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Disclaimer – the following information is for educational purposes only and Red Light Rising does not recommend using red light therapy on your eyes without first speaking to your eye specialist.
In this blog we are going to cover the latest study on red light therapy and eye health. Published the 24th of November in the prestigious journal, Nature.
Metabolic rate and aging are both regulated by mitochondria, which are cell organelles present in all human cells.
Mitochondrial membrane potential, however, declines with age resulting in reduced adenosine triphosphate (ATP) production, which is a major source of cellular energy.
Retinal photoreceptors, present in the eye, have the greatest mitochondrial density and metabolic demand in the body and age rapidly, starting it’s decline around age 40.
In animal studies exposure to long wavelength light (650–900 nm) showed improvement in mitochondrial function, increasing ATP production and reducing the pace of age related cell death in the retina.
While few human experiments have been undertaken with long wavelength light in aging, daily exposure to relatively bright 670 nm light over weeks in aged humans has been demonstrated to improve rod and cone function in the eye. But we have no knowledge of how much exposure is needed and how long its influence persists.
With all these variables in mind, the following study published in Nature was conducted.
The study was conducted in accordance with the Declaration of Helsinki and approved by the UCL research ethics committee (16547/001). Each participant provided written informed consent prior to testing.
Subjects were healthy, of both sexes with an age range of 34–70 years. Each had normal colour vision and were given a general questionnaire regarding eye health prior to testing.
All exposures to 670 nm were for 3 min to the subjects’ dominant eye either in the morning between 8 and 9 AM or the afternoon between 12 and 1 PM and were assessed at either 3h post exposure or 1 week later without further 670 nm exposure in the intervening period.
However, an additional control was undertaken where colour contrast thresholds were measured in the morning and then re-measured 3 h later without exposure to 670 nm. To determine if there were significant shifts in colour contrast sensitivities across the day that were independent of 670 nm and might undermine outcome measures for their exposure, six subjects were repeatedly tested at 0, + 3, + 6 and + 9 h.
Subjects were seated at a fixed distance from the stimulus monitor so that that opto-type letter subtended a 1.3-degree angle on the retina.
All results were taken in triplicate and analysed from initial baseline recordings and final recordings taken after 670 nm exposure at the indicated time points.
The data that support the findings of this study are available on request from the corresponding author GJ. The data are not publicly available due to them containing information that could compromise research participant privacy.
A single 3min session with the 670 nm light in the morning (8-9AM) significantly improved subject colour contrast thresholds for both tritan and protan axes when tested 3h later.
If we divide the population that took part in the study by progressive age, in those between 38-49 years it improved 14%, in those 50-59 it improved 20%, in those 60-79 it improved 19%.
They tested the same treatment in the afternoon and the results showed no impact across either colour axis following afternoon light exposure. Hence only the morning light dose is effective.
Time of exposure is critical, as 670 nm light is only effective in the morning. This time dependent effect is likely due to the demonstrated shift in mitochondrial function across the day, and light exposure is likely only effective when synchronised to an aspect of this process.
Single exposures to 670 nm light delivered in the morning, has the ability to improve cone photoreceptor function in aged subjects to levels commonly found in much younger individuals and can be sustained for up to a week.
The subject population was ≥ 35 years because they have previously shown that the impact of 670 nm light on retinal function is reduced in younger subjects, presumably due to the relatively healthy state of their retinal mitochondria. This is consistent with the mitochondrial theory of ageing.
The study concludes that a single 3-minute exposure to 670 nm light can significantly improve color contrast sensitivity in people aged between 37 and 70.
This improvement brings their color contrast sensitivity to levels typically seen in younger individuals.
Importantly, the light exposure needs to be in the morning to be effective.
The enhanced color vision can last up to a week after just one exposure.
This finding suggests a simple and cost-effective way to improve the quality of life for older people, particularly those experiencing vision problems.
Shinhmar, H., Hogg, C., Neveu, M. et al. Weeklong improved colour contrasts sensitivity after single 670 nm exposures associated with enhanced mitochondrial function. Sci Rep 11, 22872 (2021). https://doi.org/10.1038/s41598-021-02311-1