Improvement in inner retinal function in glaucoma with nicotinamide (vitamin B3) supplementation: A crossover randomized clinical trial.

Importance: 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. However, the potential of nicotinamide in human glaucoma is unknown.

Background: To examine the effects of nicotinamide on inner retinal function in glaucoma, in participants receiving concurrent glaucoma therapy.

Design: Crossover, double-masked, randomized clinical trial. Participants recruited from two tertiary care centres.

Participants: Fifty-seven participants, diagnosed and treated for glaucoma.

Methods: Participants received oral placebo or nicotinamide and reviewed six-weekly. Participants commenced 6 weeks of 1.5 g/day then 6 weeks of 3.0 g/day followed by crossover without washout. Visual function measured using electroretinography and perimetry.

Main Outcome Measures: Change in inner retinal function, determined by photopic negative response (PhNR) parameters: saturated PhNR amplitude (Vmax), ratio of PhNR/b-wave amplitude (Vmax ratio).

Results: PhNR Vmax improved beyond 95% coefficient of repeatability in 23% of participants following nicotinamide vs 9% on placebo. Overall, Vmax improved by 14.8% [95% CI: 2.8%, 26.9%], (P = .02) on nicotinamide and 5.2% [-4.2%, 14.6%], (P = .27) on placebo. Vmax ratio improved by 12.6% [5.0%, 20.2%], (P = .002) following nicotinamide, 3.6% [-3.4%, 10.5%], (P = .30) on placebo. 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).

Conclusions: Nicotinamide supplementation can improve inner retinal function in glaucoma. Further studies underway to elucidate the effects of long-term nicotinamide supplementation.