Endocrine ophthalmopathy is regarded as organ specific disease of autoimmunological origin. It occurs most frequently in patients with Graves disease, less frequently in those with Hashimoto thyroiditis. The presence of HLA DR-3 and HLA b-8 antigens, cigarette smoking, treatment with radioiodine, and thyroid function disturbances predispose for the development of the disease. On the other hand, the most important pathogenetic mechanism is fibroblast stimulation and increased collagen and glucosaminoglycans production within the extrabulbar muscle interstitium.