Thyroid-associated orbitopathy (TAO) is a common manifestation of Graves’ disease. Th e aim of the study was to assess the six percent of patients with TAO that develop dysthyroid optic neuropathy (DON), which is the most serious complication of TAO. As DON can cause permanent damage, it is essential to detect DON early when visual loss is still reversible. Color Doppler ultrasound is a noninvasive diagnostic method, which may be useful in early detection of DON. Th irty-six patients with confi rmed Graves’ disease and active TAO were included, 21 (58%) of them with early DON (eDON) and 15 (42%) free from any signs of eDON. All study patients underwent Doppler ultrasound examination to determine the blood fl ow rates in the internal carotid artery, ophthalmic artery, and central retinal artery. Study results showed color Doppler ultrasound examination to have a potential to detect orbital blood fl ow changes in patients with eDON. Early detection of DON may result in earlier treatment and prevention of permanent optic nerve damage.