Outdoor Time and Myopia Progression: The Seasonal Signal

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September 14, 2026

By John Nguyen, BOptom

When a parent asks what else they can do about their child’s myopia, most of us say the same thing: get the child outside. For a child not yet myopic, it is prevention, and we mean it. Once that child is myopic, it often becomes a closing remark, offered after the lens or the drop has been prescribed. The words do not change. The weight behind them does.

Both positions are defensible. Outdoor time was never going to hold an established myope on its own, and none of us would ask it to. But somewhere in that shift, not sufficient by itself becomes not effective. Those are different claims. That outdoor time cannot adequately control a progressing myope is a question of clinical adequacy. That it has no effect on an already-myopic eye is a biological claim, and that has never been established either way.

What if it stays unsettled because the first claim keeps answering for the second?

The starting point: seasonal variation

Multiple studies show that myopia progresses unevenly throughout the year. Donovan reported six-month progression of 0.31D in summer against 0.53D in winter in Chinese children.¹ COMET showed it in American children,² and Hecova in European ones.³

The cause is less clear. Light exposure is the leading environmental mechanism proposed, with retinal dopamine signalling among the pathways implicated.⁴ But summer also brings school holidays, so near work falls at precisely the moment daylight rises, and none of these studies cleanly separated the two. Season is not a clean proxy for daylight.

So what is new?

Three retrospective Chinese studies have asked whether it persists in children already being treated.

• Ding and colleagues followed 600 children in orthokeratology. Six-month axial elongation was 0.12 ± 0.09 mm in winter against 0.07 ± 0.09 mm in summer.⁵
• Tang and colleagues, at Peking University People’s Hospital, reported seasonal variation in a smaller orthokeratology group of 116 children.⁶
• Li and colleagues compared children in DIMS spectacles with 0.01% atropine against children in OrthoK. The seasonal split appeared in both, but was less pronounced under the combination and no longer significant at older ages.⁷ The authors thought the smaller seasonal effect might be connected to the use of atropine.

All three are retrospective, from northern China, and two share investigators. None measured light exposure directly, or could separate daylight from the other behavioral changes of the seasons. What they establish is narrower. In treated children the seasonal pattern persists, and it appears under more than one modality.

Why it stays unsettled

Two methodological problems keep this question open. The first is how the exposure has been measured. Ho noted that 12 of 13 included studies relied on questionnaires.⁸ Hours outdoors counts a child under a covered walkway in late afternoon the same as that child at midday. Those two are nowhere near each other in illumination. If the measure cannot tell them apart, it could easily miss a real effect. Wu, in 2018, used light meters and found intensity mattered alongside duration.⁹ He monitored both in 6,295 Shanghai schoolchildren, where the protective effect related to each.¹⁰ But that trial was built around onset.

The second is that the trials were built to answer the onset question. Xiong, in 2017, found outdoor exposure protective against onset, but could not demonstrate a dose-response relationship for progression.¹¹ A 2024 meta-analysis reached much the same conclusion, while finding a benefit of 0.05 mm in non-myopic children.¹² Whether that reflects a smaller effect in established myopia, poor exposure measurement, or too little sensitivity to detect a modest one, remains unresolved.

The findings that argue the other way belong here as well. Wu, in 2013, ran the recess trial often cited for progression, but the apparent progression benefit was largely driven by children not myopic at baseline.¹³ Dhakal, reviewing seven systematic reviews, found the reductions in already-myopic eyes small enough to question their clinical meaning.¹⁴ Nor is the literature consistent. The same 2019 analysis reported a bigger reduction in axial elongation in already-myopic children than in non-myopic ones.⁸

Where this leaves us

We cannot yet say that greater outdoor light exposure slows progression once an eye is myopic, and neither can we say that it does not. The recent findings do lean one way, though. The seasonal effect has been reported across different populations and settings, is observed during active treatment and now appears under two modalities. Most intervention studies have measured outdoor time rather than light dose and have been designed around onset rather than progression. The seasonal signal is reproducible. What has not been established is whether light causes it.

