Longitudinal Choroidal Development in Preterm Infants

Abstract

Purpose: To characterize changes in subfoveal choroidal thickness in preterm infants from 30 to 60 weeks' postmenstrual age (PMA).

Design: The prospective, observational Study of Eye Imaging in Preterm infantS (BabySTEPS) enrolled infants eligible for retinopathy of prematurity screening per the American Association of Pediatrics guidelines.

Subjects: Infants imaged with an investigational, handheld OCT at ≥ 4 distinct imaging sessions between 30 to 60 weeks' PMA as part of BabySTEPS.

Methods: Average choroidal thickness across the central subfoveal 1 mm in each eye at each time point was measured using custom segmentation software, and errors were manually corrected by a trained grader. We prospectively collected birth history data. A segmented mixed model was used to analyze the change in choroidal thickness as a function of PMA, birth weight, and gestational age (GA).

Main outcome measures: Characterization of normative subfoveal choroidal thickness values and choroidal growth rate between 30 to 60 weeks' PMA.

Results: We included 592 imaging sessions of 79 preterm infants (152 eyes). Mean (± standard deviation) GA was 27.5 ± 2.5 weeks. Mean choroidal thickness was 141.4 ± 34.5 μm at 30 weeks, 272.2 ± 83.9 μm at 38 weeks, and 306.2 ± 77.4 μm between 56 and 60 weeks. Between 30 and 60 weeks' PMA, choroidal growth followed a biphasic model, with a linear growth rate of 14.8 μm per week (95% confidence interval [CI], 13.6-16.0) from 30 until 38.4 weeks, then cessation of growth, with a growth rate of 0.3 μm per week (95% CI, -1.1 to 1.6) from 38.4 to 60 weeks. Infants with extremely low birth weight (ELBW; < 1000 g) and extremely preterm (GA < 28 weeks) infants had significantly slower initial growth rates compared with very low and low birth weight and very preterm and preterm infants (ELBW 13.0 vs. 21.0 μm per week; P < 0.0001 and extremely preterm 13.2 vs. 18.0 μm per week; P = 0.003).

Conclusions: Preterm infant choroidal thickness experiences rapid linear growth from 30 to 38 weeks' PMA, at which time growth nearly stops. These foundational measurements and identification of the impact of extremes of low birth weight and prematurity on choroidal development will be essential as researchers begin to understand the role of choroidal development in ocular and retinal health in human infants.

Financial disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Choroid; Optical coherence; Premature infant; Tomography.

Figure 1

Longitudinal change in average subfoveal choroidal thickness for all 152 eyes of the 79 infants who were imaged at ≥ 4 time points from 30 to 60 weeks' postmenstrual age. Each dashed line represents the data of an eye. The regression line from the segmented mixed regression model is illustrated by the red line, showing a linear growth rate of 14.8 μm per week from 30 weeks until a transition point at 38.4 weeks, after which growth slows to 0.3 μm per week until 60 weeks. CI = confidence interval.

Figure 2

OCT b-scans from the left eye of a representative infant illustrating the changes in subfoveal choroidal thickness (SFCT) in μm from 34–44 weeks' postmenstrual age (PMA). Panel A illustrates the selection of the fovea (∗) and measurement of the choroidal thickness from the retinal pigment epithelium (solid white line) to the choroidal-scleral junction (tip of the arrows) at several points across the subfoveal 1 mm. Each of these measurements were then averaged to calculate the average choroidal thickness across the central subfoveal 1 mm SFCT.

Figure 3

Longitudinal change in average subfoveal choroidal thickness for (A) infants with extremely low birth weight (ELBW; 81 eyes of 43 infants) versus very low birth weight (VLBW) and low birth weight (LBW; 71 eyes of 36 infants) and (B) infants born extremely preterm (EPT; 75 eyes of 40 infants) versus very preterm and preterm (VPT and PT; 77 eyes of 39 infants). Each dashed line represents the data of an eye. The solid blue and red lines represent the regression lines from the segmented mixed regression models.