Seeing Red: Morning Exposure to Deep Red Light Supports Eyesight and Color Vision

Unlike the times of our tech-free ancestors, our modern world is inundated with artificial lighting everywhere we look. Seemingly uninterrupted, we experience fluorescent lights blaring at work, constant glows emanating from our various smart devices, and household lamps keeping us up well past sundown. The cost of this constant bombardment of light is that certain parts of our eyes have become undeniably lazy because they just aren’t needed like they were in our pre-electricity days.

Despite the obvious advantages of being able to see clearly at all hours of the day and night, there are a few downsides — including losing the function of specialized cells in our eyes called rods. With this loss comes an overreliance on other cells in the eye, causing them to decline in function and contribute to various types of vision loss that affect millions of people worldwide. Now, researchers from the University College London have uncovered an effective way to combat these losses — a once-per-week 3-minute exposure to deep red wavelength light. In this novel study published in the journal Scientific Reports, Shinhmar and colleagues show how this simple intervention improves color vision in adults, which could be revolutionary for supporting eye health as we age.

The Nuts and Bolts of Rods and Cones

Two types of photoreceptors — specialized cells for detecting light — line the retina needed for vision. Rods are responsible for night vision, while cones enable us to see and contrast colors in the daylight. In our artificially lit world, the underuse of rods causes about one-third of them to die off starting around age 40, making our eyes overly reliant on cone function. While cones don’t experience the same cell death that rods do, they can have a sharp decline in functionality as we age, especially when overworked. 

These retinal photoreceptors have the highest metabolic demand in the body, requiring the greatest density of mitochondria, our cells’ energy production centers. However, this high metabolic demand comes with a price — increased production of harmful compounds called reactive oxygen species (ROS), which accelerate aging and contribute to mitochondrial dysfunction. Therefore, researchers are looking for ways to support mitochondria in the retina as a way to improve cone function and vision as a whole — and short exposure to a wavelength of deep red light could be an answer.

Previous research has found that exposing animals to long-wavelength light improves mitochondrial function, increases ATP (energy) production, fights ROS buildup, and delays aging and cell death in the retina. However, few studies have looked at how different light wavelengths affect human retinal photoreceptor health and vision — and how much (or little) exposure is needed to see results.

They Can See Clearly Now: 3 Minutes of Red Light Boosts Color Vision

In this study, Shinhmar and colleagues tested the effects of red light exposure (specifically, 670 nanometre [nm], long-wavelength deep red light) in a group of adults aged 34 to 70 without color blindness. The research team assessed their cone function using a test that asked them to identify colored letters with very low contrast that appear increasingly blurred, a process known as color contrast. 

The results were striking — just three minutes of red light therapy in the morning significantly boosted their color contrast thresholds when tested both three hours and one week later. Although the effects were most robust on the same day, there were still significant improvements holding strong one week later. 

They also looked at the function of specific cone types. The “tritan” cones in the retina, which differentiate blue and yellow colors, exhibited more benefits (17% improvement) from the deep red light therapy than “protan” cones, which enable the vision and contrast of reds and greens (12%). Plus, more advantages were seen in the older age groups than younger, likely because the younger adults would still have healthier retinal mitochondria. 

Interestingly, only morning exposure to the deep red light exhibited the benefits. When the participants were exposed to the red light in the afternoon or evening, there was no significant impact on either of the cone’s color axes. The researchers speculate that this time-dependent effect is due to a shift in mitochondrial activity, in which these cellular powerhouses follow and respond to a biological circadian rhythm. The mitochondria may be more sensitive and receptive to interventions in the earlier hours of the day, as seen with a study with fruit flies that found energy production to be 40% higher in the morning.

As the senior author of this study, Professor Glen Jeffery, states, "Mitochondria have specific sensitivities to long-wavelength light influencing their performance: longer wavelengths spanning 650 to 900nm improve mitochondrial performance to increase energy production.” 

Things Are Looking Up: A Future of Easy, Affordable Vision Support  

While these results are certainly promising, the authors are cautious that more research is needed, as this was a relatively small sample size of 20 adults. Plus, although there were apparent positive effects, the magnitude of the benefits varied widely, even between those of the same age. 

However, the authors are optimistic that this type of therapy could enormously impact the world. As Dr. Jeffery states, "This simple intervention applied at the population level would significantly impact on quality of life as people age and would likely result in reduced social costs that arise from problems associated with reduced vision.” 

He continues, "Using a simple LED device once a week recharges the energy system that has declined in the retina cells, rather like re-charging a battery…In the near future, a once a week three-minute exposure to deep red light could be done while making a coffee, or on the commute listening to a podcast, and such a simple addition could transform eye care and vision around the world."

And, unlike current LED devices on the market, which are incredibly expensive — some to the tune of $20,000 — Dr. Jeffery and his team hope to produce more affordable deep red-light therapies that could benefit people worldwide. But for now, we’ll have to wait and see.

References: 

Shinhmar H, Hogg C, Neveu M, Jeffery G. Weeklong improved colour contrasts sensitivity after single 670 nm exposures associated with enhanced mitochondrial function. Sci Rep. 2021;11(1):22872. Published 2021 Nov 24. doi:10.1038/s41598-021-02311-1

Sivapathasuntharam C, Sivaprasad S, Hogg C, Jeffery G. Improving mitochondrial function significantly reduces the rate of age-related photoreceptor loss. Exp Eye Res. 2019;185:107691. doi:10.1016/j.exer.2019.107691

Weinrich TW, Kam JH, Ferrara BT, Thompson EP, Mitrofanis J, Jeffery G. A day in the life of mitochondria reveals shifting workloads. Sci Rep. 2019;9(1):13898. Published 2019 Sep 25. doi:10.1038/s41598-019-48383-y