Outdoor time belongs in the myopia management plan as an adjunct. That rests on the onset evidence and a mechanism with no reason to stop at diagnosis—not on a demonstrated progression effect. It is a rough measure of the exposure that may matter, but it is the handle we have. But an adjunct is judged by what it adds rather than by whether it could replace anything, and this one is low cost and carries broader health benefits with appropriate sun protection.⁴

So what does that mean in the room? Timing. That progression runs faster in winter is not novel. That it persists in a child already in OrthoK or on atropine is newer. Li points toward additional control measures through those months, without going as far as stating which ones specifically.⁷ Outdoor time has a habit of surfacing when progression does, offered as a reason rather than a recommendation. This message is most important as we head into the months with the least daylight, when myopia management plans are under the greatest pressure.

And we should treat it as a real adjunct, one that deserves to be discussed, documented and revisited. An adjunct is more than an optional extra, and the recent evidence makes it harder to treat it as one.

 

 

John Nguyen, BOptom, is an Australian optometrist and the founder of Luxi Health, which develops daylight-tracking technology for children. He writes and speaks internationally on myopia. The author declares a commercial interest in Luxi Health.

 

References

1. Donovan L, Sankaridurg P, Ho A, et al. Myopia progression in Chinese children is slower in summer than in winter. Optom Vis Sci. 2012;89(8):1196-1202. doi:10.1097/OPX.0b013e3182640996
2. Gwiazda J, Deng L, Manny R, Norton TT; COMET Study Group. Seasonal variations in the progression of myopia in children enrolled in the Correction of Myopia Evaluation Trial. Invest Ophthalmol Vis Sci. 2014;55(2):752-758. doi:10.1167/iovs.13-13029
3. Hecova L, Rusnak S, Salcman V, Cendelin J. Seasonal variations in ocular axial length increase among children in the Czech Republic. J Ophthalmol. 2023;2023:2592853. doi:10.1155/2023/2592853
4. Lingham G, Mackey DA, Lucas R, Yazar S. How does spending time outdoors protect against myopia? A review. Br J Ophthalmol. 2020;104(5):593-599. doi:10.1136/bjophthalmol-2019-314675
5. Ding W, Zhao C, Li X, et al. Seasonal variation in axial elongation in children with orthokeratology treatment. Ophthalmic Physiol Opt. 2025;45(3):877-882. doi:10.1111/opo.13486
6. Tang T, Li Y, Zhao M, Wang K. Seasonal variation in the effect of controlling myopia progression using orthokeratology. Eye Contact Lens. 2025;51(9):394-399. doi:10.1097/ICL.0000000000001205
7. Li X, Zhao C, Yin M, et al. Comparison of seasonal variation in myopia progression: defocus incorporated multiple segment spectacle lenses in combination with 0.01% atropine vs orthokeratology. Clin Ophthalmol. 2026;20:582774. doi:10.2147/OPTH.S582774
8. Ho CL, Wu WF, Liou YM. Dose-response relationship of outdoor exposure and myopia indicators: a systematic review and meta-analysis of various research methods. Int J Environ Res Public Health. 2019;16(14):2595. doi:10.3390/ijerph16142595
9. Wu PC, Chen CT, Lin KK, et al. Myopia prevention and outdoor light intensity in a school-based cluster randomized trial. Ophthalmology. 2018;125(8):1239-1250. doi:10.1016/j.ophtha.2017.12.011
10. He X, Sankaridurg P, Wang J, et al. Time outdoors in reducing myopia: a school-based cluster randomized trial with objective monitoring of outdoor time and light intensity. Ophthalmology. 2022;129(11):1245-1254. doi:10.1016/j.ophtha.2022.06.024
11. Xiong S, Sankaridurg P, Naduvilath T, et al. Time spent in outdoor activities in relation to myopia prevention and control: a meta-analysis and systematic review. Acta Ophthalmol. 2017;95(6):551-566. doi:10.1111/aos.13403
12. Li D, Min S, Li X. Is spending more time outdoors able to prevent and control myopia in children and adolescents? A meta-analysis. Ophthalmic Res. 2024;67(1):393-404. doi:10.1159/000539229
13. Wu PC, Tsai CL, Wu HL, Yang YH, Kuo HK. Outdoor activity during class recess reduces myopia onset and progression in school children. Ophthalmology. 2013;120(5):1080-1085. doi:10.1016/j.ophtha.2012.11.009
14. Dhakal R, Shah R, Huntjens B, Verkicharla PK, Lawrenson JG. Time spent outdoors as an intervention for myopia prevention and control in children: an overview of systematic reviews. Ophthalmic Physiol Opt. 2022;42(3):545-558. doi:10.1111/opo.12945

 

 

Read more about how environment and lifestyle impact myopia here