Deep red light exposure improves declining eyesight

Exposing the eyes to three minutes of deep red light once a week can significantly improve declining eyesight – but only if it is done in the morning.

A study by researchers at University College London says this could lead to affordable home-based eye therapies to help stem naturally declining vision.

They found an average 17% improvement in participants’ colour contrast vision when exposed to three minutes of 670 nanometre deep red light in the morning and the effects of this single exposure lasted for at least a week.

However, when they conducted the same test in the afternoon, the researchers noted no improvement.

The study, published in the latest edition of Scientific Reports, builds on UCL’s previous work that demonstrated three-minute daily exposure to long wave deep red light “switched on” energy-producing mitochondria cells in the human retina, which boosted naturally declining vision.

This time, they wanted to establish what effect a single three-minute exposure would have, while also using lower energy levels than the previous studies.

Professor Glen Jeffery, lead author from UCL Institute of Ophthalmology, said: “We demonstrate that one single exposure to long wave deep red light in the morning can significantly improve declining vision, which is a major health and wellbeing issue, affecting millions of people globally.

“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.”

The previous study in mice, bumblebees and fruit flies found significant improvements in the function of the retina’s photoreceptors when their eyes were exposed to 670 nanometre deep red light.

This study focused on cones and observed colour contrast sensitivity, along the protan axis, measuring red-green contrast, and the tritan axis, blue yellow.

It recruited 20 participants – 13 female and seven male – all aged between 34 and 70, all with normal colour vision and none of whom had ocular disease.

They also completed a questionnaire about their eye health.

Each was given an LED device and they were exposed to three minutes of 670nm deep red light between 8am and 9am.

The light energy emitted by the LED torch was 8mW/cm2, rather than 40mW/cm2 that had been used previously.

The participants’ colour vision was then tested again three hours post exposure and 10 of the participants were also tested one week post exposure.

On average there was a 17% improvement in colour vision, which lasted a week in tested participants, while in some older participants there was a 20% improvement, which also lasted a week.

A few months after the first test, three of the female participants and three males carried out the same test in the afternoon, but no improvement was recorded.

Prof Jeffery said: “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.

“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.”

He added that because the technology is simple and safe, he was confident an affordable, easy-to-use device could be made.

“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,” added Prof Jeffrey.

The researchers caution that despite the positive results, the magnitude of improvements can vary markedly between those of similar ages, which means the data need to be interpreted carefully.

Shinhmar H, Hogg C, Neveu M et al. Weeklong improved colour contrasts sensitivity after single 670nm exposures associated with enhanced mitochondrial function. Scientific Reports 24 November 2021; doi: 10.1038/s41598-021-02311-1


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