveitis into four anatomical categories:

• Anterior uveitis — inflammation primarily in the front chamber, including iritis and iridocyclitis. This is the most common form, representing approximately 50–60% of cases seen in tertiary referral centers.
• Intermediate uveitis — centered in the vitreous cavity, sometimes called pars planitis.
• Posterior uveitis — affecting the choroid and/or retina.
• Panuveitis — inflammation involving all segments.

The distinction matters because location strongly predicts both cause and prognosis.

Causes: Autoimmune, Infectious, and Mysterious

Anterior uveitis frequently associates with HLA-B27, a genetic marker also linked to ankylosing spondylitis and other spondyloarthropathies. Testing for HLA-B27 is a standard part of the workup when anterior uveitis recurs without obvious explanation.

Infectious causes span a wide range. Toxoplasmosis remains the leading cause of posterior uveitis worldwide. Tuberculosis, syphilis, herpes simplex, varicella-zoster, and cytomegalovirus all have characteristic uveitis presentations. In immunocompromised patients — particularly those with CD4 counts below 50 cells/μL — CMV retinitis was a defining complication of the AIDS epidemic before effective antiretroviral therapy changed the landscape.

Sarcoidosis deserves a special mention. It can cause uveitis in any anatomical category and often presents with granulomatous "mutton-fat" keratic precipitates that are unmistakable on slit-lamp exam. The American Academy of Ophthalmology notes that ocular involvement occurs in 25–50% of sarcoidosis patients (AAO).

And then there is the idiopathic category — meaning no cause is found despite thorough investigation. This accounts for roughly 30–40% of uveitis cases in published series, a humbling reminder that the immune system keeps its own counsel.

Symptoms and Diagnosis

The classic triad of anterior uveitis — pain, redness, and photophobia — is distinctive enough to prompt most patients to seek care relatively quickly. Posterior uveitis, by contrast, tends to announce itself with floaters and blurred vision rather than pain, which can delay diagnosis.

Slit-lamp biomicroscopy is the primary diagnostic tool. An ophthalmologist can directly observe inflammatory cells and protein flare in the anterior chamber, grading severity on a standardized scale (the SUN grading system uses a 0 to 4+ scale based on cells per high-power field). Posterior segment evaluation requires dilated fundoscopy, optical coherence tomography (OCT), and sometimes fluorescein angiography to map vascular leakage.

Laboratory workup depends on clinical context. A first episode of mild unilateral anterior uveitis in a young adult may warrant watchful waiting. Bilateral disease, recurrent episodes, granulomatous features, or posterior involvement typically trigger testing that may include chest X-ray, HLA-B27, syphilis serology (FTA-ABS), angiotensin-converting enzyme (ACE) levels, and tuberculosis screening.

Treatment Approaches

Topical corticosteroid drops — prednisolone acetate 1% is the workhorse — remain first-line therapy for anterior uveitis. Cycloplegic agents like cyclopentolate or atropine are added to reduce pain from ciliary spasm and prevent posterior synechiae (adhesions between the iris and lens that can permanently distort the pupil).

Posterior and intermediate uveitis often require more aggressive intervention. Periocular or intravitreal corticosteroid injections deliver high local concentrations. The FDA-approved intravitreal fluocinolone acetonide implant (Retisert) provides sustained release over approximately 30 months, though it carries a significant risk of cataract formation and elevated intraocular pressure (NEI).

For chronic or recurrent disease requiring long-term immunosuppression, corticosteroid-sparing agents are essential — the cumulative side effects of systemic steroids (osteoporosis, diabetes, adrenal suppression) make indefinite use untenable. Methotrexate, mycophenolate mofetil, azathioprine, and cyclosporine are all used. The Multicenter Uveitis Steroid Treatment (MUST) Trial, a landmark NIH-funded study, compared the fluocinolone implant to systemic therapy and found comparable visual outcomes at seven years, with each approach carrying a different side-effect profile (ClinicalTrials.gov).

Biologic agents have expanded the toolkit. Adalimumab (Humira) received FDA approval for non-infectious intermediate, posterior, and panuveitis in 2016, based on the VISUAL I and VISUAL II trials demonstrating reduced risk of uveitic flare.

Complications Worth Knowing

Untreated or poorly controlled uveitis can cause cataract, glaucoma, band keratopathy, cystoid macular edema, retinal detachment, and optic nerve damage. Cystoid macular edema is the single most common cause of visual loss in uveitis patients and can persist even after active inflammation resolves.

What does "chronic" uveitis mean for long-term monitoring?

The SUN Working Group defines chronic uveitis as persistent inflammation that relapses within three months of discontinuing treatment. Patients with chronic disease — particularly those with conditions like juvenile idiopathic arthritis-associated uveitis or Behçet disease — require ongoing monitoring, sometimes for decades. The American Uveitis Society recommends individualized follow-up intervals, but quarterly examinations are a common baseline for stable chronic cases.

Can uveitis be prevented?

Primary prevention is not feasible for most forms, since the triggering immune events are poorly understood. Secondary prevention — reducing flare frequency and severity — is the realistic goal and the central purpose of steroid-sparing immunosuppressive therapy.

References

• National Eye Institute — Uveitis
• American Academy of Ophthalmology — Uveitis Diagnosis
• MUST Trial — ClinicalTrials.gov
• Standardization of Uveitis Nomenclature (SUN) Working Group — American Journal of Ophthalmology

The law belongs to the people. Georgia v. Public.Resource.Org, 590 U.S. (2020)