July 28, 2004.
By: Drs. Mary Elizabeth Hartnett and David Wallace,
UNC Health Care.
Retinopathy of prematurity, or ROP, is the most common cause of blindness in premature infants today.
Although most infants with ROP do not become entirely blind, many are at risk for poor vision development -- that is not always helped with glasses -- unless they have continued eye care throughout childhood. Fortunately, with improvements in screening, technology, and awareness, vision problems from ROP have been reduced.
In the 1950s and 60s, exposure to high levels of unregulated oxygen was recognized as an important cause of ROP, which at the time was called retrolental fibroplasia or RLF. As a result, today neonatal intensive care units throughout the United States employ sophisticated equipment to monitor the infant’s oxygen level and prevent exposure to dangerously high oxygen.
Today, ROP likely occurs because of several complicated and interrelated factors, such as low birthweight, overall health, and fluctuations in oxygen. Infants born with birthweights less than 2.75 pounds (1250 grams) or less than 31 weeks gestation (a full term is about 40 weeks) are at risk of ROP.
Each year in the United States about 28,000 infants are born weighing 2.75 pounds or less. Of these, 14,000-16,000 develop ROP and 1,100-1,500 infants progress to a level of severity requiring treatment. About 400-600 infants are legally blind from ROP each year in the United States.
ROP affects the retina, which is a neural tissue lining the inner part of the back eye wall that communicates with the brain and is essential for vision to occur. The retina is not visible without special optical lenses. In normal development, retinal blood vessels grow within the retina to supply oxygen and nutrients necessary for continued development.
Complete development requires that retinal blood vessels cover and supply the entire extent of the retina. This process is often not finished until full term. In the premature infant, development of the retina is incomplete at birth leaving portions of the retina without blood supply and, therefore, without nourishment or oxygen.
The retina without normal retinal vascular nutrition creates a vulnerable environment and causes misdirected, uncontrolled growth of incompetent blood vessels that create scarring and retinal detachment. It is the retinal detachment that most often leads to blindness.
ROP management begins in the neonatal intensive care unit. Infants at risk are screened on a regular basis by an ophthalmologist (a physician or M.D. who specializes in eye disease). If ROP is detected, examinations are continued until ROP resolves, which occurs in 9 out of 10 infants, or until ROP becomes severe enough to warrant treatment.
Today, ROP in infants is typically treated with laser surgery, or less commonly, cryotherapy (freezing), to the retina void of normal blood vessel growth. The laser treatment causes the misdirected blood vessels to resolve more than half of the time.
Recently, a clinical trial called the Early Treatment for Retinopathy of Prematurity (ETROP) study was performed in several centers throughout the country that analyzed clinical criteria that predict which infants will ultimately develop severe misdirected blood vessel growth in ROP. From the ETROP study, new guidelines were developed as to when to treat an infant at moderately high risk without unnecessarily treating an infant at low risk. In general, earlier treatment is better.
Even with early laser treatment, about 10 percent of infants with severe ROP can develop retinal detachment. Recently, a study published in the April 24 issue of the journal Retina analyzed retinal features in eyes treated with laser for ROP to determine those eyes at the greatest risk of developing progressive retinal detachment.
This study helped to define the window of time when vitreoretinal microsurgery is needed to treat an early retinal detachment that would progress to cause blindness without subjecting an infant eye at low risk of progressive retinal detachment and blindness to unnecessary surgery. This vitreoretinal surgery requires retinal expertise and is performed by retina-fellowship trained ophthalmologists who usually have further specialization in surgery of the pediatric retina.
In infants who develop ROP and are discharged from the neonatal intensive care unit with ROP, it is very important for parents to keep follow-up appointments with the ophthalmologist to monitor the ROP until it resolves or requires treatment, whether by laser or vitreoretinal microsurgery.
Once ROP resolves, the infants should continue to have ophthalmology examinations to maximize their visual development throughout their childhood. In teenage years, examinations of the retina are also important because there can be an increased risk of late-onset retinal detachment.
Parents who would like to have their child evaluated for ROP treatment at UNC may request an appointment by calling (919) 966-2061.
• Mary Elizabeth Hartnett, MD, is a retinal ophthalmologist at the University of North Carolina at Chapel Hill with further specialty training in pediatric retina surgery. She was the lead author of the study on features predictive of progressive retinal detachment cited above.
• David Wallace, MD, is a pediatric ophthalmologist at the University of North Carolina at Chapel Hill and an investigator in the ongoing ETROP study.
• Early Treatment For Retinopathy Of Prematurity Cooperative Group. Revised indications for the treatment of retinopathy of prematurity: results of the early treatment for retinopathy of prematurity randomized trial. Arch Ophthalmol. 2003 Dec;121(12):1684-94.
• Hartnett ME, McColm JR. Retinal features predictive of progressive stage 4 retinopathy of prematurity. Retina. 2004 Apr;24(2):237-41. Copyright ©2004 TWEAN Newschannel of Raleigh, L.L.C. dba News 14 Carolina.
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