Eye Freezing Used to Save Premature Babies’ Sight
An experimental treatment that freezes part of the eyes of premature babies may help save the sight of hundreds of such infants annually, a federally sponsored study said Tuesday.
The early data is so encouraging that the government decided to release the results now rather than wait for a formal announcement in medical journals later this spring, according to the National Eye Institute, which sponsored the experiments.
“This is the most significant therapy developed for retinopathy of prematurity since the disease was discovered more than four decades ago,” said one participant, Dr. Arnall Patz, professor of ophthalmology and director of the Wilmer Eye Institute at Johns Hopkins Medical Institutions.
The trials involved testing the freezing procedure in 172 very low birthweight infants who had severe cases of retinopathy of prematurity, in which developing blood vessels in the retina grow excessively, causing bleeding, scarring, detachment of the retina and blindness.
The condition is still not clearly understood, although Patz showed more than 30 years ago that it can be caused by excessive oxygen given to premature infants unable to breath on their own.
The latest study, conducted in 23 U.S. medical centers, showed that freezing spots on the surface of the white of the eye “reduced the risk of severe visual loss by one-half in 172 babies with advanced retinopathy of prematurity,” according to a Public Health Service statement.
Dr. Earl Palmer, associate professor of ophthalmology and pediatrics at Oregon Health Sciences University, who headed the study, said the cryotherapy was performed with a small hollow instrument resembling a ballpoint pen. Fifty tiny spots were frozen--to a temperature of about minus 176 degrees Fahrenheit--on the white of the eye of anesthetized infants, killing tiny portions of the developing retina underneath and blocking further abnormal blood vessel growth.
The process took from 20 minutes to two hours, Palmer said, and had no serious side effects. The average baby in the study weighed 1 pound, 12 ounces and underwent the operation about 11 weeks after birth.
Loss of Vision
According to the Public Health Service, each year more than 2,600 premature babies, weighing 3.3 pounds or less, suffer some degree of eye damage and loss of vision from retinopathy of prematurity, with about 650 babies being left legally blind from the condition yearly. Overall, the condition is responsible for 20% of blindness in children under age 5.
“This is the first proven therapy that has an impact on retinopathy that has already become established in the eye,” Palmer said.
He added that the study is continuing and researchers will be looking for clues to what could make the technique even more effective.
“The reason we are reporting results early is that analysis of incoming data indicated such a strong favorable effect that (cryotherapy) should now be considered the standard therapy. Because of the importance to infants, we felt we needed to make the information available as soon as possible,” Palmer said.
As advances in neonatal care during the 1970s and 1980s have allowed very premature infants to survive, there has been an increase in the number of infants blinded by the condition.
A first epidemic of the disorder occurred in the 1940s and 1950s, when hospitals first began using high levels of oxygen in incubators to save premature babies. Closer control of oxygen cut the incidence of the blinding condition until recently.
Control Levels
“We’ve gotten better and better at controlling oxygen levels but are finding that smaller and smaller babies are still getting the disease,” Palmer said.
The premature babies in the study had spent an average of 26.3 weeks in the womb, compared to the normal 40 weeks of gestation.
Until final details on the procedure are published in April in the Archives of Ophthalmology, the Public Health Service is urging doctors to refer premature infants with the eye problem to clinics participating in the study.
“We don’t know what will happen to these eyes that received cryotherapy in 10 to 15 years,” Palmer said.
He said it is possible the children will have reduced peripheral vision.
Because there is a 50-50 chance the condition may go away by itself and because of the uncertainty about later effects, doctors are recommending cryotherapy for one, but not necessarily both eyes of premature infants with advanced retinopathy.
