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Red light revolution

Brief daily exposure to deep red light could improve declining vision in older adults

Priscilla Lynch

Posted: Thursday, October 1, 2020


Glen Jeffery PhD

Could simply staring at a deep red light regularly help slow or reverse age-related visual decline?

Yes, according to a first-in-human study recently published in the Journals of Gerontology, which showed that daily three-minute exposure to a specific light wavelength for two weeks significantly improved retinal function in those aged over 40 years of age.

Speaking to EuroTimes, lead study author Prof Glen Jeffery PhD, University College London Institute of Ophthalmology, explained that the retina consumes more energy than any other part of the body; mitochondrial density is greatest in photoreceptors, particularly cones that have high energy demands and mediate colour vision.

Thus the retina ages faster than other organs and at around 40 years-old retinal ageing accelerates, leading to a significant decline in photoreceptor function and consequently vision deterioration.

Mitochondria have specific light-absorbance characteristics influencing their performance. Longer wavelengths spanning 650->1,000 nanometres (nm) have been found to improve mitochondrial complex activity, membrane potential and energy production in the form of ATP. So exposing eyes to a red-light source of a long wavelength, which is absorbed by mitochondria in the retina, could therefore rejuvenate photoreceptor function and improve declining vision, explained Prof Jeffery.

This hypothesis was tested successfully by his team in a number of animal model studies (in aged flies, bumblebees and mice), which recorded significant improvements in retinal photoreceptor function when the animal eyes were regularly exposed to 670nm (long wavelength) deep red light over relatively short time periods.

For this human study, 24 people (12 male, 12 female), aged between 28 and 72 years, who had no ocular disease, were recruited. All participants’ eyes were tested for the sensitivity of their rods and cones at the start of the study. Rod sensitivity was measured in dark-adapted eyes (with pupils dilated) by asking participants to detect dim light signals in the dark, and cone function was tested by subjects identifying coloured letters that had very low contrast and appeared increasingly blurred.

All participants were given a small LED torch to take home to look into its deep red 670nm light-beam for three minutes a day for two weeks. They were then re-tested for their rod and cone sensitivity.

The 670nm light had no impact in younger individuals, but in those around 40 years and over, significant improvements were obtained. In the tritan axis, baseline cone colour contrast sensitivity increased significantly in those about 40 years or older compared to younger subjects by maximum of around 20%.

Improvements were more significant in the blue part of the colour spectrum that is more vulnerable in ageing.

Rod sensitivity also improved significantly in those aged around 40 and over, though less than colour contrast.

“We’ve basically shown that deep red-light wavelengths can recharge the energy system that has declined in the retina cells, rather like re-charging a battery,” Prof Jeffery told EuroTimes.

He now plans further larger scale, longer studies, as well as working on bringing a financially accessible, evidenced-based version of this simple light technology to market.

“We had some people’s retinal function improve by 20%, others by about 5% and we’d love to know why. While the improvement was not immediately obvious, two people in this study, who were unaware of what we were testing for, mentioned that colours seemed clearer so that was interesting.

“We also know now since we completed this study that we can get this to work with perhaps a couple of exposures a week, and the effect will last for about three to four days so there are plenty more avenues of research to explore.”

RETINAL DISEASE USES?
Would the technology have any potential in the treatment of retinal diseases like age-related macular degeneration (AMD)? “We tried it in AMD and it didn’t work. But we looked at why that was, and now have a clear idea of the reasons. Firstly, it was because we only ran it for a year and AMD is a really slow disease; whereas the control group did really well,” Prof Jeffery noted.

Moreover, the tested AMD patients had advanced disease, a number of whom had begun to develop geographic atrophy. “So we need to start earlier with such patients, and in those with more advanced disease we need to assess them over a longer period of time because our prediction is that if we measure the spread of geographic atrophy it will be slower [in those using the light technology], but that will require significant funding.”

For now, Prof Jeffery is excited about the broad potential of this safe, cheap light technology to potentially slow and partially reverse age-related visual loss in the global population.

“The key issue for me is that everybody gets old. Not everybody gets an eye disease.”

Glen Jeffery: g.jeffery@ucl.ac.uk