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Retinopathy of prematurity (ROP) is a disorder that affects the
developing retinal blood vessels of premature infants. It the leading
cause of acquired childhood blindness in the United States. The
disease was first recognized in the 1940s1 and
was initially thought to be due to the normal primitive vascular
system in the vitreous cavity persisting in an abnormal fibrotic
state.2 By 1952, ROP became recognized as an acquired
disease,3 and in 1955, the role of excessive supplementary
oxygen for premature infants was proven to be a significant causative
factor.4 Despite many improvements in neonatal
care practices, ROP continues into the 21st century as a major complication
of premature birth.
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In the data of the CRYO-ROP study, black infants demonstrated
65% lower odds of reaching severe ROP in need of treatment.5 The
reason for this is unclear,6 but genetic influences
are a possibility. In addition, there are relatively rare genetic
disorders of the eye with similarities to ROP, including familial
exudative vitreoretinopathy (FEVR), Norrie disease, and incontinentia
pigmenti. The main pediatric retinal vascular diseases to distinguish
from ROP are considerably more rare than ROP. Premature infants
at risk for ROP undergo routine ophthalmologic examination, so,
in general, the ability to observe the classical appearance and
development of ROP allows a firm diagnosis. Polymorphisms of the
X-linked recessive gene, which when mutated is associated with Norrie
disease, have been suggested as a predisposing factor for ROP; however,
this has not been replicated by all investigators. Thus, although
ROP is generally considered to be nonhereditary, genetic factors
are possible.
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The development of ROP usually correlates with the overall extent
of medical illnesses and complications associated with prematurity, such
as patent ductus arteriosus, bronchopulmonary dysplasia, acidosis,
anemia, blood transfusion, infection, necrotizing enterocolitis, and
intracranial hemorrhage. Medical risk factors are dominated by the
fact that the incidence and severity of ROP increase inversely with birth
weight and gestational age.7 Full-term infants
rarely, if ever, develop significant ROP. During the past several
decades, the main epidemiological change observed in the United
States has been a lower incidence/severity of ROP among higher-gestational-age
premature infants. However, at the same time, an increased survival
rate for less mature infants has produced a new, less-mature population
at risk.
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In the United States, problematic ROP appears essentially to
be limited to infants with birth weights less than 1500 g. As of
the early part of this millennium, the average birth weight for
US infants requiring treatment for ROP is about 800 g.8 ROP
occurs in about two thirds of infants born weighing 1250 g or less.7,9 In
that same group, about 10% require treatment.
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In utero, the normally developing human retinal vasculature proceeds
centrifugally outward from the optic nerve head, reaching the ora
serrata on the nasal side of the eye by about the full gestational
term of 38 to 40 weeks. The vessels reach ...