Seasonal Changes May Affect Myopia Treatment Outcomes Somewhat

Research published in Eye & Contact Lens revealed seasonal variations in orthokeratology treatment effectiveness in Chinese children with myopia. Results showed that axial elongation was less in summer than in winter and that starting ortho-K in autumn/winter yielded better control. This highlights the interplay of environmental factors like daylight exposure and outdoor activity with ortho-K's mechanisms, suggesting seasonal timing could optimize myopia management. Click image to enlarge. It’s well understood that both genetic and environmental factors play a role in myopia progression. Studies continue to look more closely at environmental influences on children, and have identified intensive education, lack of natural daylight exposure and insufficient outdoor activity time as contributors to the condition. Seasonal variations have also been shown to be associated with myopia progression, suggesting axial elongation slows down in the summer months compared to winter, likely because of the amount of time children spend outside. However, a group of researchers from China wondered whether seasonal variations would matter if children were also undergoing orthokeratology (ortho-K) treatment to slow progression. Their results, recently published in Eye & Contact Lens, support earlier findings that the time of year does influence axial elongation.The retrospective study included 116 Chinese children with myopia (62 boys and 54 girls; ages seven to 12) who completed one year of ortho-K treatment . Based on initial time wearing ortho-K, subjects were classified as four groups: spring group (March-May), summer group (June-August), autumn group (September-November) and winter group (December-February). Axial length (AL) was measured every three months for one year. Axial elongation over time and between groups was compared. The mean axial elongation over one year wearing ortho-K varied from 0.22mm to 0.33mm depending on when the regimen was initiated; better results were seen for those beginning in autumn or winter. Also, statistically significantly higher mean axial elongation was observed in winter months than that in summer (0.09mm vs. 0.05mm), the researchers reported in their paper.“The persistence of seasonal variation in treated eyes implies that environmental factors, such as daylight exposure and outdoor activity, may interact with ortho-K’s biomechanical and optical mechanisms,” the authors wrote. “Ortho-K lenses likely reduce baseline elongation rates through peripheral myopic defocus and corneal reshaping, but seasonal environmental drivers (such as dopamine signaling from light exposure) may still exert residual influence. Notably, the absolute elongation in our ortho-K group (0.21-0.33mm/year) was markedly lower than untreated cohorts (0.30-0.48mm/year), documenting ortho-K’s overall efficacy despite seasonal fluctuations. Moreover, the axial length of first-time ortho-K lens wearers increased an average of about 0.1mm less in autumn/winter compared with spring/summer; while modest for an individual patient, this could accumulate over multiple years.“For children with rapid progression, initiating ortho-K in autumn/winter might amplify control efficacy,” they continued. “Besides, the superior control effect in summer months reflects both intrinsic seasonal ocular growth patterns and an enhanced therapeutic response under summer conditions.”The authors also offered the reasons why seasons may have exerted an influence on ortho-K treatment in these children. “Compared with winter months, summer has greater light intensity and longer illumination time,” they wrote. “Summer school vacation in Beijing typically lasts two months during July and August and one month of winter vacation from mid-January to mid-February. With more daylight  during summer months, children will have more time to engage in outdoor activities which also reduces time spent on close work indoors. “Outdoor light intensity is markedly greater than that indoors, and their eyeballs will be exposed to more light, increasing levels of light-induced retinal dopamine,” they wrote. “Meanwhile, being outdoors can relax the ciliary muscle and alleviate accommodative spasm.”Some limitations mentioned by the researchers included the fact that this was not a prospective randomized controlled trial, and that its design as a retrospective study could introduce confounding factors. Longitudinal changes in age or treatment efficacy decay were not tracked dynamically, they added, and the study population specific to Chinese children may mean children from other regions and ethnicities will have different outcomes.The authors propose that future research should account for seasonal factors in myopia control studies and investigate their impact on other treatment approaches like atropine and defocus spectacles. “Although small in magnitude, this seasonal effect emphasizes the importance of standardizing seasonal timing in research and suggests a low-cost optimization strategy for clinical practice,” they concluded.Click here for the journal source. Tang T, Li Y, Zhao M, Wang K. Seasonal variation in the effect of controlling myopia progression using orthokeratology. Eye & Contact Lens. June 27, 2025. [Epub ahead of print.]