Published in Research

Do seasonal variations impact myopia treatment efficacy?

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4 min read

A new study in Eye & Contact Lens investigated whether there were variations by season in orthokeratology’s (ortho-k) effect on myopia progression.

Give me some background first.

Myopia progression in children is understood to be multifactorial, with influences such as education and natural light exposure or time spent outdoors, contributing to its development.

Further: Previous studies have shown that myopia progression is slower during the summer (due to longer days before sunset) versus in the winter (with earlier sunsets, equating to shorter days).

As such: Researchers hypothesized that this correlation is related to more time outdoors and fewer hours in school during the summer.

Now, talk about the study.

This retrospective study focused on individuals who had been treated with ortho-k lenses for 1 year.

Individuals were separated into four groups by season and instructed to wear ortho-k lenses for at least 8 hours each night.

  • Patients’ axial length (AL) was measured at baseline as well as at 3-month intervals; changes in AL were measured and compared between groups.

Before we get into the data, talk specifics on these patients.

A total of 116 children aged 7-12 years were included in the study—all diagnosed with myopia. They also were required to have:

  • A baseline spherical equivalent refractive error (SER) between -3.50 and -0.75 D
  • An astigmatism of 1.50 D or less
  • No other ocular or systemic diseases
  • No history of treatment with low-concentration atropine was included in the study.

Now to the findings.

After 1 year of continuously wearing ortho-k lenses, the mean AL among each group showed seasonal variation had a significant effect on myopia control.

The mean axial elongation over 1 year for each group was (P<0.001):

  • Group 1 (spring): 0.33±0.08 mm
  • Group 2 (summer): 0.30±0.10 mm
  • Group 3 (autumn): 0.21±0.08 mm
  • Group 4 (winter): 0.22±0.09 mm

In addition, axial elongation was significantly higher in winter months than in summer months (0.09±0.06 mm vs. 0.05±0.05 mm, P<0.001).

What did investigators conclude?

Based on this data, researchers deduced that there was better myopia control effect with ortho-k lenses when treatment was initiated in the autumn and winter months than in the spring and summer months.

Further, patients’ axial elongation during the summer months was 56% of that during the winter.

  • Most significantly: They determined that, for children with a rapid progression of myopia, initiating treatment with ortho-k lenses in autumn or winter may have a more significant effect on controlling myopia.

Limitations?

The study authors noted the following limitations:

  • As this was a study involving all Chinese myopic children, results may differ within different ethnic groups and geographical regions
  • The nature of a retrospective study, rather than a randomized controlled trial with large sample size, allowed for the possibility of confounding factors
  • Changes in age and treatment efficacy were not followed continually

And lastly: the take home.

These findings support that seasonal variation affects myopia progression with ortho-k lens treatment.

Further: The data also highlights that seasonal variation should be controlled for as a variable in future studies investigating myopia interventions.


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