The following is a summary of “OCT Optic Nerve Head Morphology in Myopia III: The Exposed Neural Canal Region in Healthy Eyes – Implications for High Myopia,” published in the September 2023 issue of Ophthalmology by Hong et al.

Researchers performed a retrospective study to determine the prevalence and magnitude of OCT exposed neural canal (ENC), externally oblique choroidal border tissue (EOCBT), and exposed scleral flange (ESF) regions in 362 eyes of 362 healthy subjects with non-highly myopia (spherical equivalent -6.00 to 5.75 diopters).

They manually segmented Bruch’s membrane opening (BMO), the anterior scleral canal opening (ASCO), and the scleral flange opening (SFO) after OCT optic nerve head (ONH) imaging. These points were projected to the BMO reference plane, and the direction and magnitude of BMO/ASCO offset were determined. The ENC, EOCBT, and ESF volumes were calculated within 30° sectors relative to the Foveal-BMO axis. Hi-ESF eyes had an ESF ≥ 100 µm in at least one sector. Sectoral perineural canal choroidal thickness (pNC-CT) was measured, and correlations between sectoral ESF magnitude and proportional pNC-CT were examined.

The results showed 73 Hi-ESF eyes (20.2%) and 289 Non-Hi-ESF eyes (79.8%). In the inferior temporal region where pNC-CT was thinnest, BMO/ASCO offset, ENC, EOCBT, and ESF prevalence and magnitude were highest. Among Hi-ESF eyes, the volume of each ENC region correlated with BMO/ASCO offset magnitude, and sectors with the longest ESF correlated with proportionally thinner pNC-CT in those sectors.

They concluded that ONH BMO/ASCO offset corresponds with ESF and minimum pNC-CT in non-highly myopic eyes.

 Source: ajo.com/article/S0002-9394(23)00338-0/fulltext