New Eye Implant Clears Cloudy Vision
A new type of cornea implant could restore some vision in infants and children who are blind due to a cloudy or damaged cornea, a study has found.
The cornea is a typically clear covering of the eye that serves as our window to the world. But in some children, conditions like glaucoma, infections and vitamin A deficiency can cloud the cornea as if an opaque curtain has been pulled over that window.
Corneal blindness is the world’s fourth leading cause of blindness, following cataract, glaucoma and age-related macular degeneration, according to the World Health Organization.
While natural corneas from donors are the main source for transplants, such tissue can trigger rejection by the immune system as well as scarring from infections or out-of-control blood vessel growth. In the United States, approximately 20 percent of corneal transplant patients—between 6,000 and 8,000 a year—reject their donor corneas, according to the National Eye Institute.
The contact-lens-sized implant is made of plastic and is sewn into the patient's eyeball with a piece of donor tissue. Physicians at the University of Rochester Eye Institute and Johns Hopkins University performed the implant operations on 17 children, aged six weeks to 13 years old. Together, the children had racked up 39 traditional failed cornea transplants.
Two of the children received another type of artificial implant that failed, while 15 received the “K-Pro” device. All 15 of those children recovered some vision, sometimes remarkably so, and none had an infection. In the seven cases where the child was at least 4 years old and could describe results, each could at least see fingers held at arm's length.
""Thirty years ago, our hope was that after the operation, patients could see well enough to see some movement and care for themselves for a few years. That was considered success,” said James Aquavella of the University of Rochester, who operated on the children. “Now many of our patients are out driving cars, riding horses, and leading active lives, and several have near-normal vision soon after the operation."
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Corneal transplants have been trickiest in children, whose immune systems are relatively vigorous and can mount more powerful attacks against foreign tissue than adults. For the best results, children must receive the implant before their vision is permanently shot, doctors say.
"If the brain has been deprived of vision at an early age, it's permanently affected, no matter how well the eye is focused later on. That's why it's crucial to intervene early on,” said one of the doctors involved in the operations, Matthew Gearinger of the Eye Institute.
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Jeanna Bryner is managing editor of Scientific American. Previously she was editor in chief of Live Science and, prior to that, an editor at Scholastic's Science World magazine. Bryner has an English degree from Salisbury University, a master's degree in biogeochemistry and environmental sciences from the University of Maryland and a graduate science journalism degree from New York University. She has worked as a biologist in Florida, where she monitored wetlands and did field surveys for endangered species, including the gorgeous Florida Scrub Jay. She also received an ocean sciences journalism fellowship from the Woods Hole Oceanographic Institution. She is a firm believer that science is for everyone and that just about everything can be viewed through the lens of science.