Originally published 2021-11-26.
Can looking at a red light really improve your eyesight? A small 2021 study from University College London (UCL) suggests that one specific kind of light can produce a modest, short-term improvement in one aspect of vision. Twenty volunteers aged 34 to 70 looked into a deep red LED light with a wavelength of 670 nanometres for three minutes between 8 and 9 in the morning. Three hours later, their ability to tell apart low-contrast colours had improved by an average of 17%, and in the ten people retested a week later, the gain was still there. The same exposure around midday did nothing. It is a promising result, but it is not a cure for poor eyesight, and the details matter.
What the UCL study actually found
The research, led by Professor Glen Jeffery of the UCL Institute of Ophthalmology, was published in Scientific Reports in November 2021. Its 20 participants, 13 women and 7 men, had no eye disease and normal colour vision. Each was given a small LED device that emitted deep red light and asked to look into it for three minutes.
The team then measured colour contrast sensitivity using a computer-based "Chroma Test", in which people identify coloured letters that differ only slightly from the background. They looked at two colour axes: protan (red-green) and tritan (blue-yellow). The tritan axis is of particular interest because blue-yellow discrimination tends to decline earliest with age.
After morning exposure, the group's colour contrast scores rose by an average of 17%, and some of the older volunteers improved by around 20%. Months later, after the effect had worn off, six of the participants repeated the experiment between midday and 1pm. This time there was no improvement at all.
Why red light might help ageing eyes
The idea rests on mitochondria, the tiny structures inside cells that turn nutrients into usable energy in the form of adenosine triphosphate (ATP). The retina is one of the most energy-hungry tissues in the body, and its photoreceptors, the rods that work in dim light and the cones that let us see colour and detail, contain large numbers of mitochondria.
The UCL team points out that the retina ages faster than other organs, with ATP production falling by roughly 70% over a lifetime. Natural vision decline usually becomes noticeable from around age 40. Light at long wavelengths, in the deep red and near-infrared range, is thought to be absorbed by part of the mitochondrial machinery, boosting its energy output. Experiments in mice, bumblebees and fruit flies had already shown better photoreceptor function after exposure to 670nm light.
One correction is worth making to how the study was often described: ATP is a molecule, not a type of cell. The hypothesis is that red light helps the existing mitochondria in cone cells produce more ATP, so the cones work more efficiently.
Why the morning seems to matter
The timing finding was the headline of the 2021 paper. Earlier UCL work on fruit flies, published in 2019, found that mitochondria have shifting workloads across the day and respond differently to light depending on the hour. The human study appears to fit that pattern: the same dose of light produced an effect in the morning and none around midday.
Jeffery's own summary in the UCL announcement was upbeat:
"One single exposure to long wave deep red light in the morning can significantly improve declining vision."
He also suggested that, in future, a weekly three-minute session might fit easily into a morning routine. That is a hope for the future, not a tested treatment plan.
How this builds on earlier research
The 2021 study followed a 2020 UCL pilot, published in the Journals of Gerontology, in which volunteers looked into a red light device for three minutes every day for two weeks. That trial also reported better colour vision in people whose eyesight had started to decline with age. Popular coverage at the time sometimes quoted very large percentage gains; such numbers came from small groups and should be read with caution until larger trials confirm them.
The newer study also lowered the light dose. Earlier work used 40 milliwatts per square centimetre; the 2021 trial used just 8 mW/cm², with the same wavelength. Both levels were described by the researchers as safe for the eye, and the lower dose produced a clear effect.
The limits: what this study does not show
- It was small. Twenty people is a pilot-sized sample, and only ten were retested after a week and six in the afternoon comparison. The authors themselves noted that some data were "noisy" and that results varied widely between people of similar ages.
- It measured one thing. The study tested colour contrast sensitivity in cones. It did not measure sharpness of vision, the kind tested on an eye chart, and it did not show that glasses could be thrown away.
- It was not a disease treatment. Volunteers had healthy eyes. The results say nothing about cataracts, glaucoma, diabetic eye disease or macular degeneration.
- There was no placebo group. Each person served as their own comparison, which is useful but weaker than a randomised, sham-controlled trial.
Common myths and practical takeaways
Myth: any red lamp will do. The effect was tied to a narrow wavelength around 670nm and a measured energy level. A red bulb, a phone screen set to red or a cheap party light is not the same thing.
Myth: staring at bright light is harmless. Very bright light sources, including some high-powered LED and laser devices sold online, can damage the retina. Eye specialists have warned about poorly regulated light products, so it is wise to be cautious about home devices that make big claims.
Myth: this is a proven treatment. Not yet. Larger trials are needed to confirm the size of the effect, how long it lasts and who benefits. Jeffery said he was working with a small UK company, without commercial gain, on affordable 670nm devices, in contrast to some expensive systems on the market.
For now, the most reliable ways to protect ageing eyes remain the familiar ones: regular eye tests, wearing sunglasses outdoors, not smoking, managing blood pressure and blood sugar, and a diet rich in leafy greens and colourful vegetables. Anyone with changes in vision, or curious about trying red light therapy, should talk to a doctor or optometrist first.
Sources: UCL News (24 November 2021): Morning exposure to deep red light improves declining eyesight; Scientific Reports (2021): the UCL study paper; IFLScience.
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