DETERMINING THE SUCCESS of a myopia control treatment is a clinical challenge. When prescribing these treatments, the short-term outcomes of patient tolerance and achieving best-corrected acuity are evident (Gifford et al, 2019). The long-term outcomes, though, involve an understanding of typical emmetropic eye growth and untreated myopia progression rates, and comparison to published research (Brennan et al, 2021).

WHEN TO MEASURE OUTCOMES

Myopia progression has been observed to be seasonal—i.e., faster in winter and slower in summer (Donovan et al, August 2012; Gwiazda et al, 2014). Hence, it is recommended to gauge outcomes of myopia control treatments after 12 months to allow for this seasonal variation (Brennan et al, 2021).

The International Myopia Institute (IMI) Clinical Management Guidelines recommend six-monthly reviews for myopic children (Gifford et al, 2019). The purposes of these different examinations can be considered as follows: the six-month review allows for assessment of the treatment suitability, ensuring appropriate visual and ocular health results along with compliance and wearing time; and the 12-month review then permits the observed annual progression to be compared to age-matched treated and untreated progression, indicating the success of myopia control (Gifford et al, 2019; Brennan et al, 2021).

EXPECTED CHANGES

Myopia progression is faster at younger ages, especially in children aged 7 to 10 years (Tricard et al, 2022). The chief determinant of expected progression—both untreated and with a treatment—is the child’s current age.

Average refractive progression for children who are “untreated” (wearing single-vision lenses) is just over –1.00D per year for 7-year-olds, decreasing to around –0.50D per year for 12-year-olds (Donovan et al, January 2012). By definition, half of each age group will progress by more than the mean, and half by less. If a child under myopia control treatment progresses by close to this “untreated” amount, this is a poor outcome. Conversely, if a child progresses minimally or by less than this “untreated” amount, this likely represents a good outcome.

Axial length growth is expected in emmetropic children until the early teenage years, growing by 0.1mm to 0.2mm until age 10, and then by around 0.1mm annually until stabilization (Mutti et al, 2007; Fledelius et al, 2014; Rozema et al, 2019; Tideman et al, 2018). By comparison, myopic children in single-vision correction progress by at least 0.3mm per year until around age 10, and by around 0.2mm per year thereafter (Rozema et al, 2019; Tideman et al, 2018; Hou et al, 2018).

Therefore, measuring annual axial length progression in a treated myope, which is close to the emmetropic expectation for their age, likely represents a strong myopia control outcome. An alternative is utilization of axial length growth charts, in which percentile outcomes can be tracked over time to gauge treatment outcomes (Klaver et al, 2020).

TREATMENT EFFICACY

There are few direct comparisons of myopia control treatments, but one wide-ranging review concluded that “No single method of treatment shows clear superiority with the best of orthokeratology, SMCLs, spectacles, and atropine showing similar effect” (Brennan et al, 2021).

As a broad category, these “best” options for myopia control treatment have been shown to slow axial elongation by at least 50% (Lam et al, 2020; Bao et al, 2022; Chamberlain et al, 2019; Cheng et al, 2022; and others. Full list available in the reference list below.). The volume of evidence for each of these treatments varies, but this concept can be applied to treatment expectations for axial and refractive changes.

Applying “average” outcomes to individual patients can be problematic, but it is evidence-based and a clinical challenge not unique to myopia management. Every patient will have individual factors influencing their outcomes. Consider these figures as “guardrails” to help support the application of research outcomes to the patient in your chair. CLS

REFERENCES

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