Red Light Therapy May Refresh Retinal Photoreceptor Function in Older Adults

By Lisa Rappaport

July 24, 2020

(Reuters Health) - Older adults exposed to red light therapy may experience improvements in cone color contrast sensitivity and rod sensitivity, according to results from a small experiment that suggest a way of improving certain forms of age-related visual decline.

Mitochondrial density is greatest in the retina's photoreceptor cells, which have high energy demands, and this leads the retina to age faster than other organs as aging mitochondria produce less energy over time, researchers note in the Journals of Gerontology: Series A. Based on previous studies in mice, bees, and fruit flies, researchers hypothesized that they might see improved retinal function in humans after exposure to 670 nanometers (nm) deep red light.

Researchers asked 24 people ranging in age from 28 to 72 years with no history of ocular disease to expose their dominant eye to 670 nm of red light once daily for three minutes in the morning for two weeks. Researchers tested rod and cone sensitivity at baseline and again after two weeks of red light exposure.

Half of the participants were under 40 years old, and red light exposure didn't alter their test results for rod and cone sensitivity. But among the older participants, cone color contrast sensitivity improved by up to 20% and rod sensitivity also improved, although the change was not as pronounced.

"Mitochondria drive aging when their energy supply runs down," said senior study author Glen Jeffery, a professor of neuroscience at University College London in the UK.

"They happen to absorb long wavelength light, and with the right metrics and you can use this to recharge the battery and increase the energy they provide the cell with," Jeffery said by email.

Beyond its small size, another limitation of the study is that researchers didn't follow participants after the experiment ended to observe the duration of any improved visual function. Results might also be different among people with ocular diseases, a group excluded from the experiment.

"This is the first study to show that human retinal function also declines with age and that far-red light treatment protects against the reduction of rod and cone photoreceptor function in the human retina as it does in experimental animals," said Janis Eells, a professor of biomedical sciences at the University of Wisconsin-Milwaukee who wasn't involved in the study. Eells is a scientific advisor for two photo medicine companies, LumiThera and MultiRadiance Medical.

Aging is the primary risk factor for major retinal diseases including age-related macular degeneration (AMD), glaucoma and diabetic retinopathy, Eells said by email.

"This study documents the loss of photoreceptor function with aging in the healthy human eye," Eells said. "The application of far-red light to enhance mitochondrial performance has great potential in moderating the aging process in this metabolically demanding tissue."

SOURCE: Journals of Gerontology: Series A, online June 29, 2020.