EPO and optic neuritis: Suhs et al demonstrated lower RNFL thinning and lower values of visual evoked potential parameters in patients with optic neuritis when they received 33,000 units/day of intravenous erythropoietin for three days as an add-on therapy to methylprednisolone compared to those who received only methylprednisolone.[14] The aforementioned studies favored the structural and physiological effects of erythropoietin in treating optic neuritis.