Birth Weight Is a Significant Predictor of Retinal Nerve Fiber Layer Thickness at 36 Weeks Postmenstrual Age in Preterm Infants

Abstract

To assess retinal nerve fiber layer (RNFL) thickness in preterm infants. Prospective observational study. We imaged 83 awake infants (159 eyes) at 36 ± 1weeks postmenstrual age (defined as the time elapsed between the first day of the last maternal menstrual period and the time at imaging) using a handheld optical coherence tomography (OCT) system at the bedside. Blinded graders semi-automatically segmented RNFL in the papillomacular bundle (-15 to+15° relative to the fovea-optic nerve axis). We correlated RNFL thickness and 7 characteristics of interest (sex, race, ethnicity, gestational age, birth weight, stage of retinopathy at prematurity, and presence of pre-plus or plus disease) via univariable and multivariable regressions. RNFL was 3.4μm thicker in the right eyes than in the left eyes (P < .001). Among 7 characteristics, birth weight was the only independent predictor of RNFL thickness (P < .001). A 250-g increase in birth weight was associated with 5.2μm (95% confidence interval: 3.3-7.0) increase in RNFL thickness. Compared with very preterm infants, extremely preterm infants had thinner RNFL (58.0 ± 10.7μm vs 63.4 ± 10.7μm, P= .03), but the statistical significance disappeared after adjustment for birth weight (P= .25). RNFL thickness was 11.2μm thinner in extremely low birth weight infants than in very low birth weight infants (55.5 ± 8.3μm vs. 66.7 ± 10.2μm; P < .001). The difference remained statistically significant after adjustment for gestational age. Birth weight is a significant independent predictor of RNFL thickness near birth, implying that the retinal ganglion cells reserve is affected by intrauterine processes that affect birth weight.