In Vivo Wide-Field OCT Imaging Reveals and Quantifies a Hyporeflective Band beneath Bowman's Layer

To investigate the anterior corneal region immediately beneath Bowman's layer using wide-field self-referenced optical coherence tomography (OCT) and to identify and characterize a distinct hyporeflective band at the Bowman's layer-anterior stroma interface.

Seventeen eyes from 17 healthy subjects were analyzed with a custom wide-field spectral-domain OCT system in a self-referenced common-path configuration. Eighteen radial scans over a 9-mm corneal diameter were acquired and processed. A segmentation framework was developed to identify the boundaries of the epithelium, Bowman's layer, hyporeflective band, and total cornea. Thickness maps were generated and analyzed across four anatomical zones. Repeatability was assessed using repeated segmentations.

A thin, continuous hyporeflective band (HB) immediately beneath Bowman's layer was consistently visualized across the corneal field in all 17 eyes analyzed. Mean HB thickness was approximately 8 µm, with slightly greater central than peripheral values. However, zonal differences remained within measurement repeatability. Thickness of the epithelium and Bowman's layer showed minimal spatial variation within measurement precision.

Wide-field self-referenced OCT enables in vivo visualization and quantitative assessment of a distinct hyporeflective band at the Bowman's layer-anterior stroma interface, providing a measurable optical signature of the anterior cornea.

Wide-field self-referenced OCT provides noninvasive, in vivo access to a corneal region previously characterized mainly by ex vivo or highly localized methods. This capability enables future studies examining whether the hyporeflective band is altered in corneal disease.