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

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

"Coming up short" with an illuminated microcatheter for circumferential trabeculotomy externo in the buphthalmic infant eye: frequency and options.

An illuminated microcatheter is frequently used to perform trabeculotomy ab externo in infants with primary congenital glaucoma (PCG). Enlarged corneas in these children can make it challenging to traverse 360o of Schlemm's canal (SC) before reaching the passable limit of the microcatheter. Using basic geometry, we predicted that the iTrack microcatheter would fail to cannulate SC completely in eyes with a horizontal corneal diameter (HCD) >14.8 mm. A retrospective chart review of patients with PCG undergoing angle surgery identified the frequency of corneas with HCD >14.8 mm and confirmed that this calculated cut-off predicts which eyes can-or cannot-be cannulated successfully (ie, 360o) by the iTrack microcatheter.