A short burst of red light in the morning has been shown to improve declining eyesight, researchers report, potentially providing a simple, safe, and easy-to-use treatment for keeping our eyes sharper as we head into old age.

In tests on 20 participants exposed to three minutes of 670 nanometer deep red light in the morning between 8 am and 9 am eyesight improved by 17 percent and lasted (at a lower level) a week on average. In some of the volunteers, the improvement was as much as 20 percent.

This link between long wavelength red light and improving vision matches up with what scientists have seen in previous studies on animals, and the study follows on from a similar one carried out last year – but in this case, the red light was limited to a single, daily exposure that required less red light energy than previously.

"Using a simple LED device once a week recharges the energy system that has declined in the retina cells, rather like recharging a battery," says neuroscientist Glen Jeffery from University College London (UCL) in the UK.

"And morning exposure is absolutely key to achieving improvements in declining vision: as we have previously seen in flies, mitochondria have shifting work patterns and do not respond in the same way to light in the afternoon – this study confirms this."

The mitochondria in the eye, often called the cell's powerhouses, are key: The team already knew that they're more receptive in the morning, and it's these organelles that the red light is recharging so that they can produce more energy.

Photoreceptors in the retina, where mitochondria are collected most densely, are made up of cones (handling color vision) and rods (for adapting to low light). Here the team focussed on cones, assessing color contrast sensitivity after exposure to the red light.

Follow-up tests on six participants, using red light treatment daily between 12 pm and 1 pm, didn't result in any change in vision – confirming that mitochondria aren't as responsive to deep red light in the same way later on in the day.

RedLightEyeTreatment (University College London)

Above: Dr. Pardis Kaynezhad holds a deep red light over her eye, which helps stimulate the mitochondria in her retinal cells.

"Mitochondria have specific sensitivities to long wavelength light influencing their performance," says Jeffery. "Longer wavelengths spanning 650 to 900 nanometers improve mitochondrial performance to increase energy production."

Cells in the human retina start to age once we reach the age of 40 or so, and that aging is caused in part by the slowing down of the mitochondria power supplies. As the retina's photoreceptors require more energy, they tend to age faster as well.

The simple, low-energy LED device used in the study may be an affordable eyesight treatment that people could quickly apply. It's probably safe to use, too, as 670 nanometer infrared light isn't much different from light found in the natural environment.

Developing a finished device for widespread use will take some time, however, and the researchers do caution that some of their data is "noisy": the level of improvement did vary between participants, even those of similar age. Future studies could look more closely at other variables that might be influencing the results.

"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," says Jeffery.

The research has been published in Scientific Reports.