Under-correcting myopia may increase the risk of myopia progression in children. Discover the history of under-correction for myopia control and what medical experts recommend today.
When I was a child, I was diagnosed with myopia and was recommended to get a pair of glasses. However, when I went to the optician for the glasses, they lowered my prescription, believing it would slow the progression of my myopia.
But now I have learned that under-correction is not an effective strategy and may even have accelerated my myopia, leaving me wondering how much of my high myopia was due to under-correction throughout the years.
Myopia is a vision condition that distant objects appear blurry and may lead to vision-threatening complications, especially high myopia. This condition affects millions of people globally, with approximately 23% of the population suffering from myopia. Shockingly, this number is projected to increase to 50% by 2050. In the United States, around one-third of the population has myopia, and this number is predicted to rise to nearly 60% by 2050.
Myopia control is important to stop or slow down myopia progression, and various treatment strategies, such as more outdoor time, antimuscarinic eye drops, and myopia control glasses and contact lenses, are now confirmed to be effective as research advances. However, some initial treatment strategies that were once thought to be promising were found not beneficial or sometimes even potentially harmful.
One of the initial treatment strategies for myopia control was under-correction, which some practitioners advocated and practiced while more research was underway to confirm its effectiveness. However, as more evidence emerged, under-correction was found to have no significant impact on myopia progression or even may potentially increase its risk.
This post will delve into research studies on under-correction in myopia and the recommendations from medical authorities to provide you with a better understanding of the best practices for managing your children's myopia.
The start of under-correction practice in myopia control
The strategy of under-correction for myopia control was initially discussed in the literature back in the 1850s. The under-correction theory suggests that by wearing glasses or contact lenses that don't fully correct your vision, your eyes wouldn’t need to work as hard to focus on things that are close. This reduces demand on your eye muscles and can help slow down the progression of myopia.
Animal studies found that when animals were exposed to blurred vision, similar to under-correction, their myopia progression slowed down. This led to the idea that prescribing under-corrected glasses for myopia could bring the focus point in front of the retina and help slow the progression of myopia.
A small Japanese study in 1965 supported under-correction as a strategy for myopia control in children. The study found that full correction of myopia with full-time wear resulted in myopia progression of -0.75D, whereas under-correction resulted in -0.54D, a difference of -0.21 D between full correction and under-correction.
As a result, some healthcare providers and physicians around the world began advocating and practicing under-correction as one of the early treatment strategies for myopia control, while more research was underway to confirm the discovery.
However, not all eye care professionals supported the idea of under-correction and subsequently criticized the study's limitations, such as a small sample size, problematic statistical analysis, and possible interference to the finding due to the concurrent use of other pharmacological interventions for myopia control.
Recently, there has been a renewed interest in utilizing under-correction as a strategy for myopia control, which may be due to a 2017 study involving 12-year-old Chinese children. This study found that children with no correction had slower myopia progression of -0.15 D per year when compared to children with full correction. The author suggested that myopic defocus, or the blurry vision from under-correction, might act as an inhibitor of eye growth in humans. However, the author also noted that there were limitations to the study, such as differences in the baseline characteristics of the children prone to progression and potential selection bias due to the study design.
Despite these findings, there were doubts in the medical community about the hypothesized effects of under-correction. They argued if under-correcting myopia can slow down or halt the progression of eye growth, then uncorrected mild myopia should be a self-limiting condition that either resolves on its own or should have stopped myopia from ever developing. Furthermore, several robust studies published shortly after also suggested the opposite.
Evidence against under-correction
Today, top myopia authorities, such as the panel experts representing the European Society of Ophthalmology, the International Myopia Institute, and the American Academy of Ophthalmology, all recommended full correction of myopia to reduce the likelihood of progression after reviewing available research studies. In fact, they have called out that research indicated that under-correction is not beneficial and can even be harmful. [Jacobs 2022; Németh 2021]
Let's take a closer look at studies that these myopia experts reviewed. One 2012 study compared the rate of myopia progression in young people who did not wear glasses (uncorrected) to those who wore fully corrected glasses. The study found that the uncorrected participants had faster myopia progression, at a rate of 0.45D, over a one-year follow-up period than those who were fully corrected.
Furthermore, three well-designed studies examined the effects of different levels of under-correction. In a trial from 2006, researchers found that under-correction of -0.5 D in children produced a slight increase in myopic progression over an 18-month period compared to full correction, but the increase was not statistically significant.
Another study by Chung and colleagues involved children aged 9-14 years old with myopia over a two-year period. The study found that an under-correction of -0.75D resulted in more rapid myopia progression, with a difference of 0.23D between the under-corrected and fully corrected groups.
In a third study that looked at a lower level of under-correction (-0.25 to 0.5D), children wearing under-corrected glasses had slightly but statistically significant greater myopic progression than those who were fully corrected at the end of the 12-month study.
Lastly, in a study conducted in the US, researchers found a positive correlation between the under-correction of refractive error and myopia progression, with greater amounts of under-correction associated with greater myopia progression.
It is also important to note that recent systematic reviews indicated that there was no strong evidence of benefits, but were potential risks for myopia progression when considering all available studies. These meta-analysis studies showed that full correction of myopia had a lower likelihood of myopia progression compared to a -0.5 to -0.75 D under-correction, with a mean difference of -0.11D to -0.15D per year. [Walline 2020; Huang 2016]
Key takeaways
While under-correction for myopia control might have seemed to be a promising strategy, it was later demonstrated not effective in slowing the progression of myopia -- and might even increase the likelihood. After reviewing all available evidence available, medical authorities across the world concluded myopia should be treated with full correction.
As the prevalence of myopia continues to increase, it is essential for parents to stay informed about the latest research on myopia control strategies and work with eye care professionals to ensure children receive appropriate treatment.
By staying informed and taking proactive steps, you can help protect your children's vision for a lifetime.
Learn more about the basics of myopia.
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