A research team from the Hong Kong Polytechnic University has developed custom spectacle lenses that the lead investigator hopes will make myopia disappear.
Results of a two-year, randomized double-blind study enrolled 160 Chinese children were recently published. Researchers reported the spectacles slowed myopia progression by 60% in study patients. The lenses use an optical concept called defocus-incorporated multiple segments (DIMS), which has a central optical zone for correcting refractive error surrounded by areas of myopic defocus that extend to the mid-periphery of the lens.
Achieving myopic defocus is relatively straightforward when using contact lenses, a growing body of research into myopia control suggests. “However, contact lens wear may not be suitable to all” children, says Professor To Chi-ho, head of the school’s optometry department. A spectacle defocus lens may be preferred in such cases, he offers.
The key difficulty in such design is that it needs to account for eye movement, Dr. To says. “For the lens to work, myopic defocus must be experienced by the eye wherever it moves behind the lens. An evenly distributed array of microlenses or segments over the lens solved the problem and the eye will experience myopic defocus generated by these microlenses wherever it goes.” Professor To says a defocus contact lens has also been developed with positive outcomes.
“The DIMS lens for myopia control is a result of over 18 years of work of the Centre for Myopia Research of the PolyU,” he says. “From all the animal work, we know that myopic defocus (images that are formed in front of the retina) can slow down eye growth.”
Participants in the study were between the ages of eight and 13, with myopia from one to five diopters and astigmatism and anisometropia of 1.5D or less. They wore either a DIMS spectacle or a single vision lens. The mean myopic progression in the trial group was 0.21mm in the treatment group and 0.53mm in the control group, amounting to a 60% reduction in progression. Should that treatment effect remain consistent across a range of myopic corrections, it’s possible that “those who are destined to become -12D will now end up being under -5D,” Professor To speculates. “I hope DIMS lens can save a lot of people from visual impairments because of high myopia,” he adds.
|International Myopia Conference 2017 at Birmingham UK. Abstract. www.polyu.edu.hk/web/en/media/media_releases/index_id_6530.html.|