Scleritis is a severe, painful inflammatory condition of the sclera, most commonly associated with systemic autoimmune disease (rheumatoid arthritis, GPA, SLE). Anterior diffuse scleritis causes generalised scleral oedema and intense photophobia; nodular/necrotizing scleritis may progress to scleral thinning (scleromalacia) with risk of perforation; posterior scleritis causes proptosis, reduced VA and choroidal folds. All types produce significant veiling luminance from photophobia, contrast reduction, and chromatic desaturation from intraocular inflammation. Severity maps to Watson clinical grading.