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Commonly Held Beliefs About Myopia That Lack A Robust Evidence Base



The above controversial paper basically reported what a lot of practitioners had been educated on myopia control. What is going on? The following is a very brief summary of this paper.


List of Myths that was challenged :


- 0.01% Atropine

It cited a paper by Yam JC et al., 2018 'Low-concentration atropine for myopia progression (lamp)study: A randomized, double-blinded, placebo-controlled trial of 0.05%, 0.025% and 0.01% atropine eye drops in myopia control.' Which had 100 subject in each arm for 12 months, compared to placebo, 0.01% had 12% of control which was not statistically significant.


- Relative peripheral hyperopia leads to myopia development & progression

Atchinson et al. reported that though measurement of relative peripheral hyperopia were consistent in most studies between hyperope, emmetrope and myope, the effect did not predict myopia onset and progression reliably. Though interventions imparting peripheral addition like orthokeratology and multifocal soft contact lenses works, it's contribution due to peripheral hyperopia is limited due to the optic that passes through the pupil and the proportion of ray that reaches the central versus peripheral retina.


- Undercorrection

Several studies had shown binocular undercorrection to have worse or no difference in myopia progression. Those that showed otherwise had study design flaws that biased the result. However, there were monocular undercorrection studies that slowed myopia progression. It needs to be switched daily between eye and is no practical. With insufficient studies to prove efficacy, undercorrection is usually not done as it affects learning outcome.


- Treatment effect throughout the treatment period

From the figures below, there is reduced efficacy in most treatment mode. This however, did not look at the rebound effect should the treatment mode is stopped except for atropine.

- Treatment effect is not the same for all progression range

Treatment effect in studies is a group average, not individual effect and may not apply in real life due to different rate of progressors. Some are faster than others and will affect the treatment effect. In addition, ethnicity is also a major factor that affects efficacy of treatment.


- Hand-held digital devices contribute to myopia

Myopia had been an issue in Asia since the 1980's and the first commercial smartphone was only launched in 2007. There were theories about accommodation, peripheral hyperopic defocus and lesser time spent outdoor due to handheld devices. There were no studies that found direct cause and effect of handheld devices on myopia.


- More time outdoors slows myopia progression

Influence of time spent outdoors has been shown to delay myopia onset. However, the effect on myopia progression has limited effect with dramatic change in lifestyle to have large amount of time outdoor (9 hours per week) in order to have any myopia control of about 29.1% for refraction and 25% for axial elongation.


- Impact of outdoor activity is due to daylight

Though outdoor activity has an effect on myopia onset, the effect is multi-factorial and not solely due to light level and spectral intensity as shown in several animal studies. Studies shown that defocus was a strong predictor to regulate eye growth compared to light. The effect of light on myopia could be due to constriction of pupils which improves the depth of focus, reduces hyperopic defocus, influencing the refractive state.


- Subclassification for myopia

High myopia used to be classified as pathological myopia. Pathological myopia was later changed to myopia with pathological findings above a certain threshold. Though the risk for disease complications is exponentially correlates with refractive error, it is present for ALL myopes.


- Myopia is a condition with negative dioptric number

Criteria for the presence of myopia in most studies were set at -0.25D and worse. However, studies that look at annual change found that myopic shifts occurs before diagnosis. From the knowledge of normal progression of refraction with Zadnik et al, the lack of low amount of hyperopia in children is a good prediction for myopia onset and progression.


- Conclusion

This review was not meant to stop practitioners from advocating myopia control but it is meant as an education for practitioners and parents that myopia is multifactorial and suggestions are based on credible science. Products or methods with promising results need to have more than 1 year of results on both refractive and biometry measures.


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