influence the development of ROP, such as the
use of supplemental oxygen after birth, blood
transfusion, sepsis, and apnea. However, ROP
does occur in the absence of these factors. According to Agarwal et al., "In general,
more than 50% of preterm infants weighing less
than 1250 g [2.75lbs.] at birth show evidence of
ROP and about 10% of the infants develop severe ROP" (Agarwal, Azad, Chandra, Chawla,
Deorari, & Paul, 2012). Shastry estimates that
the incidence of ROP is 68% of infants weighing
less than 1251 g and 98% of those weighing less
than 750 g (1.65 lbs.) (Shastry, 2010).
Increased Prevalence of Preterm Birth
Prematurity is defined as an infant born before 37 weeks. The percentage of preterm births
in the United States in 2010 was 11.99% according to the CDC (Hamilton, Martin, & Ventura,
2011). However, there is some debate as to the
accurate definition of gestational age (GA) due to
inconsistencies in the starting point of this measurement. If the GA is calculated to correspond to
the mother's reported date of her last menstrual
period (LMP), plus 14 days (the typical time of
ovulation), there is room for error. The error can
occur due to the mother's incorrect recollection of
the date of the LMP, or due to fluctuations in the
actual time of ovulation in individuals. If age is
determined by other measurements, such as the
length of the fetus via ultrasound, or the height of
the mother's fundus, these are estimations and
also allow for error (Barros, et al., 2012). This is
important in the treatment and diagnosis of ROP,
because there is a specific progression of the disease in the preterm infant after birth, according to
the GA of the infant, which is detailed later in this
paper. ROP occurs in early preterm infants
whose eyes are still developing. The vascularization of the eyes occurs between weeks 16 and 36
41
