Published: Dec. 8, 2003
Updated: Nov. 3, 2004
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By Duke Medicine News and Communications
DURHAM, N.C. -- In a new study, eye researchers at locations throughout the U.S., including Duke University Eye Center, have demonstrated that premature infants at highest risk for severe vision loss caused by retinopathy of prematurity (ROP) retain better vision when treatment is administered at an earlier stage of severe disease rather than at the previously accepted threshold for treatment. By using an improved risk assessment tool to more accurately identify which premature infants were most likely to develop severe vision loss from the disease, researchers were able to target treatment for babies who needed it and avoid treating those whose cases may resolve on their own.
ROP is a potentially blinding eye disease that affects premature, low birth weight infants. The disease is among the most common causes of vision loss in childhood and can lead to lifelong vision impairment and blindness. ROP spurs the growth of abnormal blood vessels, which leak fluid and blood in the back of the eye leading to retinal scarring and increasing the risk of retinal detachment. Retinal detachment is the main cause of visual impairment and blindness in ROP.
"For years, many of us who screen and treat premature infants with ROP have suspected that earlier laser treatment for the more aggressive cases of the disease might improve the visual outcomes of some of these very tiny infants," said Sharon Freedman, M.D., a pediatric ophthalmologist at the Duke Eye Center and lead investigator at this site. "These study results suggest that we can feel more comfortable that we're providing timely treatment in high risk cases and feel justified in watchful waiting of those babies with ROP who are not at high risk for severe visual loss."
The findings of the Early Treatment for Retinopathy of Prematurity (ETROP) study appear in the December 2003 issue of the Archives of Ophthalmology.
Treatments for ROP include laser therapy, which uses heat from light energy, or cryotherapy, which uses freezing temperatures, to retard the growth of blood vessels in the eye. One consequence of these treatments, called blood vessel ablation, is a partial loss of peripheral or side vision. However, treatment is valuable to preserve the most important part of the visual field -- the sharp, central vision needed to read, see faces or perform detailed tasks that require hand-eye coordination, the researchers said.
A total of 401 infants were enrolled at 26 study locations throughout the U.S. Once identified, the infants were assigned randomly either to treatment at the standard threshold or to early treatment. The standard treatment threshold for ROP depends on the disease having progressed enough that the risk of retinal detachment approaches 50 percent.
Researchers found that early treatment significantly reduced the likelihood of poor vision from 19.5 percent to 14.5 percent at about 1 year of age. Early treatment also considerably reduced the likelihood of structural damage to the eye from 15.6 percent to 9.1 percent.
As part of the ETROP study, the researchers used a new computerized risk model to identify high-risk infants at earlier stages of the disease. The risk model assessed birth weight, 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.
Because the course of ROP is often unpredictable, treatment decisions can be difficult for physicians to make, said Freedman. In many cases ROP regresses spontaneously, sparing an infant's vision. In other cases, however, ROP progresses and results 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 that can accurately predict which patients will ultimately develop severe vision loss from ROP, ophthalmologists have been forced to defer treatment until treatment was clearly indicated. Delaying therapy, however, can leave infants who might benefit from early treatment with poor visual outcomes, said Freedman.
ROP affects approximately 14,000 to 16,000 infants annually in the United States and thousands more worldwide, making it a leading cause of vision loss in children. Of these cases, approximately 1,500 infants will develop ROP severe enough to require treatment. Despite available treatments, about 400 to 600 infants with ROP still become legally blind each year. Infants with birth weights of 2.75 pounds (1,250 grams) or less are at major risk for developing ROP, the researchers say.
The ETROP study will continue to follow these infants until age 6 to ensure that the benefits of early treatment persist into childhood, said Freedman. "By following the babies who received treatment through the study until they reach 6 years of age, we'll be better able to judge the longer term beneficial effect of the treatment. Alternatively, we'll also be able to see if there have been any detrimental effects," she added.
The study was funded by the National Eye Institute (NEI) of the National Institutes of Health. The 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.