Determining relative thickness of inner retinal layers on single-line foveal optical coherence tomography (OCT) in healthy pediatric eyes—normative data for handheld OCT

Abstract

Handheld optical coherence tomography (HH-OCT) lacks integrated segmentation/analysis software. Optic neuropathies cause ganglion cell layer (GCL) thinning, with normal to thickened inner nuclear layer (INL), suggesting the potential value of estimating the GCL/INL ratio on single-line foveal HH-OCT scans. This study determines this ratio in macular scans from healthy eyes of young children using HH-OCT and overhead-mounted OCT. Macular OCT scans were obtained using either HH-OCT or overhead-mounted Spectralis FLEX-OCT in children ages 0-5 years undergoing clinically indicated anesthesia/sedation. Exclusion criteria included gestational age <37 weeks, neurologic disease, amblyopia, ocular disease, or large refractive error (spherical equivalent beyond -3.00 D to +8.00 D). For HH-OCT, the GCL and INL were manually measured in pixels from single-line macular scans at the thickest point nasal and temporal to the fovea. For FLEX-OCT images, measurements were aided by automated software. HH-OCT was obtained on 38 eyes (38 children, mean age 2.4 ± 1.8 years) and FLEX-OCT on 56 eyes (56 children, mean age 2.3 ± 1.5 years). Mean nasal GCL/INL was 1.24 ± 0.18 (min/max = 0.92/1.75) for HH-OCT and 1.29 ± 0.18 (min/max = 0.96/1.66) for FLEX-OCT (P = 0.11). Mean temporal GCL/INL was 1.22 ± 0.24 (min/max = 0.66/1.70) for HH-OCT and 1.19 ± 0.16 (min/max = 0.86/1.47) for FLEX-OCT (P = 0.47). Mean normative GCL/INL ratios were approximately 1.2 at the thickest macular areas both nasal and temporal to the fovea, with either HH-OCT or FLEX-OCT in young children's eyes. These values may prove useful when HH-OCT is used to assess optic neuropathies, in which the GCL/INL ratio is expected to be decreased.