Purpose: To assess changes in visual field (VF) values after gene therapy for Leber’s hereditary optic neuropathy (LHON). Methods: VF recovery, VF indices, and mean deviation in injected and uninjected eyes, before and after gene therapy, were examined in 2 groups of patients according to disease duration (≤2 years and > 2 years). Nine patients with LHON were treated by monocular intravitreal injection of AAV2-ND4. Finally, 7 patients were considered for subsequent comparisons; the first and second eyes were treated separately. Results: There were no significant differences in VF indices and mean deviation between injected and uninjected eyes (p = 0.910 and p = 0.929, respectively). However, there was a significant difference before and after injection (p = 0.016 and p = 0.015, respectively). There was no significant difference in VF improvement between patients with ≤2 years’ disease duration and those with a longer disease duration. Conclusion: There was a statistically significant VF improvement after gene therapy. This suggests that monocular intravitreal injection of AAV2-ND4 can improve binocular VF values. This study also suggests that gene therapy can be effective in patients with a disease duration of > 2 years.