Retinal ganglion cells endure significant metabolic stress in glaucoma but maintain capacity to recover function. Nicotinamide, a precursor of NAD+, is low in serum of glaucoma patients and its supplementation provides robust protection of retinal ganglion cells in preclinical models. ...A trend for improved visual field mean deviation was observed with 27% improving ≥1 dB on nicotinamide and fewer deteriorating (4%) compared to placebo (P = .02). Nicotinamide supplementation can improve inner retinal function in glaucoma. Further studies underway to elucidate the effects of long-term nicotinamide supplementation.