Purpose : The retina declines both structurally and functionally with age, with mitochondria playing a key role. Red to near-infrared (R-NIR) light in the region of λ670nm improves mitochondrial function and has been associated with improvements in color contrast sensitivity in preliminary studies of human retinal aging. This study tests the hypothesis that R-NIR light improves retinal cone system function in participants aged over 30 years, using a randomized controlled experimental design.
Methods : Volunteers aged 30-73 years with normal color vision were randomized to receive a R-NIR intervention (λ670nm, n=12) or green light control (λ535nm, n=14). Participants and investigators were masked to group allocation. The devices produced non-coherent light (1mW/cm2) via light-emitting diodes (LEDs), of lower energy than in previous studies, and were self-applied to the eye for 90 seconds. Monocular color contrast sensitivity (CCS) was measured along tritan and protan axes to investigate S- and L-cone-mediated color vision respectively. Monocular Farnsworth-Munsell 100 hue test (FM100) scores were divided into ‘blue-yellow’ and ‘red-green’ to measure S- and L-/M-cone-mediated color vision respectively. Outcomes were measured at baseline and 3 hours post-exposure and assessed for improvement using a 1-tailed paired t-test. Outcome measures were compared using multiple linear regression to adjust for baseline differences.
Results : Tritan thresholds improved by 15% after 670nm exposure (p=0.0015), consistent with a 17% improvement in ‘blue-yellow’ FM100 scores (p=0.0268). There was no change in protan thresholds or ‘red-green’ FM100 scores after 670nm exposure, and no mean change in any metric in the control group. When compared to control, there was weak evidence that 670nm improved tritan thresholds (p=0.18) and ‘blue-yellow’ FM100 scores (p=0.21).
Conclusions : There is evidence of improvement in S-cone-mediated color vision following a single short exposure to low level 670nm light. The study raises the possibility that weak R-NIR exposure may promote cone function pertinent to healthy retinal aging.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.
