Full Circumferential 3D Reconstruction of Schlemm’s Canal in Living Human Using Megahertz Swept Source OCT

Abstract

Purpose : Schlemm’s canal (SC), a ring-shaped structure encircling the cornea, is responsible for intraocular pressure regulation and plays an important role in the onset and progression of glaucoma. This study explores the possibility of full circumferential three-dimensional (3D) reconstruction of SC in living human by using a megahertz (MHz) swept-source optical coherence tomography (OCT) prototype at 1060nm for motion-free SC imaging and a semi-automatic algorithm for SC segmentation from the OCT intensity images.

Methods : Eight volumetric scans were acquired around the limbus of both eyes of one healthy volunteer. Each scan was located at one of the cardinal and intercardinal positions to fully cover the SC. An external fixation target was introduced to ensure normal incidence at the corneal surface at each position. The fast scan was along the longitudinal direction of the SC at each of the cardinal positions, while kept in horizontal direction at the intercardinal position. Each volume took less than one second to complete. The OCT B-scans that contain SC were selected and processed for segmentation. A semi-automatic active contour segmentation algorithm was implemented and the segmented 3D SC mask from each volume was stitched. Quantitative metrics derived from the 3D segmentation were presented and analyzed.

Results : Figure 1 shows the rendering of the stitched SC segmentation for both eyes. The rapidly changing size as well as the branching of collector channels was faithfully depicted in the 3D reconstruction. Table 1 summaries the quantitative metrics. The mean cross-sectional area (CSA) as well as the maximum opening of SC was highest in the superior position in the right eye, while temporal-superior in the left. The tendency of increased collector channels in the inferior quadrant compared to the superior was noticed as well.

Conclusions : We demonstrated full circumferential SC imaging using 1060 nm MHz SS-OCT in living human eyes without motion artifacts. The semi-automatic active contour segmentation algorithm was applied in the B-scans along the longitudinal direction of the SC, which yielded reliable 3D SC segmentation results. The full circumferential imaging and segmentation of SC enabled more sophisticated analysis of SC morphology, offering a new way for examination of the aqueous outflow pathway.

This is a 2021 ARVO Annual Meeting abstract.

 

Figure 1

 

Table 1