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Researchers supported by the National Eye Institute have determined that light reduction has no effect on the development of a potentially blinding eye disorder in low birthweight infants. A paper detailing these findings is published in the May 28, 1998 issue of The New England Journal of Medicine.
The eye disease, called retinopathy of prematurity (ROP), primarily affects premature infants weighing about 2¾ pounds (1250 grams) or less and having a gestational age of less than 31 weeks. “Lighting levels in hospital nurseries have been suggested as a factor in the development of ROP, but previous research had been conflicting and inconclusive,” said Dr. Carl Kupfer, director of the National Eye Institute, one of the Federal government’s National Institutes of Health (NIH). “The results of this study help resolve this issueand allow us to explore other factors that may influence the development of this disease.”
The multicenter clinical trial was called The Effects of Light Reduction on Retinopathy of Prematurity (Light-ROP). In this study, one group of infants was exposed to normal nursery lighting conditions (the control group), and another group wore specialized goggles which dramatically reduced light exposure.
The amount of light permitted through the goggles is equivalent to wearing very dark sunglasses. Researchers found that the difference in the incidence of confirmed ROP between the two groups was not statistically significant—54 percent for the infants wearing the goggles, compared to 58 percent for the babies who did not wear goggles. “There is no significant relationship between normal nursery light and reduced light on the development of ROP in premature babies,” said James Reynolds, MD, Chief of Pediatric Ophthalmology at The Children’s Hospital of Buffalo and chairman of the Light-ROP study. “It is unlikely that reducing nursery lighting by having infants wear the type of goggles used in this study would affect their risk of ROP.”
Dr. Reynolds said that researchers also found “no significant effect of reduced light in the nursery and the severity of ROP,” although he said data on this topic was limited.
ROP is caused when abnormal blood vessels grow and spread throughout the retina, the nerve tissue that lines the back of the eye. The scarring and bleeding caused by the excess growth of these blood vessels can lead to retinal scarring or detachment from the back of the eye, resulting in vision loss. There are approximately 3.9 million infants born in the U.S. each year; of those, about 28,000 weigh 2¾ pounds or less. About 14,000-16,000 of these infants are affected byROP. In most cases, the disease regresses and leaves no permanent damage. However, about 1,100-1,500 infants annually develop ROP that is severe enough to require medical treatment.
The most effective proven treatment for ROP is cryotherapy, in whichphysicians briefly touch spots on the surface of the eye with acryoprobe, an instrument that generates freezing temperatures. Thefreezing temperature reaches the retina to stop the growth of abnormalblood vessels. The effectiveness of cryotherapy was demonstratedseveral years ago through another NEI-sponsored clinical trial.However, even with cryotherapy, about 400-600 infants with ROP becomelegally blind each year. More recently, laser therapy also has beenutilized in addition to cryotherapy. Unfortunately, a sizeableminority of patients still have vision loss.
Lighting in hospital nurseries is generally similar to typicaloffice fluorescent lighting. Although there is no specific lightingstandard, routine lighting in nurseries can vary considerably withinand between nurseries. Some nurseries periodically keep the lightingat a lower level, especially at night. Researchers used specializedgoggles for the study because simply turning down the lights in thenursery is not a reliable method of light reduction for an individual infant. Also, babies in nurseries can be exposed to a variety of light sources, such as sunlight or reflected light from another baby undergoing light therapy for jaundice. The Light-ROP study carefully monitored the actual light levels in nurseries. None of the infants involved in the study were exposed to any increase or reduction in nursery lighting beyond that found in a standard hospital nursery. Apart from the goggles, infants in both groups received the same medical care.
A list of study centers follows.
Study Centers for the Light-ROP Clinical Trial
James D. Reynolds, MD
Kathleen Kennedy, MD
W.A.J. Van Heuven, MD
Robert J. Hardy, Ph.D.
The Effects of Light Reduction on Retinopathy ofPrematurity Study
The Effects of Light Reduction on Retinopathy of Prematurity (Light-ROP) study was a clinical trial designed to test the hypothesis that reducing light exposure would reduce the incidence of retinopathy of prematurity (ROP) in low birthweight infants. This multicenter clinical trial was supported by the National Eye Institute (NEI), one ofthe Federal government’s National Institutes of Health.
The cause of ROP is not known, and several complex factors may be responsible for its development. In the 1950s, researchers supported by the National Institutes of Health determined that the relatively high levels of oxygen routinely given to premature infants at that time werean important risk factor; reducing the level of oxygen given topremature babies reduced the incidence of ROP. Today, ROP has reemergedas an important public health problem. Advances in neonatal care meansmaller and more premature infants are being saved. These infants are ata much higher risk for ROP.
The Light-ROP study enrolled its first patient in July 1995 and completed patient enrollment in March 1997. Informed consent was obtained from the parents, and 409 infants initially became participants in the study. Of these, 205 were placed in goggles within the first 24hours of birth, and 204 received the usual care in the nursery without goggles (the control group). Only those infants from both groups who survived and could participate in the study (188 infants in the gogglegroup and 173 in the control group) are included in the study’s results.
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- Reynolds JD, Hardy RJ, Kennedy KA, Spencer R, van Heuven WA, Fielder AR. Lack of Efficacy of Light Reduction in Preventing Retinopathy of Prematurity. Light Reduction in Retinopathy of Prematurity (LIGHT-ROP) Cooperative Group. N Engl J Med. 1998 May 28. PubMed