Biphasic change in retinal nerve fibre layer thickness from 30 to 60 weeks postmenstrual age in preterm infants

Abstract

Background/AimsThe optic nerve development during the critical postnatal weeks of preterm infants is unclear. We aimed to investigate the change of retinal nerve fibre layer (RNFL) in preterm infants.MethodsWe used an investigational handheld optical coherence tomography (OCT) system to serially image awake preterm infants between 30 and 60 weeks postmenstrual age (PMA) at the bedside. We assessed RNFL thickness in the papillomacular bundle and nasal macular ganglion cell layer+inner plexiform layer (GCL+IPL) thickness. We applied a segmented mixed model to analyse the change in the thickness of RNFL and GCL+IPL as a function of PMA.ResultsFrom 631 OCT imaging sessions of 101 infants (201 eyes), RNFL thickness followed a biphasic model between 30 and 60 weeks, with an estimated transition at 37.8 weeks PMA (95% CI: 37.0 to 38.6). RNFL thickness increased at 1.8 μm/week (95% CI: 1.6 to 2.1) before 37.8 weeks and decreased at −0.3 μm/week (95% CI: −0.5 to −0.2) afterwards. GCL+IPL thickness followed a similar biphasic model, in which the thickness increased at 2.9 μm/week (95% CI: 2.5 to 3.2) before 39.5 weeks PMA (95% CI: 38.8 to 40.1) and then decreased at −0.8 μm/week (95% CI: −0.9 to −0.6).ConclusionWe demonstrate the feasibility of monitoring RNFL and GCL+IPL thickness from OCT during the postnatal weeks of preterm infants. Thicknesses follow a biphasic model with a transition age at 37.8 and 39.5 weeks PMA, respectively. These findings may shed light on optic nerve development in preterm infants and assist future study designs.

Preterm infant retinal OCT markers of perinatal health and retinopathy of prematurity

“…RNFL thickness in preterm infants follows a biphasic pattern of change between 30 and 60 weeks PMA. In BabySTEPS, we found that the RNFL thickness increases at 1.8 µm/week from 30 to 37.8 weeks PMA and then decreases at −0.3 µm/week from 37.8 to weeks PMA ( 41 ). We did not find an association between RNFL thickness and macular edema in either BabySTEPS or our earlier report with Rothman et al ( 20 , 41 ).…”

“…In BabySTEPS, we found that the RNFL thickness increases at 1.8 µm/week from 30 to 37.8 weeks PMA and then decreases at −0.3 µm/week from 37.8 to weeks PMA ( 41 ). We did not find an association between RNFL thickness and macular edema in either BabySTEPS or our earlier report with Rothman et al ( 20 , 41 ). This understanding of the biphasic thickness change may be useful when evaluating the longitudinal impact of diseases such as ROP and interventions such as ROP treatment on infant retinal development.…”

Longitudinal Choroidal Development in Preterm Infants

“… 12 , 17 , 18 Both RNFL thickness and axial length undergo rapid growth until approximately 38 to 42 weeks or around the time an infant would be considered full-term, after which grow slows dramatically. 6 , 7 , 8 Similarly, the retinal vasculature grows rapidly until 36 weeks nasally and 40 weeks temporally, at which time the retina is considered fully vascularized. The signaling molecules underlying this abrupt TP near term followed by slower growth rate post 40 weeks remain unclear.…”

“…We have previously applied this segmented mixed model to analyze the change of RNFL thickness. 6 Statistical significance was defined as 2-sided P < 0.05.…”

“…Retinal nerve fiber layer (RNFL) thickness follows a bimodal distribution, with more rapid growth peaking at 38 weeks and then slowly thinning. 6 Axial length follows a parabolic curve, growing rapidly until around 38 to 42 weeks, then much more slowly thereafter. 7 , 8 Given the previous findings by Moreno et al, 5 we predicted the choroid would grow linearly until at least 44 weeks' PMA but were unsure if the choroidal thickness would continue to increase after that or would slow, similar to the growth curves we had observed for other ocular structures.…”