Early Treatment of Eye Disease in Premature Infants Decreases Risk of Lifelong Vision Problems
12/08/03 Portland, Ore.
Study has led to revised standards for identifying infants most at risk for ROP.
Among the many medical complications the girls faced was retinopathy of prematurity, or ROP, a leading cause of childhood vision loss and blindness. ROP affects premature infants who are born the earliest and with the lowest birthweights. A national study has determined premature infants at the highest risk for developing severe vision problems from ROP benefit from treatment earlier than previously thought.
The Early Treatment for Retinopathy of Prematurity (ETROP) study, published in the December issue of the Archives of Ophthalmology, found that early treatment significantly reduced the likelihood of poor vision from 19.5 percent to 14.5 percent at age one. Early treatment also reduced the likelihood of structural damage to the eye from 15.6 percent to 9.1 percent. Oregon Health & Science University's Casey Eye Institute led the Oregon trial consortium, working with hospitals throughout the state to identify premature infants with ROP.
When an infant is born prematurely, the blood vessels in the retina, the lining at the back of the eye, have not finished developing. In some premature infants, normal growth is interrupted, leading to the growth of abnormal blood vessels throughout the retina. These fragile new blood vessels can leak and bleed, causing scarring. Left untreated, a small but significant percentage of infants will develop scarring so profound the retina, which is the consistency of wet tissue paper, shrinks and pulls away from the inner surface of the eye. This can cause severe vision problems and blindness.
ROP is an unpredictable disease. In most infants, the eyes will heal in time, while in others the disease becomes severe and leads to vision loss or blindness. Physicians haven't been able to accurately predict which infants will heal and which will require treatment to prevent vision loss. Traditionally, babies have been monitored and treatment delayed until they reach the "threshold" for treatment. The threshold is the point at which a baby has a 50 percent chance of having a detached retina.
"ROP is a frustrating disease," said David Wheeler, M.D., associate professor of ophthalmology at Oregon Health & Science University's Casey Eye Institute and principal investigator for the Oregon consortium. "The results of this study give us a better understanding of which infants are most at risk for developing severe ROP and will allow us to provide timely treatment in order to spare infants a lifetime of vision problems."
As part of the study a new computerized risk model was developed to assess infants at high risk for developing severe ROP. The model identified six characteristics that put babies at higher risk, including birthweight, ethnicity, single versus multiple births, gestational age, ophthalmic exam findings and whether the baby was born in a hospital participating in the study.
Once infants had been assessed using the risk model, they were randomly assigned to one of two groups. One group received treatment at the traditional threshold; the other group received treatment at the pre-threshold level, generally seven days earlier than the traditional threshold.
ROP is treated using cryotherapy or laser therapy. Both kill the outer edges of the retina in order to stop the damaging blood vessel growth. While these treatments destroy some peripheral vision, they spare the more important central vision.
An estimated 15,000 premature infants develop ROP each year. Of these, approximately 1,500 require treatment as the disease worsens. Even with treatment, 400 to 600 babies become legally blind from the disease each year.
The ETROP study builds on the work of Earl Palmer, M.D., the director of the Elks Children's Eye Clinic at the Casey Eye Institute. Palmer directed a groundbreaking study in the 1980s that determined treatment could dramatically improve visual outcomes of infants with ROP. His work set the standard for when and how treatment for ROP should occur.
The children involved in the ETROP study will continue to be monitored through age 6 to ensure the benefits of early treatment continue into childhood. Aleeza will be one of those children. She has had three eye surgeries so far and is undergoing treatment for a weak eye. She will wear glasses for the rest of her life, but her vision was spared. Unfortunately, her sister Zoe suffered from other medical complications and died a few weeks after birth.
"ROP is just one of the many complications premature infants confront," said Val Newman, M.D., a neonatologist with Northwest Newborn Specialists who worked with premature infants enrolled in the study at Legacy Emanuel Hospital & Health Center and Providence St. Vincent Medical Center. "This study will allow us to provide better care for these tiny babies and ensure the vision of children like Aleeza is spared.
The ETROP study is sponsored by the National Eye Institute, a part of the National Institutes of Health, U.S. Department of Health and Human Services.