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Sunday, July 23, 2017

Academics & Research

College of Optometry researchers fight myopia, blindness


Myopia exists when light focuses in front of the retina, rather than on top of it. | Courtesy of David Gee/College of Optometry

The University of Houston’s College of Optometry is leading the charge in the fight against myopia, or nearsightedness, with several studies aimed at discovering how to fully stop the progression of the condition in children — a problem that can lead to permanent blindness.

Dr. Earl Smith, Dean of the UH College of Optometry, was named one of the “Most Influential in Optometry” in 2015 for his extensive research into myopia and was recently awarded a $1.9 million research grant by the National Eye Institute to help fund his ongoing work. Dr. David Berntsen is part of a clinical trial for children’s contact lenses that builds off of some of Smith’s work, and Dr. Ruth Manny worked on two studies that tested eyeglasses and looked for myopia risk factors.

“We’re in the middle of an epidemic of myopia,” Smith said. “In Asia, East Asia, for example: Japan, Hong Kong, Taiwan, Singapore — if you look at the kids graduating from technical high schools in urban areas, 80 to 95 percent are nearsighted, and they’re not a little bit nearsighted. They’re a lot nearsighted.”

Myopia exists when the eye grows too long on its axial length, Smith said, so light from a faraway object focuses in front of the retina, rather than on it. This causes objects at large distances to look blurry.

The myopia epidemic, Smith said, is likely caused by intense educational practices and lack of time outside for children. Sitting indoors, reading and studying for long hours does not give the eye enough variety in distance or exposure to sunlight. Everything inside is close to the eye, Smith said, while everything outside is far away, giving the eye the needed signal to slow growth.

Myopia is one of the largest causes of permanent blindness in Asia, he said, and the condition is taking hold in the United States. From 1970 to 2000, the number of myopia sufferers in the adult population jumped from to 45 percent from 25 percent. Those with severe myopia increased by a factor of eight, Smith said.

An estimated five billion people — half of the earth’s population — will be nearsighted by 2050 if nothing is done about the epidemic, Smith said. One billion of those five billion people will have severe myopia, Smith said, which is likely to lead to permanent blindness.

Glasses and contact lenses are the most common ways to correct nearsightedness, Smith said, because they change the focus of the light received by the eye so that it comes to rest on the retina. 

Smith said the goal of his research is to understand the role of vision in affecting eye growth. The eye has corrective systems in place so that during development, if vision is blurry, the eye will grow to correct it.

At first, Smith said, his research was focused on those suffering from lazy or crossed eyes. His focus shifted once he found that visual experience plays a key role in the development of those conditions and myopia.

“Vision regulates the way the eye grows, whether one is nearsighted or not,” Smith said. “It’s a fascinating thing. The eye uses visual feedback associated with defocus to regulate the way the eye grows. Because of changes in our behavior, those systems sometimes operate in ways that cause the eye to become nearsighted.”

Smith said the biggest contribution his research made was proving that the periphery vision could dominate eye growth. If corrective bifocal contact lenses are applied, giving the wearer clear vision while simultaneously correcting the peripheral vision, eye growth will be slowed and myopia can be avoided, Smith said.

Dr. David Berntsen, an associate professor at the College of Optometry and fellow recipient of funding from the National Institutes of Health, is working on the Bifocal Lenses In Nearsighted Kids clinical trial.

“My funding and the primary work in my lab is clinical trials in kids, looking at specific types of lenses to see if they can slow myopia progression,” Berntsen said.

The funding Berntsen received is a different type of grant system that funds large-scale clinical trials, he said. The BLINK study is a collaboration between UH researchers and colleagues at Ohio State University.

BLINK enrolled about 150 kids at UH and 144 at Ohio State University, aged 7 to 11-years-old, over the course of about a year and a half, Berntsen said.

Berntsen explained that each child is randomly assigned one of three kinds of contact lenses. The control lens is one that is normally prescribed to correct myopia. The other two are bifocals with varying degrees of plus-power in the periphery of the lens focusing the light sooner at the edges, controlling eye growth according to the findings of Smith’s research. The peripheral light is then focused in front of the retina, which sends a signal to the eye to slow growth.

Traditional lenses give the wearer clear central vision, but peripheral light focuses behind the retina, which may stimulate the eye to grow longer, which exacerbates myopia, Berntsen.

Corrective lenses are the standard of care for treating myopia, Berntsen said, so there are no studies comparing myopic progression with lenses versus no lenses. There are studies that have found that peripheral light focused behind the retina — like with traditional spectacles — is associated with faster progression than when peripheral light is focused in front of the retina, like with Berntsen’s bifocal contacts.

Berntsen said the ultimate goal of his research is to stop eye growth in myopic children, but currently it can only be slowed.

Another College of Optometry professor, Dr. Ruth Manny, was involved in a similar study in 2008. The Correction of Myopia Evaluation Trial aimed to understand differences in the progression of myopia in children wearing different types of eyeglasses.

“The question COMET was designed to answer was: Is the increase in nearsightedness that occurs as children get older different between children who wear eyeglasses with progressive additional bifocals (no line bifocal) and children who wear conventional single vision spectacle lenses?” Manny said in an email.

There were 469 children enrolled in four different cities: Houston, Boston, Philadelphia and Birmingham, Alabama. Manny said that after three years of study, researchers found that while myopia progression was less in those children wearing bifocals, the difference was too small to recommend no-line bifocals as a method to treat myopic children.

The results of COMET have led researchers to explore different treatments, Manny said, such as the bifocal contact lenses in Berntsen’s study.

Manny was also involved in a study called the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error that looked at 13 risk factors for myopia in children, and found that refractive error, or light focusing incorrectly within the eye, was the single best predictor of the condition.

Despite working within the same college at UH, Smith, Berntsen and Manny are not directly involved in each other’s research, they explained.

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