Data on the incidence of GO are limited (11). In a population-based setting in USA, an adjusted rate of 16 cases per per year in women and cases per in men was reported (12). In a recent study of a large cohort of newly diagnosed Graves’ patients, about 75% had no ocular involvement at diagnosis, only 6% had moderate-to-severe GO, and % showed sight-threatening GO due to dysthyroid optic neuropathy (DON) (13) (Figure 1). In a Danish population, moderate-to-severe GO showed an incidence of /million per year (women: ; men: ) (14). Ocular involvement is in most cases bilateral, although often asymmetrical, but it may be unilateral in up to 15% of cases (9). The onset of GO apparently has a bimodal peak in the fifth and seventh decades of life, but eye disease may occur at any age (15). It is more frequent in women, but men tend to have a more severe disease (15-17), as suggested by a decrease in the female/male ratio from in mild GO, to in moderately severe GO, and in severe GO (18). There is a close temporal relationship between the onset of GO and the onset of hyperthyroidism. In approximately 85% of cases GO and hyperthyroidism occur within 18 months of each other (15), although GO may both precede (about 20% of cases) or follow (about 40% of cases) the onset of hyperthyroidism (15).