In rodent models with anterior ischemic optic neuropathy (AION), granulocyte colony-stimulating factor (G-CSF) confers a neuroprotective effect on retinal ganglion cells (RGCs) via anti-apoptotic and anti-inflammatory processes. This prospective study investigated the efficacy of intravitreal injection of G-CSF for the treatment of non-arteritic anterior ischaemic optic neuropathy (NAION). Fourteen eyes of 14 patients with acute NAION were enrolled in this prospective interventional case series. They received an intravitreal injection of 60 micrograms in 0.1ml of G-CSF within two weeks of the onset of the disease. Visual acuity, visual field, intraocular pressure (IOP), corneal endothelial cell density, and peripapillary retinal nerve fibre layer (RNFL) thickness were recorded before injections and one week, one month, three months, six months, and one year after the injections. Full-field electroretinography (ERG) was obtained at the baseline, one month, and 12 months post-injections. Results: Best-corrected visual acuity (BCVA) significantly improved in the first month following injections (p=.007), decreased subsequently, and the final BCVA showed no significant improvement (p=.278) compared to the baseline measurements. A significant decrease in RNFL thickness was observed in all quadrants compared to the baseline measurements. Also, no improvement in the visual field parameters was observed. From the toxicity aspect, no significant changes in the corneal endothelial cell density, IOP, and ERG recordings were observed. The authors conclude that intravitreal injections of G-CSF appear safe, however, there was no long-term improvement in visual outcome compared to baseline.