"AIM:To study the role of indocyanine green angiography(ICGA) in differential diagnosis between nonarteritic anterior ischemic optic neuropathy (NAION) and optic neuritis. METHODS:Twenty-seven cases 27 eyes with detailed clinical data which were not easily diagnosed by optic disc edema on fundus photography were enrolled. All eyes received examination using the retinal and choroidal angiography(FFA and ICGA). The gender and age matched 20 cases 20 normal control eyes received FFA and ICGA over the same period, and continuous images of each group were analyzed. RESULTS:In 20 cases of control eyes,ICGA examination showed early peripapillary choroidal vascular fluorescence filling in normotension. The performance characteristics of early continuous ICGA pictures from the other 27 eyes showed that the optic disc edema can be clearly divided into ischemic and non-ischemic; ischemic images demonstrated a temporary disc ischemia area and the corresponding choroidal regional hypo-fluorescence, from which the scope and extent of ischemia can be directly determined and the 16 eyes were considered to have NAION; 11 eyes with images demonstrating immediately vascular fluorescence filling in normotension in showed the same as normal control and they were considered to have optic neuritis. CONCLUSION:Some of the optic disc edema is difficult to diagnosis accurately. Choroidal angiography showed that there is a disc choroidal regional fluorescein filling defect for NAION with characteristic changes. These changes contribute to the differential diagnosis and are worthy of attention.