Retinopathy of Prematurity (ROP)
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Title: Retinopathy of Prematurity (ROP)
Authors: Justine Cheng, AB; Charles Calvo, MD and Daniel Churgin, MD, Visiting Instructors, Department of Ophthalmology, University of Utah
Photographer: Moran Eye Center Photography
Keywords/Main Subjects: Retinopathy of prematurity; ROP
Diagnosis: Retinopathy of Prematurity
Brief Description: In the United States, retinopathy of prematurity (ROP) typically affects infants who weigh less than 1500g and born younger than 30 weeks of gestational age. Also at risk are infants who receive supplemental oxygen. In countries where resources for prenatal care and oxygen regulation are not optimal or available, ROP is seen in infants born at higher birth weights and older gestational ages. ROP is characterized by incomplete vascularization of the inner retina. There are three zones of vascularization included in the classification of ROP based on the extent of inner retinal vascularization: zone 1 is the area encompassing a circle centered on the optic nerve and the radius is twice the distance from the optic nerve to the fovea; zone 2 is a circle centered on the optic nerve with a radius from optic disc to the nasal ora serrata; and zone 3 is the remaining temporal crescent. There are five stages that describe the junction between vascular and avascular areas of the retina. In stage 1, this junction is a line. In stage 2, it becomes a ridge with obvious volume. Stage 3 refers to neovascularization extending from the ridge into the vitreous. At stage 4, there is partial retinal detachment, with stage 4A and 4B defined as with and without macular involvement respectively. Finally, in stage 5, there is total retinal detachment (images of the 5 stages are provided below). In addition to the zones and stages, plus disease is another parameter in classifying severity of ROP that is based on arterial and venous dilation and vessel tortuosity at the posterior pole.
The decision to treat an infant with ROP is based on the severity of disease. Historically, threshold ROP was used to signify severe ROP, which is defined as the level of severity that has a 50% of risk of developing unfavorable anatomic outcomes. Prethreshold ROP represented disease severity with high risk of developing threshold ROP. However, treatment is now based on the classification scheme from the ETROP trial (see table 2), which categorizes severe ROP, or type I, as having ≥ 15% risk of developing unfavorable outcomes (see table 1). The diagnosis of type 1 ROP includes the threshold disease.
Age & Gender: Age of onset for most infants is around 32 weeks postmenstrual age (e.g. gestational age plus chronologic age in weeks). When severe ROP develops, it appears between 35 and 37 weeks postmenstrual age.
ROP Symptoms: There are no symptoms that are specific for ROP. Thus, screening is necessary for accurate and timely diagnosis.
Pathophysiology: Retinal vascular development begins around 16 weeks of gestation. Prematurity interrupts this process. Other stresses including high oxygen at birth, fluctuations in oxygenation, poor postnatal growth, oxidative stress can worsen pathology by triggering abnormal angiogenic signaling through vascular endothelial growth factor (VEGF) and other pathways that cause blood vessel to grow into the vitreous instead of into the retina. There are also neurovascular interactions that play into the pathophysiology of ROP.
Treatment: Regulation of oxygen delivery and prenatal care may reduce ROP, but once severe ROP develops, treatment is needed and can include laser or cryotherapy to the avascular retina. Studies are testing the safety and efficacy of compounds that interfere with angiogenic bioactivity including anti-VEGF agents. Below are some of the clinical trials and their roles in ROP management.
Environmental Factors or Other Considerations: There are some elements of neonatal care for premature infants that can affect ROP risk. For example, oxygen use, prenatal steroids can affect risk of ROP, and surfactant use may decrease risk. Other associated risk factors for ROP include intraventricular hemorrhage, infection and inflammation, respiratory distress syndrome, bronchopulmonary dysplasia, and patent ductus arteriosus. Poor postnatal growth may be associated with increased risk of ROP but efforts to improve growth have not reduced ROP severity to date.
Differential Diagnosis: Familial exudative vitreoretinopathy (FEVR), Norrie disease, incontinentia pigmenti, congenital retinal fold, Toxocara canis infection, and causes of leukocoria (including but not limited to congenital cataract, retinoblastoma, infections)
References: The authors acknowledge Wolters Kluwer/ Lippincott Williams and Wilkins [Pediatric retina: medical and surgical approaches. 2nd Ed. Philadelphia: Lippincott Williams & Wilkins, 2005].
Faculty Approval by: M.E. Hartnett, MD