Retinopathy of prematurity (ROP) was first diagnosed in 1942 and remains a leading cause of childhood blindness worldwide. ROP is caused by abnormal development in the retinal blood vessels of premature infants, primarily those who weigh 1,250 grams (2¾ pounds) or less at birth and are born before 31 weeks gestation. The blood vessels of the retina begin to develop about 3 months into pregnancy and complete development at the time of normal birth. The smaller the baby is at birth, the higher the risk of developing ROP.
Not all babies who are premature develop ROP, and about 90 percent of all infants with ROP have a mild form of the condition, which usually improves and leaves no permanent damage. Infants with more severe disease can develop impaired vision or even blindness.
There are five stages of ROP. Many children who develop stages 1 and 2, with mild to moderate abnormal blood vessel growth, improve with no treatment and eventually develop normal vision. Stage 3 ROP is characterized by severely abnormal blood vessel growth, and infants with stage 4 disease have a partially detached retina. Infants with stage 5, the end stage of the disease, have a completely detached retina. Untreated, stages 3-5 ROP can result in severe visual impairment and even blindness.
Ophthalmologists skilled in the evaluation of infant eyes make the diagnosis of ROP after dilation with drops and examination. All babies born before 31 weeks gestation and weighing less than 3 pounds at birth are screened for ROP. Other risk factors for ROP include heart disease, breathing difficulties, high levels of carbon dioxide (CO2) in the blood, low blood oxygen, respiratory distress, poor weight gain, anemia and blood transfusions.
In 2003, laser therapy for early stage 3+ ROP became the standard of care based on the results of the ETROP (Early Treatment for ROP) clinical trial.
From March 2007 to October 2010, 150 infants were enrolled in the BEAT-ROP clinical trial (Bevacizumab Eliminates the Angiogenic Threat for ROP) to study the use of an intravitreal anti-VEGF (anti-vascular endothelial growth factor) injection versus laser therapy for both early and advanced stage 3+ ROP. McGovern Medical School at UTHealth was the lead center in the study, which enrolled patients at centers in Texas, California, Colorado, Illinois and South Carolina. Infants with zone I or posterior zone II ROP were randomly assigned to receive either intravitreal bevacizumab (Avastin®) or conventional laser therapy in both eyes. The results of that landmark Phase II clinical trial were published in the New England Journal of Medicine.1
As a result of positive outcomes of this research, about half of the Level III NICUs across the country are offering bevacizumab for zone I retinopathy of prematurity. Bevacizumab is also being used around the world.
The BEAT-ROP clinical trial is ongoing at McGovern Medical School and other centers. Researchers will publish further conclusions after testing the entire group of study participants when they reach the age of seven.
Follow-up of premature infants with ROP is very important to ensure that the condition is resolved after discharge from the hospital. Also, prematurity may lead to other abnormalities in vision that require long-term follow-up by an ophthalmologist.
1Mintz-Hittner HA, Kennedy KA, Chuang AZ for the BEAT-ROP Cooperative Group. Efficacy of Intravitreal Bevacizumab for Stage 3+ Retinopathy of Prematurity. New England Journal of Medicine 2011, 364:(7);603-615
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