Therapy insight: scleritis and its relationship to systemic autoimmune disease

The term scleritis describes a chronic inflammation that involves the outermost coat and skeleton of the eye. Disease can be isolated to the eye, but in up to half of affected individuals it occurs in the context of an immune-mediated systemic inflammatory condition, such as rheumatoid arthritis or Wegener's granulomatosis. Although uncommon, scleritis is often extremely painful, can lead to vision-threatening complications (and involvement of other ocular tissues), and is considered to confer an increased risk of mortality in patients with rheumatoid arthritis. Pathogenic mechanisms in scleritis are poorly understood, but enzymatic degradation of collagen fibrils by resident cells and infiltrating leukocytes seems to be a key feature. Several forms of inflammation can be distinguished histologically; interestingly, although the disease typically presents with engorgement of scleral vessels, vasculitis is not universally present at the microscopic level. Although some patients with scleritis respond well to treatment with NSAIDs, aggressive systemic therapy is often required to obtain a favorable outcome, particularly when systemic disease coexists. The mainstay of treatment is oral prednisone, but this agent is usually combined with a steroid-sparing immunosuppressive drug. New therapies presently under investigation for scleritis include local corticosteroid injections and various biologic agents.