Optical Coherence Tomography Angiography in Eyes with Retinal Vein Occlusion

Abstract

Optical coherence angiography (OCTA) is a noninvasive technique that has been introduced in recent years to detect ophthalmological pathology. The growing usage of OCTA to detect retinal abnormalities can be attributed to its advantages over the reference-standard fluorescein angiography (FA), although both of these techniques can be used in association. OCTA's advantages include its dye independency, its ability to produce depth-resolved images of retinal and choroidal vessels that yield images of different vascular layers of the retina, and the better delineation of the foveal avascular zone. OCTA's disadvantages include the lack of normalized patient data, artefactual projection issues, and its inability to detect low-flow lesions or pathologic conditions. Different OCTA platforms use unique algorithms to detect microvasculature, which are implemented in both spectral-domain (SD) and swept-source (SS) OCT machines. Microvascular changes in retinal vein occlusions (RVOs) are visible in both the superficial and deep capillary networks of the retina in OCTA. These visualizations include a decrease in foveal and parafoveal vascular densities, non-perfusion areas, capillary engorgement and telangiectasias, vascular tortuosity, microaneurysms, disruption of the foveal perivascular plexus, and formation of collateral vessels. The restricted field of view and inability to show leakage are important limitations associated with the use of OCTA in RVO cases. In this article, we present a brief overview of OCTA and a review of the changes detectable in different slabs by OCTA in RVO cases published in PubMed and Embase.

Keywords: Macular Edema; Macular Ischemia; Optical Coherence Tomography Angiography; Retina; Retinal Vascular Disease; Retinal Vein Occlusion.

Figure 1

OCTA (3 × 3 mm) in a case of CRVO. (a) OCTA at the level of the superficial capillary plexus (SCP) showing vascular tortuosity, dilation and telangiectasia (arrow) along with decreased vascular density and non-perfusion areas. Also note the irregular and enlarged foveal avascular zone. (b) En face OCT at the level of the SCP shows the presence of cystoid edema, which corresponds to dark circular areas without vessel signals in OCTA (arrowhead in A). (c) B-scan OCT with perfusion overlay and segmentation lines. (d) Color-coded vascular density map. (e) Numerical report of the vascular density.

Figure 2

OCTA (3 × 3 mm) in a case of CRVO. (a) OCTA at the level of the deep capillary plexus (DCP) showing vascular tortuosity, dilation, and telangiectasia (arrow) along with decreased vascular density and non-perfusion areas. Also note the irregular and enlarged foveal avascular zone. (b) En face OCT at the level of the DCP. Note the presence of cystoid edema corresponding to dark circular areas without vessel signals in OCTA (arrowheads in a). (c) B-scan OCT with perfusion overlay and segmentation lines. (d) Color-coded vascular density map. (e) Numerical report of the vascular density.

Figure 3

OCTA (6 × 6 mm) of a case of BRVO. (a) OCTA at the level of the superficial capillary plexus (SCP) showing vascular tortuosity, dilation and telangiectasia (arrow) along with decreased vascular density and non-perfusion areas in the superotemporal region (a). (b) En face OCT at the level of the SCP. Note the presence of cystoid edema corresponding to dark circular areas without vessel signals in OCTA (arrowhead in a). (c) B-scan OCT with perfusion overlay and segmentation lines showing the level of OCTA in (a). (d) Color-coded vascular density map. (e) Numerical report of the vascular density.

Figure 4

OCTA (6 × 6 mm) of a case of BRVO. (a) OCTA at the level of the deep capillary plexus (DCP). Shunt vessels (arrow) and microaneurysms (arrowheads) are visible in the superotemporal area along with decreased vascular density and non-perfusion areas (a). (b) En face OCT at the level of the DCP. (c) B-scan OCT with perfusion overlay and segmentation lines showing the level of OCTA in (a). (d) Color-coded vascular density map. (e) Numerical report of the vascular density.