Abstract
Purpose :
Multifunctional adaptive optics optical coherence tomography (AO-OCT) allows detailed 3D visualization of axon bundle paths, connective tissues, striated glial partitions, and their intrinsic optical measurements, i.e., reflectance and birefringence, throughout the prelaminar and laminar regions of the ONH in the living human eye. In this study, we have parameterized these features, key biomarkers for glaucoma, by delineating AO-OCT volume images.
Methods :
Multiple 4-second videos of the central ONH were collected from 4 healthy eyes across 3 human subjects using a multifunctional AO-OCT system. Offline volume image reconstruction was used to register and average six to seven hundred volumes. Axonal bundles and striated glial partitions within volumes were manually segmented (Fig.1) and used to measure axon bundle tortuosity, en face pore diameter (PD), nearest neighbor bundle distance (NNBD), and striated glial partition thickness and spacing. Reflectance and birefringence were computed for prelaminar and laminar regions, respectively, to characterize tissue remodeling.
Results :
Mean tortuosity across 4 eyes was 1.98±0.19 (mean±SD), ranged [1.79–2.25], 47.8% more tortuous than those measured in the laminar region of NHPs, ranged [1.16-1.68]1 (p=.0009). Mean PD in the same human eyes was 47.95±6.9 um, 32.5% larger than previous reports (36.2±11.1 µm)2 (p=.04), presumably due to the inclusion of tilted axon bundles. In each subject, mean NNBD followed a similar decreasing trend toward the laminar cribrosa. Once reaching the laminar region, the mean NNBD plateaued or slightly increased. The steep decline of mean NNBD near the surface indicates convergence of axon bundles in the prelaminar region. Mean amplitude reflectance in the prelaminar and laminar regions were similar on average, .027%. Mean birefringence in the laminar region (0.23±0.17 °/µm) was higher than in the prelaminar region (0.14±0.11°/µm) in all eyes. The mean glial spacing was 14.4±2.19 µm with a mean thickness of 2.5 µm.
Conclusions :
AO-OCT imaging has allowed for high-resolution parameterization of the prelaminar region in the ONH, 3D reconstruction of axonal bundles and striated glial partitions, and their intrinsic optical measurements in the living human eye – a great advantage over traditional approaches.
[1] Alexopoulos P, TVST. 2023;12(4):4
[2] Nadler Z, et al. IOVS. 2014;55(10):6459-6466
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.