Contact lenses are widely used as an alternative to glasses to correct the wearers’ refractive error like myopia, hyperopia, astigmatism, and presbyopia. The use of contact lenses has few advantages over spectacle, whereby it allows the wearer to remain glasses free for sport, provide wider field of view, and minimize the magnifying/minifying effects of ophthalmic lenses. Additionally they often improve the cosmetic appearance of the wearer leading to higher self-confidence.
The usage of contact lenses had caught the eye of many researchers, when few studies has claimed that contact lens could be used effectively to slow down the progression of myopia. For example, one of the studies in 1990 found that rigid gas permeable lenses wearer had lower myopia progressions than the control group (spectacle wearer)1. Since then, contact lenses have been used by many eye care practitioners as myopia control treatment.
Currently, there are two types of specialty contact lenses commonly used for myopia control in the market, orthokeratology and multifocal soft contact lenses. These contact lenses were designed specifically to reduce the peripheral hyperopic defocus effects which are responsible for longer eyeballs in myopic eye2.
Orthokeratology or Ortho-K is one of the first contact lenses used for myopia control. It involves fitting a pair of rigid gas permeable (RGP) lenses on the wearer’s cornea with the assistance of a computerized corneal topography that helps to map the corneal surface curvature. The Ortho-K lenses work in 2 ways. Firstly, the Ortho-K lenses flatten the central region of the cornea to correct the refractive error and to restore the clear vision. While the peripheral area of the Ortho-K lenses steepening the mid-peripheral area of the cornea to control the progression of myopia.
The wearer is required to wear the Ortho-K lenses overnight (more than 8 hours) for the treatment. Then the wearer will have clear vision on the next day without the need of any spectacle or contact lenses. The study showed that the usage of Ortho-K lenses helps to slow down the myopia progression up to 45%3. However, patients may experience initial discomfort with the RGP lenses due to the rigidity of the RGP lenses. Besides that, wearer compliance and regular follow up visits are important to ensure its success and to avoid other possible adverse effects such as corneal infection or ulcer.
Until recently, the use of multifocal soft contact lenses or myopia control soft contact lenses had been gaining popularity. The disposable soft contact lenses are made from softer materials such as hydrogel or silicone to reduce the initial discomfort. The soft myopia control contact lenses consist of few circular zones, where the central circle zone (correction zone) helps to correct the wearer’s distance refractive error, whereas the peripheral treatment zone creates peripheral myopic defocus which reduces the stimulus for eyeball axial length elongation. This will effectively slow down the myopia progression in children.
Study by Bifocal Lenses in Near-sighted Kid (BLINK) randomized clinical trial revealed that the centre distance multifocal soft contact lenses or Myopia control contact lenses are also effective in the myopia control4. Besides, the same study had found that the prescriptions of higher addition multifocal lenses had yielded better effects.
In summary, the usage of contact lenses as the new way of myopia control treatments is a growing trend in Malaysia, especially among schoolchildren. It can be used in conjunction with other available treatments such as low dose atropine eye drops and myopia control spectacle for better effects.