Episcleritis is a relatively common, benign cause of red eye, due to inflammation of the episcleral tissues. Nodular episcleritis is characterized by a clearly defined elevated area of inflammation. In simple episcleritis, vascularization is present without an obvious nodule.
Differentials include: scleritis (inflammation goes deeper in the tissues and is much more serious), allergic conjunctivitis, and uveitis.
Los Alamos Family Eyecare, P.C. 