Factors Inf luencing Refractive Development in Early Stages of Prematurity

Abstract

Objective: To investigate the refractive status of premature infants with a postmenstrual age of 32 to 40 weeks, and to identify factors (birth weight, gestational age, retinopathy of prematurity) contributing to refractive status. Methods: A prospective study of the refractive status of preterm infants was conducted at the Women's Hospital School of Medicine, Zhejiang University and the Eye Hospital of Wenzhou Medical University from March to December 2016. The infants were recruited from ascreening program for retinopathy of prematurity (ROP) performed on premature infants. Examinations were performed longitudinally at the postmenstrual age of 32 to 40 weeks. Full cycloplegic retinoscopy was performed on the right eyes. Refractive status was recorded in the form of spherical equivalent (SE). Birth weight, gestational age, gender, oxygen and postmenstrual age were recorded for further analyses. Pearson correlation analysis was conducted to study the relationship between SE and multiple factors (birth weight, gestational age, postmenstrual age). An independent samples t test was used to study the relationship between SE and ROP at the postmenstrual age of 40 weeks. Results: A total of 542 refractive status readings were recorded from 333 infants (158 females, 175 males) between the postmenstrual age of 32 to 40 weeks. The gestational age of the infants ranged from 26 to 36 weeks (mean: 31.3±2.1 weeks), and birth weight ranged from 740 to 3 390 g (mean: 1 643±418 g). The SE was positively correlated with the postmenstrual age of the infants (r=0.455, P<0.001). Gestational age (r=0.373, P<0.001) and birth weight (r=0.345, P<0.001) were both positively correlated with refractive status between the postnatal age of 4 to 5 weeks. By the postmenstrual age of 40 weeks, the SE was positively correlated with birth weight (r=0.197, P=0.021). However, there was no statistically significant difference between SE and gestational age. And premature infants with ROP were more myopic than those without ROP (t=2.225, P=0.028). Conclusions: During the early stages of postmenstrual age of 32 to 40 weeks, there is a positive increase in the SE as postmenstrual age increases. Premature infants with low gestational age and low birth weight are more myopic between the postnatal age of 4 to 5 weeks. By the postmenstrual age of 40 weeks, premature infants with low birth weight or with ROP are more myopic. Key words: refractive status; factors; premature infants