What is Retinopathy of Prematurity?
Retinopathy of prematurity (ROP) occurs in premature babies when abnormal blood vessels and scar tissue grow over the retina. ROP is a major cause of blindness throughout the world. The incidence of ROP is increasing as more extremely low-birth-weight babies are surviving due to advances in medical technology and therapeutics.
Premature infants with ROP do not have symptoms. External signs develop only after the disease has become severe or progressed to retinal detachment. Timely detection of ROP depends upon examination by an ophthalmologist experienced in the examination of premature infants.
The causes of ROP are not completely understood. During a full-term pregnancy, the blood vessels in the retina become fully formed by birth. In premature babies, the blood vessels are immature at birth and the retina produces abnormal levels of various factors important during eye development, including vascular endothelial growth factor (VEGF) to produce more blood vessels. However, the resulting vessels are abnormal and may lead to bleeding and, ultimately, retinal detachment and permanent blindness.
Risk factors for the development of ROP include prematurity, extremely low-birth-weight, and multiple births. Life-long follow-up is necessary in people who have had ROP, even those who did not require treatment. Myopia, strabismus, and retinal detachment are common in patients with ROP.
Tests and Diagnosis
At-risk babies are screened at various intervals determined by extensively studied practices and procedures. Repeat dilated eye exams are required even after discharge from the NICU setting.
Treatment and Drugs
Approximately 10 percent of babies screened will require treatment. Laser photocoagulation has long surpassed cryotherapy as the standard of care. Laser spots are placed in the areas of retina that failed to develop normal blood vessels, in an attempt to slow down or reverse the growth of abnormal blood vessels and scar tissue formation. Retinal laser is performed when ROP has progressed to a point that meets strict guidelines for treatment, published jointly by the American Academy of Pediatrics, American Association for Pediatric Ophthalmology and Strabismus, and American Academy of Ophthalmology.
Recent research studies have shown that bevacizumab, a medication that blocks VEGF when injected directly into the eye, may be an alternative treatment in a small number of premature infants with ROP. Bevacizumab appears to cause abnormal vessels to regress thereby preventing bleeding and retinal detachment. In many large centers in the U.S, including the University of Michigan, bevacizumab treatment is reserved for premature infants who cannot tolerate the laser procedure because of their other life-threatening conditions, visualization of the retina is obscured preventing adequate laser treatment, or in extremely premature infants with an aggressive form of ROP that has a high chance of progressing to retinal detachment despite laser treatment. The long-term side effects of this treatment are unknown. Further studies are necessary to understand the effects of bevacizumab in lung and brain development, two other organs that depend heavily on VEGF function during normal development.
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Reviewed by Cagri G. Besirli, M.D., Ph.D.