Young nearsighted kids benefit from bifocal contact lenses, study shows
Research identifies ‘sweet spot’ of added correction that doesn’t compromise vision
Bifocal contact lenses aren’t just for aging eyes anymore. In nearsighted kids as young as 7 years old, multifocal contact lenses with a heavy dose of added reading power can dramatically slow further progression of myopia, new research has found.
In the three-year clinical trial of almost 300 children, a bifocal contact lens prescription with the highest near-work correction slowed nearsightedness progression by 43 percent when compared to single-vision contact lenses.
Though many adults in their 40s need time to adjust to their first multifocal contact lens prescription, the kids using the same commercially available soft contact lenses in the study had no vision problems despite the strong correction. Multifocal lenses for nearsighted patients correct for clear distance vision and include an “add” of focal power for near work that challenges middle-aged eyes.
“Adults need multifocal contact lenses because they can no longer focus their eyes to read,” said Jeffrey Walline, professor of optometry at The Ohio State University and lead author of the study.
“Kids can still focus their eyes, even though they’re wearing multifocal contact lenses, so it’s like fitting them with normal contact lenses. They adapt much easier than adults.”
In nearsightedness, or myopia, the eye grows in an uncoordinated way into an elongated shape, for reasons that remain a mystery. Animal studies clued scientists in to contact lenses’ potential to keep eye growth in check by using the reading portion of multifocal contact lenses to focus some light in front of the retina – the light-sensitive layer of tissue lining the back of the eye – to slow the eye’s growth.
“These multifocal contact lenses move with the eyes and provide more focus in front of the retina than glasses do,” said Walline, also associate dean for research in Ohio State’s College of Optometry. “And we want to slow the growth of the eye because nearsightedness is caused by the eye growing too long.”
This research and other studies have led to advances in the treatment landscape for nearsighted children, Walline said. Options include multifocal contact lenses, contact lenses that reshape the cornea during sleep called orthokeratology, a specific type of eye drop called atropine, and specialty glasses.
Nearsightedness is more than an inconvenience. Myopia increases the risk for cataracts, detached retina, glaucoma and myopic maculopathy. All of these conditions can lead to loss of vision, even when wearing glasses or contact lenses. There are also quality of life factors – less severe nearsightedness improves the chances for successful laser surgery to correct vision and is not as disabling when no correction is worn, such as upon waking in the morning.
Myopia is also common, affecting about one-third of adults in the United States, and is becoming more prevalent – because, the scientific community believes, children are spending less time outdoors now than in the past. Nearsightedness tends to begin between the ages of 8 and 10 and progress up to about age 18.
Walline has been studying contact lens use in children for years and has found that in addition to the vision benefits, contact lenses also improve kids’ self-esteem.
“The youngest nearsighted kids I’ve studied with were 7,” he said. “Not all 25-year-olds can tolerate contact lens wear. About half of 7-year-olds can adapt to contact lenses reasonably, and almost all 8-year-olds can.”
In this trial, conducted at Ohio State and the University of Houston, nearsighted children age 7-11 years were randomized into one of three groups of contact-lens wearers: single vision or multifocal prescriptions with a medium reading add of 1.50 diopters or a high add of 2.50 diopters. Diopters are a unit of measurement of the optical power needed to correct vision.
As a group, the participants’ average prescription at the start of the study was -2.39 diopters. After three years, both the degree of myopia progression and the extent of eye growth were lower in the kids who had worn the high-add lenses. On average, the three-year eye growth among kids with the high-add bifocals was .23 millimeters less than in kids wearing single-vision lenses. Medium-add lenses did not slow eye growth any more than single vision lenses.
The researchers were aware of the need to balance the reduction of eye growth with any risks associated with subjecting children to strong reading power long before they need that level of correction. When testing their ability to read gray letters on a white background, there was a two-letter difference between single-vision lens wearers and those wearing multifocal lenses.
“This was about finding a sweet spot,” Walline said. “And really, what we found was that even the high-add power doesn’t reduce their vision much at all, and certainly not in a way that is clinically relevant.”
The research team is continuing to follow the same participants, treating them all with the high-add bifocal lenses for two years and then switching them all to single-vision contact lenses.
“The question is, we have slowed the growth of the eye, but what happens when we take them out of the treatment? Will they go back to where they were preprogrammed to originally? The permanence of the treatment effect is what we’ll be examining,” Walline said.
Co-authors included Donald Mutti, Lisa Jones-Jordan, Loraine Sinnott, Katherine Bickle, Alex Nixon and Gilbert Pierce from Ohio State; and Maria Walker, Amber Gaume Giannoni, Krystal Schulle and David Berntsen from the University of Houston.