Widefield OCTA vasculature visualization in SS-OCT

Abstract

Purpose : Widefield optical coherence tomography angiography (OCTA) imaging is important for visualization of microvascular diseases in peripheral retinal regions. This study demonstrates the OCTA vasculature visualization of superficial (SRL) and deep retinal layer (DRL) as well as choroidal layer (CL) over a scan region of 23 mm x 23 mm captured using an external lens attachment on a swept-source (SS) OCT system.

Methods : A small number of subjects with various stages of diabetic retinopathy or retinal vein occlusion were scanned with the PLEX® Elite 9000 (ZEISS, Dublin, CA) SS-OCT system. Each subject was scanned with an angiography scan (834 x 834 x 3072 pixels) over an area of 15 mm x 15 mm x 6 mm (field-of-view (FOV) ≈ 60°) and an extended area of 23 mm x 23 mm x 6 mm area (FOV ≈ 90°) using an external lens attachment. A prototype multilayer segmentation (MLS) algorithm segmented 9 retinal layers. The segmentation of the inner limiting membrane (ILM) and retinal pigment epithelium (RPE) were calculated based on an iterative method. The regions of ILM and RPE segmentations with low confidence were interpolated to generate complete 2D ILM and RPE segmentations. Other retinal layers were segmented using ILM and RPE as a baseline. ILM, inner plexiform (IPL), outer plexiform (OPL), Bruch’s membrane (BM), and choroidal-scleral junction (CSJ) boundaries were used to generate SRL, DRL, and CL vasculature slabs.

Results : Fig. 1 shows examples of the segmentation of retinal layer boundaries superimposed on the OCT B-scans. The customized MLS algorithm separates the retinal layers which makes the visualization of OCT and OCTA slabs at different depths possible. Fig. 2 shows examples of OCT and OCTA slabs from multiple scans.

Conclusions : We demonstrated OCTA vasculature maps generated over a scan region of 23 mm x 23 mm captured using an external lens attachment. The customized MLS separates retinal layers for more accurate visualization of OCTA vasculature maps. The larger FOV OCTA visualization continues to be an effective alternative to other widefield imaging modalities.

This abstract was presented at the 2023 ARVO Imaging in the Eye Conference, held in New Orleans, LA, April 21-22, 2023.

 

Fig. 1:Structural OCT B-scans with segmented layer boundaries used to generate the slabs (top to bottom: ILM, IPL, OPL, BM, and CSJ).

 

Fig. 2: OCT and OCTA slabs from multiple scans. Top row: Superficial capillary plexus with peripheral ischemia. Middle and bottom rows: Superficial capillary plexus (left), deep capillary plexus (middle), and structural choroidal (right) slabs.