Objective To observe the characteristics of indocyanine green angiography and fundus fluorescein angiography (ICGA amp; FFA) in anterior ischemic optic neuropathy ( AION ) , and to investigate the etiology of AION and the value of ICGA and FFA in the diagnosis and study of AION. Methods Simultaneous ICGA and FFA were performed on 32 eyes of 31 AION patients and 38 eyes of 38 non-AION patients. Results The eyes that all or a part of the optic disclies in the watershed zon es of the choroidal blood supply were significantly more in the AION group tha n those in the non-AION group (Plt; 0.005 ) . All the watershed zones through the optic disc were vertical in shape. The fluorescence filling of the inferior and superior choroidal blood vessels near the optic disc were all slower than that of the temporal and nasal choroidal blood vessels. The types of watershed zones in the AION group were highly correspondent to the ischemic areas of the optic disc . In early ICGA , no fluorescence appeared at the optic disc, and in later stage, the ischemic area revealed no fluorescence, and the other area showed mostly asymmetric fluorescence. Conclusion The onset of AION is correlative to the choroidal blood supply around the optic disc. ICGA is more valuable in the diagnosis and study of AION than FFA . (Chin J Ocul Fundus Dis, 2001,17:111-114)