Myopia, or nearsightedness, has been on the rise globally and is becoming a major public health issue. Traditional methods of correction such as eyeglasses and contact lenses have limitations. Orthokeratology, a relatively new non-surgical technique, is proving to be an effective alternative for both slowing the progression of myopia and replacing glasses or contact lenses during waking hours. This article explores the science behind orthokeratology and its benefits compared to other myopia management options.
What is Orthokeratology?
Orthokeratology, often abbreviated as OK, is a procedure where specially designed rigid gas permeable contact lenses are used to gently reshape the cornea and temporarily reduce myopia. The contact lenses are worn overnight for 8-10 hours while sleeping and then removed in the morning. This allows unaided clear vision during daylight hours without glasses or contact lenses. The lenses gradually flatten the central cornea while steepening the periphery through controlled corneal remodeling. This change reverses itself once the lenses are removed, allowing normal unaided vision to return each morning.
How Does it Work?
Orthokeratology works by mechanically compressing the central cornea overnight using tight-fitting gas permeable contact lenses. This compresses the epithelial and Bowman's layers at the front of the cornea, thinning the central area. Meanwhile, the peripheral cornea is freed from compression and becomes relatively steeper. This has the optical effect of reducing myopia. The lenses are typically designed with different radii so that precise zones of the cornea receive different amounts of compression. Computer modeling is used to determine the right lens design for each individual's prescription.
Evidence of Effectiveness in Myopia Control
Numerous clinical studies have found orthokeratology to be effective at slowing the progression of myopia in children compared to single vision spectacles. In a 2019 meta-analysis, OK was shown to reduce myopia progression by approximately 59% over 2 years compared to single vision glasses alone. Studies have also found OK can reduce axial elongation of the eyeball, a key factor in myopia progression. The degree of slowdown depends on factors like age and initial prescription but orthokeratology remains one of the most effective non-surgical options available. For adults, OK has been shown to provide clear unaided vision during waking hours as an alternative to glasses or contact lenses.
Potential Advantages over Other Methods
Orthokeratology offers benefits over both traditional glasses and contact lenses alternatives:
- 24/7 myopia control: OK works around the clock via its corneal reshaping effect to slow progression, unlike glasses which only provide control while worn.
- No limits on outdoor time: Glasses are frequently removed for activities like sports, potentially reducing time for myopia control. OK provides persistent control.
- Improved compliance: Contact lens wear requires daily handling which some children struggle with. OK only requires lenses be worn overnight for 8 hours with morning handling.
- Clear unaided vision during day: OK allows normal unaided vision during wake hours, unlike glasses. It effectively replaces glasses for daytime wear.
- Improved self-esteem: Children prefer not having to wear glasses which can negatively impact confidence and social interaction. OK is an invisible solution in this regard.
Safety Considerations
Like any contact lens wear, orthokeratology does carry some risks that must be carefully weighed:
- Rare but serious eye infections: Poor lens hygiene practices can potentially lead to microbial keratitis, a sight-threatening infection. Risk is small (<1%) but serious.
- Discomfort from tight-fitting lenses: Approximately 5-10% of people may not tolerate the initial comfort of OK lenses and transient blurred vision upon removal is common at first.
- Dependent effect wears off immediately: Lenses must be removed and then re-worn each night for the effect to continue. Missing a night risks disruptions.
- Risks increase with improper use: As with any contact lens modality, risks are higher if lenses are not cared for, inserted, or removed properly according to professional guidelines.
Conclusion
In summary, orthokeratology is an important breakthrough for non-surgically controlling myopia progression and replacing glasses or contact lenses during waking hours. While it requires careful lens hygiene, proper fitting by an eye care professional can maximize benefits and minimize risks. As myopia rates continue rising globally, OK presents an attractive option compared to traditional correction methods alone. With further research, it holds promise as an evidence-based intervention on a public health scale.
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