Infant Study Says Swiftness Saves Sight
Many low birth-weight infants can be saved from blindness caused by a form of retinopathy if pediatricians start treating them aggressively early in the course of their disease, according to a major new government study.
Because the course of the disease can be highly variable, doctors have previously delayed treatment until significant progression has been observed. But a study of 317 newborns at 26 U.S. medical centers showed that early treatment can reduce the likelihood of poor vision by a quarter and the risk of serious eye damage by a third.
The findings are important because pediatricians are saving the lives of ever-smaller infants, in effect trading a certain death for a risk of blindness and other long-term disabilities.
The findings, reported in the December Archives of Ophthalmology, “will have a major impact on clinical practice,” wrote Dr. Alistair R. Fielder of Imperial College London in an editorial in the same journal.
The finding is but the latest in a series of retinopathy treatment discoveries that have been “nothing short of revolutionary,” he added.
The disease, known as retinopathy of prematurity, is a risk in as many as 16,000 premature infants in the United States each year and much larger numbers abroad. It is caused by the abnormal proliferation of blood vessels in the eye, leading to leakage, scarring and retinal detachment.
Treatment involves cauterizing the blood vessels with a laser or freezing them, but that entails a risk of loss of peripheral vision, so pediatricians have been cautious in attacking the problem too early.
The disorder became the leading cause of blindness in children in the United States in the 1940s when physicians began placing premature infants in incubators containing high levels of oxygen. A landmark 1954 study sponsored by the National Institutes of Health demonstrated that excess oxygen greatly increased the risk of blindness. The practice was immediately halted.
More recently, government-sponsored studies have shown that normal light levels in nurseries do not increase the risk of blindness and that small doses of supplemental oxygen can be safely administered. But the incidence of blindness has been increasing again as advances in neonatal care have enabled the survival of smaller newborns.
Some infants who appear to be in the early stages of retinopathy recover spontaneously, while others proceed to marked vision loss. Until recently, it was extremely difficult to tell which group was which, and physicians postponed treatment until infants had a 50% likelihood of their retinas becoming detached.
Treatment could rescue many such children, but nearly 20% developed very poor vision and 15% had structural deformities of the eye.
During the late 1990s, researchers led by biomathematician Robert J. Hardy of the University of Texas School of Public Health developed a formula to predict which infants were at highest risk.
Using the formula, a team led by Dr. William Good of the Smith-Kettlewell Eye Research Institute in San Francisco identified 317 infants at high risk. Half were given immediate treatment to block the blood vessel proliferation, while half were not treated until the risk of retinal detachment reached 50%.
The team reported that 14.5% of those given early treatment were likely to develop poor vision, compared to 19.5% of those given conventional treatment. Similarly, 9.1% of those given early treatment had structural damage to the eye, compared with 15.6% of those treated conventionally.
The screening method developed by Hardy incorporates digital imaging of the retina, and such imaging will become increasingly important in “countries where ophthalmic expertise is particularly sparse,” Fielder said. In the near future, it may be possible to identify risk automatically based on one or a few images, a development that would allow screening by technicians rather than physicians.
Treatment could then be supervised via the Internet by ophthalmologists in other countries.
