Abstract
Purpose :
Previous studies suggest nicotinamide (NAM) supplementation may have a beneficial effect on inner retinal function in glaucomatous patients. This masked, randomized study aimed to demonstrate the effect of 7-week NAM supplementation on inner retinal function using electroretinography (ERG) in ADAMTS10-OAG dogs.
Methods :
Ten ADAMTS10-OAG dogs (6 females & 4 males; median age: 4.3 yrs, range: 4.1-6.6 yrs) were enrolled. Five dogs (Group 1) were supplemented orally with 1,500 mg NAM daily. The other 5 dogs served as controls (Group 2) and received sham treatment. Photopic full-field ERGs were recorded at baseline, treatment weeks 5 & 7, and at 13 weeks (washout) using red stimulation of varying intensities (0.07, 0.90, 1.74, 2.57, 3.40, 4.00 cd.s/m2) on blue background (25 cd/m2). The following parameters were analyzed for the 4.00 cd.s/m2 stimulation: b-wave amplitude and implicit time, photopic negative response (PhNR) amplitude and implicit time, and PhNR/b-wave amplitude ratio. Weekly diurnal intraocular pressures and ophthalmic & physical exams were performed. Data were compared between groups using a repeated measures design, fitting a linear mixed model while controlling for baseline measurements.
Results :
Treatment groups were found to be balanced and adequately randomized on baseline characteristics, such as age, pupil size, intraocular pressure, and sex. There was no detectable significant treatment effect of NAM for any of the tested ERG parameters. After 7 weeks of supplementation, the following values were obtained (mean ± SD) for treatment Group 1 vs control Group 2: b-wave amplitude, 15.8 ± 5.4 vs 29.7 ± 6.7 µV; b-wave implicit time, 31.9 ± 1.0 vs 30.5 ± 0.7 ms; PhNR amplitude, 18.7 ± 7.0 vs 22.8 ± 7.7µV; PhNR implicit time, 43.6 ± 3.7 vs 44.1 ± 2.1 ms; and PhNR/b-wave amplitude ratio, 1.3 ± 0.6 vs 0.8 ± 0.2.
Conclusions :
Short-term NAM supplementation at selected standard doses did not result in a noticeable improvement of inner retinal function in the well-established, clinically relevant large animal OAG model. Larger sample sizes and longer treatment duration may be needed to enhance function in glaucomatous eyes and detect a neuroprotective effect.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.