Red light therapy for myopia: promises and doubts about safety

A tabletop device, at home. The child looks into it at a red light for three minutes; a few hours later, does it again. In studies red light against myopia was used like this, twice a day, every day or five days a week^2,5.

It is repeated low-level red-light therapy: one of the first large studies on myopic children began in 2019¹. In the short term the results are very clear, so much so that according to a 2026 review it could be among the more effective strategies now under study⁸. But alongside the results, questions have arrived about the safety of the retina, and on these the debate is still open^4,8.

In this article

1. What red light therapy for myopia is
2. Red light and myopia: the results of the studies
3. The rebound effect
4. Doubts about safety
5. Why caution is needed in Europe
6. Frequently asked questions
7. Sources

What red light therapy for myopia is

A low-power red light is used, with a wavelength of about 650 nanometres, looked at for a few minutes^2,5. How it acts is not entirely clear. The most solid evidence in humans points to a rapid thickening of the choroid, the layer rich in blood vessels behind the retina, and an increase in blood flow within it; other hypotheses, such as a role for dopamine, remain for now deductions⁸. Choroidal thickening was also measured in the 2025 meta-analysis⁴.

It should not be confused with daylight. Time spent outdoors also reduces new cases of myopia⁷, but that is another story, which we tell in the article on myopia in children.

Red light and myopia: the results of the studies

Other studies have found even more striking results. In one from 2024, on 336 children aged 6 to 12 in a single centre in China, after one year the eyes of the treated children had on average shortened by 0.11 millimetres, while in the others they had lengthened by 0.26; the photographs of the back of the eye, assessed without knowing which group they belonged to, showed no alterations of the retina². The same authors ask for the results to be confirmed in independent centres². In children with myopia of at least 4 dioptres, another study observed that after one year 53% of those treated had a shorter eye than before³.

Putting together 20 studies with 2,638 Chinese children aged 3 to 16, a 2025 meta-analysis found that, compared with control groups, red light reduced the lengthening of the eye by 0.30 millimetres at one year and by 0.61 at two, and the increase in myopia by 0.61 and 1.33 dioptres⁴. The effect was larger in more myopic children and with more frequent sessions⁴. These are large numbers, but they come from a single population and from short studies. How they compare with glasses and lenses for myopia and with low-dose atropine, also studied in Europe, we describe in the articles devoted to them.

The rebound effect

What happens at the end of treatment? In a follow-up study from 2022, children who after a year switched from red light to glasses alone had in the second year a lengthening of the eye of 0.42 millimetres, faster than that of children who had always worn ordinary glasses, 0.28⁵. Adding up the two years, their eye had nevertheless lengthened less: 0.50 millimetres against 0.64⁵. The limitation: only 57% of the children who had completed the original study were analysed⁵.

The same phenomenon emerged in a study of 108 children not yet myopic but close to being so, the so-called pre-myopia. After a year of red light, those who ended the treatment had in the second year a faster lengthening of the eye than children who had never been treated⁶.

Doubts about safety

A 2024 systematic review of 19 studies of light therapies, 13 of them on red light, found that two studies on red light reported adverse effects, and concluded that more data are needed to confirm its safety⁷. The 2025 meta-analysis, while confirming efficacy, writes that a causal relationship between the treatment and retinal damage has been hypothesised, to be investigated further⁴.

The most recent review, from 2026, takes stock. The data from clinical studies are on the whole reassuring, but there are isolated reports of retinal lesions, of transient alterations visible on OCT and of changes in the density of cones, the retinal cells used for detail and colour; and there are independent measurements of the light emitted by the devices that suggest caution⁸.

The crux is the amount of light that reaches the retina, which depends on the device. For this reason the authors call for each device to be assessed with its own parameters, instead of treating all ‘red light’ products as equal, and for treatment to be standardised and followed with retinal examinations⁸. A critical review from 2025 is more blunt: red light therapy may not be safe⁹. And the Cochrane review on myopia treatments, updated in 2025, calls for better methods to monitor and report adverse effects¹⁰.

Why caution is needed in Europe

All 20 studies in the 2025 meta-analysis involved Chinese children⁴, and the 2026 review stresses that the evidence is concentrated in a few geographical areas, that safety verification of individual devices is incomplete and that the long-term safety limits for the eye are uncertain⁸. The studies we have read do not include European children. Duration also matters: most data reach one or two years⁴, and for all myopia treatments it remains uncertain how much the effect lasts over time¹⁰.

Frequently asked questions

Is red light for myopia safe?

In clinical studies, which last one or two years, no serious harm emerged^1,2. There are, however, isolated reports of retinal lesions, and the reviews conclude that long-term safety is uncertain^4,8,9.

How much does red light slow myopia?

In a meta-analysis of 20 studies on Chinese children the eye, compared with controls, lengthened by 0.30 millimetres less at one year⁴. It is a large effect, but measured on a single population and for a few years^4,8.

Are all red-light devices the same?

No. The studies used specific devices, and the 2026 review warns that safety must be checked device by device, without generalising to all ‘red light’ products⁸.

What happens when red light treatment ends?

The eye tends to start growing faster again: this is the rebound effect^5,6. How much it matters in the long term is not yet clear¹⁰.

Red light is a promising and, at the same time, debated idea. The Chinese studies show a large effect in the short term⁴; the reviews recall that we do not yet know how long it lasts, nor how safe it is for a retina that has to last a lifetime^8,10. Until longer and independent studies arrive, in Europe too, it is a road to follow with interest and with caution.