Dec. 9, 2003 A new study by specialists at the Johns Hopkins Children's Center and 25 other institutions nationwide for the first time gives eye doctors a precise way to identify premature babies at the highest risk of abnormal blood vessel growth in the retina and subsequent blindness. The computerized risk assessment tool they used should lead to treatment of retinopathy of prematurity (ROP) at its earliest stages, stopping or limiting both loss of vision and structural damage to the eye.
"Before this study, we did not have a precise clinical model to follow to help predict which infants will ultimately develop vision loss from ROP, so we often had to defer treatment until the disease reached the treatment 'threshold,' at which point there was still a 25 percent chance of retinal detachment," says Michael Repka, M.D., a pediatric ophthalmologist at the Children's Center, and a member of the study team. "Unfortunately, delaying therapy to that point leaves some infants with vision loss."
Using both old and new criteria, researchers were able to identify which premature infants enrolled in the study were at highest risk for blindness. Results of their study, published in the December issue of the Archives of Ophthalmology, show 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 reduced the likelihood of structural damage to the eye from 15.6 to 9.1 percent.
According to Repka, ROP presents ophthalmologists with difficult treatment decisions because the disease can be highly unpredictable. In many infants, he says, it can spontaneously improve and spare the child's vision, while in others, it can suddenly progress and result in blindness.
For the study, the researchers identified 499 out of 828 infants diagnosed at birth with ROP as being at higher than usual risk for vision loss, based on the computerized guide that assessed birth weight, ethnicity, gestational age, direct examination of the eye, whether the infant was a single or multiple birth baby, and whether the infant had been born in a hospital that participated in the study.
Once the high risk babies were identified, 401 were randomly assigned to get either early treatment or treatment at the standard threshold. Visual activity of all infants was checked at 6 months of age, and structural outcomes were examined at 6 and 9 months of age.
Current ROP treatments - laser therapy and cryotherapy - use either heat or freezing temperatures to destroy the outer portions of the retina, slowing or reversing the abnormal growth of blood vessels A potential side effect of these treatments, known as retinal ablation, can lead to a partial loss of peripheral or side vision. However, Repka says the benefits of ROP treatments far outweighed any potential risks.
"Although there is a slight risk with ROP treatment, the benefits of these treatments are hard to ignore, since they preserve the most important part of vision - the sharp, central vision needed to read, see faces, or perform detailed tasks that require hand-eye coordination," said Repka.
Because visual activity continues to develop during infancy and early childhood, the study will continue to follow these infants until the age of 6 years to ensure that the benefits of early treatment persist into childhood.
Each year ROP affects an estimated 14,000 to 16,000 premature, low birth weight infants 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 severe ROP that requires treatment. Despite available treatment, about 400 to 600 infants with ROP still become legally blind each year. Researchers have identified birth weight of 2.75 pounds (1,250 grams) or less as a major risk factor for developing ROP.
The study was funded by the National Eye Institute, National Institutes of Health, and the U.S. Department of Health and Human Services.
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