New research shows that specially designed eye retainers can slow down the increase in poor eyesight for kids. New technology called Orthokeratology is kind of like braces for your eyes.
Slowing down progressively worsening eyesight in Children using Orthokeratology
Myopia (nearsightedness) is a serious public health issue that affects millions of people worldwide.
East Asia is a region that is particularly vulnerable to the crisis, with more than sixty percent youngsters affected.
In most instances, myopia starts affecting people at a young age and may progress to high myopia over a period of time.
In the long run, high myopia often leads to other complications such as glaucoma, cataract, and myopic fundus disease.
Experts suggest that eye elongation is the primary factor that causes myopia in young children.
This means that myopia can be controlled by slowing down the axial length’s elongation.
Researchers and clinicians around the world have spent decades to come up with the ideal therapeutic pathway to prevent or reduce myopic progression.
Introduced for the first time in the 1960s, Orthokeratology (also referred to as Ortho K or OK) is a clinical technique to reduce myopia progression by temporarily reshaping the cornea surface.
Rigid contact lenses with reverse geometry design are used in this technique for reshaping and hence modifying the refractive power of the corneal profile during overnight lens wear.
In this methodology, the central corneal epithelium gets thinned and the corneal profile is reshaped.
Initially, some concerns were raised concerning this technique’s safety in terms of microbial keratitis (MK). However, in the recent years, these apprehensions have been addressed satisfactorily.
As a result, use of Orthokeratology for myopia control has become more common in recent years.
Recent clinical trials have established that overnight OK can help reduce axial eye elongation by approximately 45% in progressive myopic children. However, in terms of efficacy, there can be significant individual variability.
Specially designed rigid contact lenses commonly known as reverse geometry lenses are used in Orthokeratology. The lenses are required to be worn overnight only, and should be removed in the morning on awakening.
While wearing the OK lens overnight, the cornea gets flattened and the eye care practitioner fine tunes the same to correct the myopic refractive error of the patient.
It is important to remember that while the lens is not being worn, the cornea tends to gradually regain its original shape. Therefore, only temporary refractive correction is provided by this technique.
Right now, many different OK lens designs are available on the market and all of them are broadly based on the principle of reverse geometry design.
This design fundamentally comprises of three distinct zones. Compared to the central corneal curvature, the lens’ base curve or central zone is fitted flatter.
This zone’s function is to reduce the power of the central cornea by its flattening, leading to myopia correction. A reverse curve zone surrounds the central curve zone, and comprises of one or more curves that are steeper compared to base curve.
Sigmoid, aspheric, or spherical curves are used in this zone, helping maintain lens centration and supplement the forces that are responsible for flattening the central cornea.
Finally, there is a zone of alignment in the periphery of the reverse curve zone. This zone aids in lens centration and bears the weight of the lens. Aspheric or tangent peripheral curves are most commonly used for the alignment zone. In order to facilitate tear circulation, this zone is surrounded by an edge lift.
A unique and unusual geometric pattern is demonstrated on the eye by reverse geometry lenses, which reveals the lenses’ characteristic back surface design features.
After wearing these lenses overnight, there is a corneal topographic change with a central corneal flattening zone. By analyzing these changes, practitioners can make the necessary lens parameter refinements to ensure perfect fit for the lens and optimize the refractive changes caused by corneal reshaping.
It has been observed that myopia is reduced by the highest extent of approximately 75% correction takes place after the very first night of using OK. In general, about 7 to 10 nights of overnight OK is said to be sufficient for achieving full correction of myopia.
However, slight regression of this effect is observed during the day when the patient no longer uses the lens. This regression is most pronounced immediately after commencing OK treatment and tends to lessen over a period of time. In most instances, this is not more than 0.25–0.50 D, and is clinically managed by targeting a slight over-correction. Correction of up to 4.00 D of myopia can be successfully targeted wearing OK lens.
In the recent years, several clinical studies have been conducted to gain insights into the efficacy of Orthokeratology in myopia correction.
In 2015, the Australia based School of Optometry and Vision Science’s Research in OK Group published the findings of a randomized contralateral eye clinical trial where a comparison was carried out between the myopia control effects of conventional daily wear lens and OK lens.
