This randomized double-blind clinical trial is performed on all recent (within the last 5 days) NAION patients referred to hospitals affiliated to the Shahid Beheshti University of Medical Sciences, Iran. The patients will be equally and randomly assigned into two experimental groups and a control group. The first experimental group will receive 1000 units of erythropoietin every 12 hours for three days. The second experimental group will receive 50 mg of oral prednisolone from the onset of the disease for 1 week, with the dose gradually reduced within 2 weeks and then discontinued. In addition, the subjects in the second experimental group will receive 300 mg of ranitidine daily. The third group will receive placebo. Eye examination with color vision, perimetry, and peripapillary optical coherence tomography (to measure the thickness of the retinal nerve fiber layer) will be performed before the intervention, and 1, 3 and 6 months after the intervention. SITA standard visual field testing will be done using the Visual Field Analyzer Humphrey 750 Field (Carl Zeiss, USA). The thickness of the retinal nerve fiber layer will be measured by optical coherence tomography (Cirrus Zeiss Cirrus HD-OCT, Carl Zeiss, USA). The q-q plot and Kolmogorov-Smirnov tests will be performed to test normal distribution of data. Descriptive statistics including frequency, percentages, standard deviation, median and range will be used. Other statistical test including ANOVA, Kruskal-Wallis, Chi-Square, and Fischer's exact tests will be performed. All statistical analyses will be performed in SPSS (version 20) at significance level of 0.05.

Inclusion criteria:

- All NAION patients (maximum time of disease occurrence: 5 days) referred to emergency department of Labbafinejad, Torfeh and Imam Hossein hospitals

Exclusion criteria:

1. Glaucoma or any ocular, neurologic or systemic disease affecting the vision
2. Abnormal laboratory test results such as ESR and CRP
3. History of ocular surgery
4. History of receiving medication for NAION
5. Uncontrolled systemic disease such as diabetes or hypertension
6. Contraindications of systemic steroids including active infection, active gastric ulcer, immunosuppression
7. Contraindications of erythropoietin administration, such as polycythemia
8. Unwillingness to participate in the study