Uveitis Anterior

01Pathophysiology

Anterior uveitis refers to inflammation of the uveal tract limited to the anterior segment, involving the iris (iritis), the ciliary body (iridocyclitis), or both. The uveal tract is a highly vascular structure, making it particularly susceptible to immune-mediated inflammatory processes.

The underlying mechanism in most non-infectious cases involves a T-cell-mediated autoimmune response directed against uveal antigens. In genetically predisposed individuals, particularly those carrying HLA-B27, molecular mimicry between microbial antigens and self-antigens is thought to trigger this inflammatory cascade. Activated T-cells and macrophages infiltrate the iris and ciliary body, releasing cytokines that increase vascular permeability. This causes protein leakage (flare) and white blood cell migration (cells) into the anterior chamber, which are the hallmark findings on slit-lamp examination.

The inflammation of the ciliary body leads to spasm of the ciliary muscle, which is responsible for the deep, aching eye pain. Ciliary spasm also causes the pupil to constrict (miosis), distinguishing this from acute angle-closure glaucoma, which presents with a mid-dilated, fixed pupil. The concept of consensual photophobia is a high-yield discriminator: when light is directed into the unaffected eye, the consensual pupillary constriction in the inflamed eye triggers ciliary spasm and pain. This finding is nearly pathognomonic for anterior uveitis and is frequently tested.

The ciliary flush (also called perilimbal injection) results from dilation of the deep episcleral and ciliary vessels that encircle the limbus. This pattern of redness is distinct from the diffuse conjunctival injection seen in conjunctivitis, where the redness is most prominent in the fornices and fades toward the limbus.

In severe or prolonged inflammation, inflammatory cells can layer dependently in the anterior chamber, forming a hypopyon, a visible white fluid level. This is classically associated with Behcet disease and HLA-B27-associated uveitis, though it can occur in endophthalmitis as well.

Chronic or recurrent anterior uveitis can lead to posterior synechiae, which are adhesions between the iris and the anterior lens capsule. These adhesions can cause an irregular, poorly dilating pupil and, if circumferential (seclusio pupillae), can block aqueous humor outflow and precipitate secondary angle-closure glaucoma.

02Classification and Clinical Manifestation

Duration and Course:

Systemic Associations

03Diagnostic Workup

The slit-lamp examination is the cornerstone of diagnosis. It allows direct visualization of inflammatory cells floating in the aqueous humor and the protein-rich haze called flare. The grading of cells (0 to 4+) determines disease severity and guides treatment intensity.

Keratic precipitates (KPs) are clumps of inflammatory cells deposited on the corneal endothelium. Their morphology provides a diagnostic clue. Fine, small KPs suggest a non-granulomatous process (typical of HLA-B27-associated disease), while large, greasy "mutton-fat" KPs suggest a granulomatous etiology such as sarcoidosis, tuberculosis, or syphilis.

For a first episode of mild, unilateral acute anterior uveitis in a young patient, extensive laboratory workup is generally not required. However, when the uveitis is recurrent, bilateral, chronic, granulomatous, or associated with posterior segment involvement, a directed systemic workup becomes necessary. The minimum panel typically includes HLA-B27, chest X-ray, syphilis serologies, and tuberculosis screening.

The examiner may present a vignette where the patient has recurrent anterior uveitis and then ask what additional evaluation is needed. In that scenario, the answer is to look for an underlying systemic condition, and HLA-B27 testing combined with a thorough review of systems for spondyloarthropathy is the best next step.

04Management and Treatment

Topical prednisolone acetate 1% is the drug of choice. It is preferred over prednisolone sodium phosphate because the acetate formulation penetrates the cornea more effectively. Aggressive initial dosing (every 1-2 hours) followed by a gradual taper is critical. A common exam pitfall involves abruptly stopping corticosteroids, which leads to rebound inflammation.

Cycloplegic agents serve two purposes. First, they paralyze the ciliary muscle, providing pain relief by eliminating the spasm responsible for the aching discomfort and photophobia. Second, they dilate the pupil and keep the iris mobile, preventing the formation of posterior synechiae. Atropine 1% (longest-acting) is reserved for severe cases; cyclopentolate or homatropine is preferred for moderate cases because their shorter duration allows more frequent reassessment of pupillary function.

For patients with chronic or recurrent disease requiring prolonged corticosteroid use, steroid-sparing immunosuppressive agents are introduced. Methotrexate is the most commonly used first-line steroid-sparing agent. This is particularly important in JIA-associated uveitis, where chronic low-grade inflammation can silently damage the eye.

When an infectious cause is identified, treating the infection takes priority. Initiating corticosteroids without antimicrobial coverage in herpetic or syphilitic uveitis can worsen the infection.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on anterior uveitis questions is by confusing the pattern of eye redness. The vignette will describe perilimbal (ciliary) injection and test whether you can distinguish this from the diffuse conjunctival injection of conjunctivitis or the sectoral redness of episcleritis. If the redness is concentrated around the corneal limbus, think uveitis or keratitis, not conjunctivitis.

The second major trap involves consensual photophobia. If the vignette states that shining a light into the unaffected eye causes pain in the affected eye, this essentially confirms anterior uveitis. This finding is tested because it demonstrates an understanding of the consensual pupillary reflex triggering ciliary spasm in the inflamed eye.

Do not forget the JIA-uveitis connection. A young girl with oligoarticular JIA and a positive ANA requires routine ophthalmologic screening even in the absence of eye symptoms, because her uveitis is characteristically chronic and asymptomatic until complications (band keratopathy, cataracts, glaucoma) have already developed. The exam tests whether you know to screen proactively.

Another frequently tested concept is the association between HLA-B27 and recurrent acute anterior uveitis. When a patient with known ankylosing spondylitis or reactive arthritis presents with a red, painful eye and photophobia, anterior uveitis should be the leading diagnosis. The test-writer is evaluating your ability to link systemic autoimmune disease to ocular manifestations.

Finally, always remember that syphilis can mimic any form of uveitis. In any atypical or treatment-refractory case, syphilis serologies should be checked. Missing syphilis as a cause of uveitis is a classic diagnostic error that exam writers exploit.