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Physician presents refresher on retinopathy of prematurity
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Retinal vascularization commences at 16 weeks of gestation and finishes around 36 weeks nasally and 40 to 45 weeks temporally. When an infant is born prematurely, retinal vascularization is not yet complete and the infant is predisposed to developing retinopathy of prematurity. The infants most at risk for developing ROP are those born sooner than 30 weeks’ gestational age and less than 1,500 grams. Therefore, the American Academy of Pediatrics and the American Association for Pediatric Ophthalmology and Strabismus, along with the American Academy of Ophthalmology, have devised a protocol for screening at-risk infants for ROP.
Pathogenesis and stages
The pathogenesis of ROP involves two phases. Phase one begins with delayed vasculogenesis after premature birth, resulting in vaso-obliteration when exposed to higher than in utero oxygen concentrations. The levels of VEGF and insulin-like growth factor (IGF) initially fall as the infant is exposed to this hyperoxic environment and lack of maternal factors. The resulting avascular retina leads to phase two, with the rise of VEGF and IGF to create an ischemic phase and abnormal angiogenesis.
ROP consists of five stages. Stage 1 is a demarcation line between vascular and avascular retina. Stage 2 is when the demarcation line turns into a ridge. Stage 3 is neovascularization of the ridge. Stage 4a is a partial retinal detachment with the fovea attached, and stage 4b is a partial retinal detachment with the fovea detached. Stage 5 is a total retinal detachment that can be classified as an open or closed funnel. Plus disease, which is an indicator of severe ROP, is defined as dilated and tortuous vessels at the optic nerve in two quadrants. ROP is also defined by location of the disease, which is divided into three zones. Zone 1 is the most posterior zone encircling the disc and macula by twice the distance from the disc to the macula. Zone 2 includes the peripheral retina extending to the ora serrata nasally. The final zone, zone 3, includes the remaining temporal crescent.
The outcomes of the CRYO-ROP study determined that infants with severe ROP in zone 1 continued to have poor outcomes. Therefore, the Early Treatment for Retinopathy of Prematurity study was completed to revise the treatment criteria and decrease the incidence of poor outcomes. Two types of ROP exist: type 1 high-risk ROP and type 2 low-risk ROP. Type 1 ROP includes those infants with stage 1, 2 or 3 ROP with plus disease or stage 3 ROP without plus disease in zone 1. These infants are considered at high risk, and treatment is recommended. The more mild stages of ROP are considered low risk, and observation for 1 or 2 weeks is recommended, depending on the stage of disease.
Click here to read the publication exclusive, News You Can Use From UPMC Eye Center, published in Ocular Surgery News U.S. Edition, February 10, 2015.