Abstract
Purpose :
The neurosensory retina contains a large variety of vasculature. Changes thereof, for example in the thickness of vessel walls may serve as early biomarker for various diseases such as diabetic retinopathy. This study investigates the capabilities of adaptive optics optical coherence tomography (AO-OCT) to visualize epi-vascular structures on a cellular level.
Methods :
A pyramid wavefront sensor based spectral domain AO-OCT instrument operating in the 840nm wavelength range was used for imaging. The A-scan rate of the system was 250kHz and volume scans consisting of 750x750 pixels that cover an area of 4° (x) by 4° (y) were recorded in 2.5 seconds. No volume averaging was required to produce the image data. The loop speed of the AO was 30Hz and a novel focus shifting method was incorporated for stable imaging of the anterior layers. To cover a larger field of view that spans along the superior vessel arc, 8-10 volume recordings were stitched together. This allows for an observation of the vessels over a larger extension. The total imaging session time including subject alignment and three different focus settings was below 20 minutes.
Results :
Representative image data is shown in Figs. 1 and 2. In this subject, the vessel walls of arteries and veins could be resolved along the vessel arc with a vessel wall thickness ranging from 5µm to 12µm for the arteries and 2µm to 5 µm for the veins, respectively. Adjacent to the arteries, hypo-reflective structures in the order of 100µm can be seen (cf. Fig. 1D,E,F). Adjacent to veins, cellular hypo-reflective structures of 10µm size (cf. Fig.2c) can be observed. Hyper-reflective foci of ~5µm diameter appear wihthin the vessel walls.
Conclusions :
The new focus shifting method allows for stable imaging of anterior retinal layers and a for a larger applicability of AO-OCT. Various epi-vascular structures that are hypo- or hyper-reflective can be visualized using AO-OCT. These structures may serve as biomarker for the early onset of a vascular disease such as diabetic retinopathy. However, the anatomic correspondence of these structures is currently unclear and needs further investigations.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.