12 Aug. 2020. Results of a clinical trial show contact lenses that focus light on multiple areas of the retina reduce near-sightedness in children. Results of the Bifocal Lenses In Nearsighted Kids, or BLINK, study appear in yesterday’s issue of the Journal of the American Medical Association (paid subscription required).
Near-sightedness, or myopia, occurs when eyes in children grow too long from front to back, which forces eyes to focus in front of the retina, the light-sensitive area located at the back the eye. As a result for people with myopia, objects in the distance are seen as blurry, while objects up close are seen clearly. And if left untreated, myopia can increase the risk of glaucoma, cataracts, or detached retinas later on.
Single-vision glasses and contact lenses can correct the distant-vision problem, but do not address the underlying issues. These corrective lenses focus distant objects directly on the retina, but peripheral light then focuses behind the retina, which keeps extending the eye. National Eye Institute, part of National Institutes of Health and a co-sponsor of the study, says myopia has increased in the U.S. from a quarter of the population (25%) in 1971 to one-third (33%) in 2004.
Multi-focal contact lenses offer an alternative. The center portion of these soft lenses focuses light directly on the retina, like single-vision lenses, but outer areas of the lenses capture and focus peripheral light in front of the retina, to reduce the retina’s extension from myopia. Multi-focal lenses are prescribed for people over age 40 to correct near vision, and the BLINK study tested their effectiveness as a tool for slowing the progression of myopia in children.
The clinical trial enrolled 294 participants, children age 7 to 11, at optometry schools at Ohio State University in Columbus and University of Houston. The children, all with myopia, were randomly assigned to receive multi-focal contact lenses with high or medium power, or single-vision contact lenses for comparison. The high-power lenses have 2.5 diopters, a unit of refractive correction, while the medium-power lenses have 1.5 diopters. The monthly disposable lenses are commercially available and provided by CooperVision in Victor, New York.
The study team monitored participants for three years, tracking changes in their myopia and length of the eyes over that time. The results show the multi-focal lenses slow myopia progression compared to single-vision lenses. Corrections needed for myopia among children receiving higher-powered lenses increased by 0.60 diopters, compared to 0.89 diopters for medium-power lens recipients, and 1.05 diopters for single-vision lenses. Results also show evidence of higher-power lens recipients experiencing less eye growth than medium-power and single-vision lens recipients.
“It is especially good news to know that children as young as 7 achieved optimal visual acuity and got used to wearing multi-focal lenses much the way they would a single vision contact lens,” says Jeffrey Walline, professor of optometry at Ohio State and chair of the BLINK Study Group in a National Eye Institute statement. “It’s not a problem to fit younger kids in contact lenses. It’s a safe practice.”
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