The Long-Term Effects of Orthokeratology on Myopia Progression in Children
Myopia, or nearsightedness, is a common vision condition that affects millions of children worldwide. As the prevalence of myopia continues to rise, particularly in urbanized and industrialized regions, there is growing concern about its long-term consequences. High myopia increases the risk of serious eye conditions such as glaucoma, cataracts, retinal detachment, and macular degeneration. As a result, strategies to slow down the progression of myopia in children have become a major focus in eye care.
One such strategy is orthokeratology, commonly known as Ortho-K. Orthokeratology involves the use of specially designed gas-permeable contact lenses that are worn overnight to temporarily reshape the cornea. This reshaping allows for clear vision during the day without the need for glasses or contact lenses. Beyond the convenience of daytime vision correction, orthokeratology has been shown to have a significant impact on slowing the progression of myopia in children.
How Orthokeratology Works
Orthokeratology lenses are custom-fitted to the child’s cornea and are worn only during sleep. These lenses gently flatten the cornea, which corrects the refractive error that causes myopia. Upon waking, the lenses are removed, and the child can see clearly throughout the day without the need for additional vision correction. However, the effects are temporary, and the cornea gradually returns to its original shape, necessitating nightly use of the lenses.
The primary advantage of orthokeratology lies in its dual function: providing clear vision and acting as a myopia control treatment. By altering the shape of the cornea, Ortho-K lenses create a peripheral defocus that has been shown to slow the elongation of the eyeball, which is the underlying cause of myopia progression.
Review of Long-Term Studies on Orthokeratology and Myopia Progression
Numerous studies have been conducted over the past two decades to evaluate the efficacy of orthokeratology in controlling myopia progression in children. These studies have consistently demonstrated that Ortho-K can significantly slow down myopia progression compared to traditional corrective methods such as glasses or soft contact lenses.
The Longitudinal Orthokeratology Research in Children (LORIC) Study
One of the pioneering studies in this field is the Longitudinal Orthokeratology Research in Children (LORIC) study, conducted in Hong Kong. This study followed children who were treated with orthokeratology lenses over a two-year period. The results indicated a 43% reduction in myopia progression in the Ortho-K group compared to the control group that wore regular spectacles.
The Retardation of Myopia in Orthokeratology (ROMIO) Study
The ROMIO study, also conducted in Hong Kong, further reinforced the findings of the LORIC study. In this study, 102 children were randomly assigned to either an Ortho-K treatment group or a control group wearing spectacles. After two years, the Ortho-K group showed a 63% reduction in myopia progression compared to the control group. This significant reduction in myopia progression highlighted the potential of orthokeratology as an effective treatment for pediatric myopia.
Other Notable Studies and Clinical Trials
Several other studies conducted in different parts of the world have reported similar findings. For instance, a study conducted in Spain followed 31 children using Ortho-K lenses for two years and observed a 55% reduction in myopia progression compared to children wearing glasses. Additionally, a study in Japan that followed 92 children over a five-year period found that Ortho-K lenses were effective in controlling myopia progression, with the treatment group experiencing significantly less axial elongation of the eyeball compared to the control group.
The Mechanism Behind Myopia Control with Orthokeratology
The precise mechanism by which orthokeratology slows myopia progression is not fully understood, but it is believed to be related to the way Ortho-K lenses create a peripheral myopic defocus. Traditional corrective lenses (glasses or contact lenses) focus light directly on the retina, but they may cause hyperopic defocus (where light focuses behind the retina) in the peripheral retina. This peripheral defocus is thought to stimulate the eyeball to elongate, thereby worsening myopia.
Orthokeratology lenses, on the other hand, focus light in front of the retina in the periphery, creating a myopic defocus. This defocus is believed to act as a signal to slow down the elongation of the eyeball, thus reducing myopia progression. This theory has gained support from various studies showing that the degree of peripheral defocus created by Ortho-K lenses correlates with the effectiveness of myopia control.
Long-Term Safety and Considerations
While orthokeratology has shown promise in controlling myopia progression, it is important to consider the long-term safety and potential risks associated with the treatment. The most common risks include corneal infections (microbial keratitis) and other complications related to improper lens care or poor hygiene. However, when prescribed and monitored by a qualified eye care professional, the risk of serious complications is relatively low.
Long-term studies have also looked into the sustainability of myopia control with Ortho-K. Some evidence suggests that the myopia-controlling effects of orthokeratology may continue as long as the treatment is used consistently. However, once the treatment is discontinued, myopia progression may resume, although at a potentially slower rate than if no treatment had been used.
Orthokeratology as a Myopia Management Strategy
In summary, orthokeratology has emerged as a viable option for managing myopia progression in children. Long-term studies and clinical trials have consistently shown that Ortho-K can significantly reduce the rate of myopia progression, making it an attractive option for parents and eye care professionals seeking to protect children’s vision. While the treatment is not without risks, careful monitoring and adherence to proper lens care can mitigate these concerns.
As the prevalence of myopia continues to rise globally, the role of orthokeratology in pediatric myopia management is likely to become even more significant. Parents who are concerned about their children’s myopia progression should consult with an eye care professional to determine whether orthokeratology is a suitable option for their child.