Sympathetic ophthalmia was given its complete clinical description by William Mackenzic in 1840, and fully described in terms of its histopathology by Ernst Fuchs in 1905. A review of epidemiologic data from the 19th and 20th centuries reveals that acceptable statistical studies have yet to be carried out, but suggests that the disease has always been of extremely low incidence. Further, there does not appear to be a markedly decreased incidence in the "modern era." The etiology of the disease remains elusive, although the pathogenesis appears to be due to delayed hypersensitivity (cell-mediated immunity), possibly directed at a surface membrane antigen that is shared by photoreceptors, retinal pigment epithelium and choroidal melanocytes. The only effective therapy remains preventive enucleation of the injured eye, despite modern usage of immunosuppressive agents. Studies have suggested that early enucleation of a blind exciting eye can improve the prognosis for the sympathizing eye.