Histopathological evaluation of scleritis

The sclera is an uncommon site of primary inflammation. Biopsy is infrequently employed in the evaluation of scleritis, but familiarity with its differential diagnosis is instrumental in ensuring efficient histological evaluation. This review provides a clinical overview of scleritis and describes the context in which scleral biopsy might arise. Most cases are associated with systemic autoimmune disease, but a sizeable proportion occur as an isolated disorder. Conditions mimicking autoimmune scleritis include infection and neoplasm. Histological patterns of inflammation in eyes removed surgically or at autopsy have been placed into three groups: (1) autoimmune scleritis characterised by varying mixtures of palisading granulomas, necrosis and vasculitis; (2) infectious scleritis, characterised by acute inflammation and necrosis; and (3) idiopathic scleritis, characterised by chronic non-specific inflammation with follicles and varying amounts of fibrosis. This traditional system of classification may be oversimplified. Aetiological or categorical classification is not always possible on small biopsies given the histopathological overlap of infectious and non-infectious scleritis.