See BCSC Section 8, External Disease and Cornea, and Section 9, Uveitis and Ocular Inflammation, for in-depth discussion of episcleritis and scleritis, including pathogenesis, clinical presentation, laboratory evaluation, and management.
Episcleritis is classified as simple or nodular. Simple episcleritis is a self-limited, often idiopathic condition. Histologic examination shows vascular congestion, stromal edema, and a chronic nongranulomatous perivascular inflammatory infiltrate that is composed primarily of lymphocytes.
Nodular episcleritis more often occurs in the setting of systemic inflammatory conditions such as rheumatoid arthritis. It is characterized by tender, elevated, mobile pink-red nodules on the anterior episclera. Histologically, the nodules are often composed of a granulomatous inflammatory infiltrate surrounding a focus of necrobiosis (collagen decay), similar to rheumatoid nodules in subcutaneous tissue.
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.