December 9, 2003.
Doctor's Guide Publishing Limited.
BETHESDA, MD --
An important clinical trial, sponsored by the National Eye Institute (NEI), a part of the National Institutes of Health (NIH), has provided doctors with improved prognostic indicators and treatment options for retinopathy of prematurity (ROP), a blinding disease that affects premature, low birthweight infants. ROP spurs the growth of abnormal blood vessels in the back of the eye. These vessels leak fluid and blood and scar the nerve tissue inside the eye, increasing the risk of retinal detachment and severe vision loss in infants.
Because it follows an unpredictable course, ROP presents doctors with difficult treatment decisions. In many infants the disease spontaneously regresses and spares vision. However, in some infants ROP progresses, resulting in serious visual impairment. Although current therapy can stem its progression, many infants are still blinded by the disease. Due to a lack of clinical criteria to predict which patients will ultimately develop severe vision loss from ROP, ophthalmologists were forced previously to defer treatment until it was clearly indicated. Unfortunately, as it turns out, delaying therapy can leave infants who might benefit more from early treatment with poor visual outcomes.
The Early Treatment for Retinopathy of Prematurity (ETROP) study results, published in the December issue of the Archives of Ophthalmology, demonstrated that premature infants, who are at the highest risk for developing vision loss from ROP, will retain better vision when therapy is administered in the early stage of the disease. This treatment approach was found to be better than waiting until ROP has reached the traditional treatment threshold. Just as importantly, the study also established the value of an improved risk assessment model to more accurately identify those infants who are at the highest risk for developing severe vision loss from ROP.
"Premature, low birthweight infants face a host of medical complications with lifelong consequences. The results of this study allow us to improve treatment for ROP and, hopefully, the quality of life for children who most need sight-saving therapy," said Paul A. Sieving, M.D., Ph.D., director of the NEI.
"This is a great step forward in research to treat blinding eye diseases," said NIH Director Elias Zerhouni, M.D. "The NIH will continue to look for new ways to treat and even prevent ROP, which is one of the leading causes of severe vision loss in infants and young children."
Each year ROP affects an estimated 14,000-16,000 premature, low birthweight infants in the United States and thousands more worldwide, making it a leading cause of vision loss in children. Of these cases, approximately 1500 infants will develop severe ROP that requires treatment. Despite available treatment, about 400-600 infants with ROP still become legally blind each year. Researchers have identified birthweight of 2.75 pounds (1250 grams) or less as a major risk factor for developing ROP.
The previous standard treatment threshold for ROP hinged on the disease having progressed enough that the risk of retinal detachment approached 50 percent. As part of the ETROP study, a new computerized risk model, developed by NEI-supported researchers, was used to identify high-risk infants early in the disease. The risk model assessed birthweight, ethnicity, being a single or multiple birth baby, gestational age, ophthalmic exam findings, and whether the infant had been born in a hospital that participated in the study. "This new risk assessment model proved invaluable in the early detection of infants who have a high risk of blindness and may require treatment. It also allowed us to better identify and monitor those patients who are less likely to require treatment," said Robert J. Hardy, Ph.D., the University of Texas School of Public Health at Houston researcher who led the efforts to develop this improved risk model.
Once identified, the infants were then assigned randomly either to treatment at the standard threshold (50 percent chance of retinal detachment) or to early treatment. Researchers found that early treatment significantly reduced the likelihood of poor vision from 19.5 to 14.5 percent at about one year of age. Early treatment also considerably reduced the likelihood of structural damage to the eye from 15.6 to 9.1 percent.
Current treatments for ROP involve laser therapy or cryotherapy. Laser therapy uses heat from light energy while cryotherapy uses freezing temperatures to retard blood vessel growth. A consequence of these treatments, known clinically as blood vessel ablation, is a partial loss of peripheral or side vision. Nonetheless, treatment is valuable in preserving the most important part of our sight -- the sharp, central vision we need to read, see faces or perform detailed tasks that require hand-eye coordination.
"It is crucial that infants with high-risk ROP be identified early and be given timely treatment," said the chair of the study William Good, M.D., of the Smith- Kettlewell Eye Research Institute in San Francisco. "Early treatment could save infants from a lifetime of visual impairment. The results also clearly indicate that for certain subgroups of eyes, watchful waiting and not immediate treatment is the best approach."
The study will continue to follow these infants until age six to ensure that the benefits of early treatment persist into childhood. "Because visual acuity continues to develop during infancy and early childhood, the long-term effect of early treatment on visual development is not yet fully known. We expect that the significant benefits to vision found in this study will persist into childhood, but we have to be sure," Dr. Good said.
The study was conducted at 26 participating centers in the U.S. A list of study centers is attached.
The National Eye Institute (NEI) conducts and supports research that leads to sight-saving treatments and plays a key role in reducing visual impairment and blindness. The NEI is part of the National Institutes of Health (NIH), an agency of the U.S. Department of Health and Human Services.
SOURCE: National Eye Institute
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