A new trial has shown that multifocal contact lenses reduce worsening nearsightedness in children. These findings are published in the Journal of the American Medical Association, today.
The study, funded by the National Eye Institute, a part of the National Institutes of Health, found that children wearing multifocal contact lenses had slower progression of their myopia.
The Bifocal Lenses in Nearsighted Kids (BLINK) Study shows that there is an option of controlling development of nearsightedness, in children now. This is good news as this condition increases the risk of cataracts, glaucoma and retinal detachment later in life, is left untreated.
Myopia is a condition which occurs if a child’s developing eyes grow too long from front to back. In this condition, instead of focusing images on the retina (the light-sensitive tissue in the back of the eye), images of distant objects are focused at a point in front of the retina. This result in children having a good near vison but a poor long-distance vison.
Traditionally, this condition is corrected by single vision prescription glasses and contact lenses. But that does not solve the underlying issue of myopic vision.
But now studies have shown that multifocal contact lenses can correct myopic vision in children while simultaneously slowing myopia progression by slowing eye growth. Typically, multifocal lenses are used to improve near vision of people over the age of 40 years.
The U.S. Food and Drug Administration approved one lens for myopia control in November 2019. So, primarily, the use of multifocal contact lenses to slow myopia progression has been off label since many years.
How It Works
Multifocal contact lenses are shaped like a bullseye. The two different portions of the lens help focus the light.
The center portion of the lens corrects nearsightedness so that distance vision is clear, and it focuses light directly on the retina. The outer portion of the lens adds focusing power to bring the peripheral light rays into focus in front of the retina. The higher the power of the outer portion, the further in front of the retina it focuses peripheral light.
Previous animal studies have indicated that if light is focused in front of the retina, it can slow the eye growth. However, with single vision glasses and standard contact lenses peripheral light is focused to a point behind the retina, which prompts the eye to keep growing.
The New Study
In this new study, researchers examined if multifocal contact lenses really slowed progression of myopia and if high-add power contact lenses provided better slowing of myopia progression and eye growth than medium-add power contact lenses.
The study included 287 myopic children between the ages of 7 to 11 years old. When the study started, the children required -0.75 to -5.00 diopters of correction to achieve clear distance vision.
The subjects were than randomly provided single vision contact lenses or multifocal lenses, the outer lens of which were either high-add power (+2.50 diopters) or medium-add power (+1.50 diopters). They wore the lenses during the day as often as they could comfortably do so.
After a period of three years, the scientists observed that the children in the high-add multifocal contact lens group had the slowest progression of their myopia.
The multifocal lenses also slowed eye growth. The three-year adjusted eye growth was .42 mm for the high add group, .58 mm for the medium add group, and .66 mm for the single vision group.
David A. Berntsen, O.D., Ph.D., associate professor and Golden-Golden professor of optometry at the University of Houston, and the chief scientist on the study said, “Our study shows that eye care practitioners should fit children with high-add power multifocal contact lenses in order to maximize myopia control and the slowing of eye growth”.
He also added that compared with single vision contact lenses, multifocal lenses slow myopia progression by about 43% over three years.
This is good news as myopia rates have increased over the past five decades. In 1971, 25% of Americans were myopic, compared to 33% in 2004. By 2050, the worldwide prevalence of myopia is projected to be 54%, and the prevalence of high myopia, the most severe form, is projected to increase to 10%.
Reasons for this increase is unclear, but experts attribute it to increasing screen times, decreasing outdoor time, and genetic factors.