Nicotinamide riboside as a neuroprotective therapy for glaucoma: study protocol for a randomized, double-blind, placebo-control trial.

BACKGROUND: Whereas lowering the intraocular pressure (IOP) can slow optic nerve degeneration in glaucoma, many patients with glaucoma continue to develop progressive loss in vision despite a significant reduction in IOP. No treatment has been shown to be effective for neuroprotection in glaucoma. We set out to conduct a randomized controlled trial to investigate whether nicotinamide riboside (NR), a nicotinamide adenine dinucleotide precursor, is effective to slow optic nerve degeneration in patients with primary open-angle glaucoma (POAG). We hypothesize that patients treated with NR have a slower rate of progressive retinal nerve fiber layer (RNFL) thinning compared with those treated with placebo. METHODS: This is a randomized, double-blind, placebo-controlled, parallel-group, multi-center study including 125 patients with POAG. Patients will be randomized to receive 300 mg NR or placebo for 24 months. Clinical examination, optical coherence tomography imaging of the RNFL, and visual field (VF) test will be performed at the baseline, 1 month, 4 months, and then at 2-month intervals until 24 months. The primary outcome measure is the rate of RNFL thinning measured over 24 months. The secondary outcome measures include (1) time to VF progression, (2) time to progressive RNFL/ganglion cell inner plexiform layer (GCIPL) thinning, and (3) the rate of change of VF sensitivity over 24 months (to investigate neuroprotection) and 1 month (to investigate neuroenhancement). The rates of RNFL thinning and VF sensitivity decline between treatment groups will be compared with linear mixed modeling. Survival analysis will be performed to compare the differences in time from baseline to VF progression and time from baseline to progressive RNFL/GCIPL thinning between treatment groups using Cox proportional hazards models. DISCUSSION: Outcome measures in glaucoma neuroprotection trials have been centered on the detection of VF progression, which may take years to develop and confirm. In addition to addressing whether NR has a neuroprotective/neuroenhancement effect in glaucoma patients, this study will demonstrate the feasibility of studying neuroprotection in a relatively short trial period (24 months) by comparing the rates of progressive RNFL thinning, a more reproducible and objective outcome measure compared with VF endpoints, between treatment groups. TRIAL REGISTRATION: Chinese Clinical Trial Registry 1900021998.

Progression of Macular Vessel Density in Primary Open-Angle Glaucoma: A Longitudinal Study.

PURPOSE: To evaluate the rate of progression of macular vessel density (mVD) in primary open-angle glaucoma (POAG) and explore the relationship between the progression of mVD and macular ganglion cell-inner plexiform layer (mGCIPL) thickness and parapapillary retinal nerve fiber layer (pRNFL) thickness. DESIGN: Prospective cohort study. METHODS: In this study, 102 eyes with POAG were followed for 36.6 ± 6.4 months. The rates of progression were estimated by linear models. The agreement of progression detection among the 3 parameters was evaluated with Kappa statistics. The influence of baseline measurements on the rates of progression of mGCIPL thickness, pRNFL thickness, and mVD was investigated by linear mixed modeling. Kaplan-Meier survival analysis was adopted to calculate the survival probabilities. RESULTS: The respective rate of progression by linear regression was -0.102 ± 0.054 µm/month, -0.160 ± 0.086 µm/month, and -0.199 ± 0.073 %/month for mGCIPL thickness, pRNFL thickness, and mVD. The agreement in detection of progression among them was poor with the Conger's Kappa coefficient of 0.098 (95% confidence interval: -0.025~0.220, P = .116). The significant factors influencing the rate of progression of mVD were baseline mGCIPL thickness, baseline pRNFL thickness, and baseline mVD (P ≤ .001), while baseline mVD was not a significant factor influencing the rates of progression of mGCIPL thickness and pRNFL thickness (P ≥ .659). Also, pRNFL thickness had a better survival probability compared with the other 2 parameters (P = .025). CONCLUSIONS: The mGCIPL thickness, pRNFL thickness, and mVD decreased over time in POAG eyes. The rate of reduction of mVD was significantly influenced by the baseline measurements of mGCIPL thickness, pRNFL thickness, and mVD.