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An unusual experimental treatment for fading sight involves shining a red light into the eyes for a few minutes to boost the activity of mitochondria, microscopic structures that provide energy inside cells.
In the first small test of the approach in 24 people, one short exposure to the light slightly improved people’s performance in tests of colour vision for several days.
Deep red light and near-infrared light have previously been shown to enhance the function of mitochondria in a range of cell-based and animal experiments. These wavelengths seem to work by improving the performance of key molecular structures within mitochondria, called ATP synthase pumps.
These pumps manufacture a molecule called ATP, which cells use for energy, by rotating within the watery environment of the mitochondria. Deep red light has just the right wavelength, at 670 nanometres, to be absorbed by water molecules, which gives them more energy.
This makes the water surrounding each pump less viscous, letting the structure rotate faster. “It is like heating up jam to make it easier to stir,” says Glen Jeffery at University College London.
Although making cells more energy efficient could affect a wide range of bodily systems, Jeffery’s group has been investigating cells of the retina, a patch of light-sensitive tissue at the back of the eye, as they are packed with more mitochondria than any other cell in the body. Impaired mitochondria may contribute to declining eyesight with age and have been implicated in several causes of blindness.
Previous work in flies suggested that mitochondria make most ATP in the mornings. So Jeffery’s group carried out a trial of red light exposure in people aged 37 to 70, comparing treatment in the morning with that given in the afternoon, as a control group.
The participants had a weak deep red light shone at their eyes for 3 minutes. Three hours later, their colour vision was tested by asking them to try to detect letters shown on a similar-coloured background. The team focused on colour vision because the cells in the retina responsible for black and white vision tend to die with age.
When people received one treatment, between 8am and 9am, their performance on the colour contrast test improved by 12 to 17 per cent, compared with before the treatment. Ten members of the group were also tested one week later and their results were still up to 10 per cent better. But there was no significant change if the treatment was done in the afternoon.
Some individuals said they didn’t notice any improvement in their vision, despite performing better on the test, says Jeffery.
Louise Gow at UK charity the Royal National Institute of Blind People says the findings are exciting, but a bigger study is needed to see if the approach can bring noticeable benefits to people’s vision. “A larger study would establish the evidence for this type of innovative treatment,” she says.
The treatment may help in diverse conditions because boosting mitochondria “turns on all the systems in the cell that make the cell work better”, says Janis Eells at the University of Wisconsin-Milwaukee. Eells is working with a firm called LumiThera, which markets a red light device for treating macular degeneration in some countries.
Various groups have also shown that shining deep red or near-infrared light on the head can improve the condition of animals used to model brain injuries and conditions, such as stroke and Parkinson’s disease, in lab experiments.
Jeffery’s group has also found that red light irradiation can protect bees exposed to neonicotinoid insecticides, which damage mitochondria. The group proposes that beekeepers put lamps in their hives.