The bright lights of intensive care nurseries may contribute to more than 500 premature infants becoming blind each year, according to researchers at two Washington hospitals whose findings were published today in the New England Journal of Medicine.
The researchers found that premature infants were exposed to lights up to four times as bright as office lighting for stays ranging up to 100 days. Lights in intensive care nurseries have increased fivefold to tenfold in the last two decades and often are on round the clock, they found.
The findings may explain why the problem of infant blindness has again reached the epidemic levels experienced during the 1950s. During that decade, premature infants routinely received oxygen to help their underdeveloped lungs before researchers realized that excessive oxygen damages the development of blood vessels in the eye.
The study examined 333 premature infants who were treated at Georgetown University and Children's hospitals in 1981-82.
The authors found there were more cases of eye problems among infants exposed to the usual nursery illumination than those whose incubators were shielded with transparent acetate filters.
The smallest babies were at greatest risk of developing eye problems, technically referred to as retinopathy. Infants affected by the condition can develop normal vision, or they can develop near-sightedness, crossed eyes, lazy eyes, or in extreme cases, blindness.
Two of the infants, both under 2.2 pounds at birth, became blind. The study's primary author, Penny Glass, a development psychologist who performed the study for a doctorate at George Washington University, is seeking a grant to further study the other infants' vision and ability to process visual information.
Lights in nurseries have become increasingly bright to enable medical personnel to monitor the sophisticated life-saving equipment. Little attention has been paid, however, to possible harmful effects of the brighter lights, according to Glass. Animal research has found that light may make eyes more susceptible to the damaging effects of oxygen, she said.
Normal office lighting is about 40 foot-candles, a scientific measure of light. By comparison, light in the nurseries studied ranged from 35 to 190 foot-candles, and was highest for babies placed near windows.
Light has long been used to correct the problem of infant jaundice, but babies receiving those light treatments routinely have their eyes covered.
An editorial in the New England Journal advises hospitals to modify newborn nurseries by lowering the lights or installing equipment that automatically cycles lights off and on.
The need to illuminate infants for medical reasons, such as checking the color of the skin or performing a test, is sporadic and can best be handled by turning on a spotlight, "thereby sparing neighboring infants unnecessary exposure to high light levels," the editorial said. "It is not necessary, however, to light up an entire nursery to see one infant in such detail."
The doctors noted in the study, however, that continuous dim light may not be best for a premature infant and suggested studies be done on how infants respond to light cycled on and off during their nursery stay.
"The study already has had an effect," said Glass, who noted that both local nurseries studied reduced their lighting to an average of 25 foot-candles in 1983.
"I think architects will start adding more light switches so everything doesn't have to be illuminated. People have been saying for years that exposure to bright, continuous light may not be good for preemies and now we've shown it scientifically."