The role of optical coherence tomography angiography in fundus vascular abnormalities

Abstract

Background: To evaluate the role of optical coherence tomography angiography (OCTA) in observation of fundus vascular abnormalities.

Methods: Patients (n = 50, 10 in each group) with fundus disorders including branch retinal vein occlusion (BRVO), non-proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR), exudative age-related macular degeneration (AMD), and polypoidal choroidal vasculopathy (PCV) were examined. They underwent imaging of OCTA and fluorescein angiography/indocyanine green angiography. The split-spectrum amplitude-decorrelation angiography algorithm was employed to obtain angiography within a 6 × 6 mm scanning area at the posterior retina. Segmentation algorithm was used to obtain 2-dimensional images from arbitrary layers. The OCTA features were analyzed and compared with the findings of conventional angiography. The contralateral eyes of the patients with BRVO and the eyes of 20 healthy volunteers served as controls.

Results: OCTA showed precise images of normal and abnormal vasculature in the posterior retina and choroid by the given layers. Vascular abnormalities such as enlarged foveal avascular zone (FAZ), non-perfusion area of retina, microaneurysm, retinal neovascularization, choroidal neovascularization (CNV), branching vascular network and polypoidal lesions in choroid were clearly displayed by OCTA.

Conclusions: OCTA provided a better projection of vascular pathologies of the posterior retina and choroid and could determine the precise location of the vascular lesion. The noninvasive OCTA can benefit the diagnosis of vascular abnormalities in the posterior retina and choroid.

Keywords: BRVO; CNV; DR; Fundus vascular abnormalities; Optical coherence tomography angiography; PCV.

Figures

Fig. 1

Normal retinal vasculature and retinal vascular abnormalities showing by OCT angiograms. The normal appearance of the superficial (a1) and deep (a2) vascular plexus showed an intact fovea avascular zone (FAZ) surrounding by distinct and homogeneous web-like retinal vascular networks. Large retinal vessels in the superficial vascular plexus were reflected onto the deep vascular plexus (a2). The early phase of normal FA image was shown in (a5). FAZ was enlarged and extended superiorly (b1, b2) and temporally (c1, c2). Both the superficial and the deep vascular plexuses were affected. The nonperfusion areas were revealed superotemporally to the fovea and the vascular meshes became sparse and irregular with the tortuous and dilated residual capillaries (b1, b2). Microaneurysms showed as hyperreflective dots around the FAZ in both the superficial vascular plexus (c1) and the deep vascular plexus (c2). Retinal neovascularization was mainly located prior to the superficial vascular plexus (d1), distinctively delineated as flower-like branching loops. The nonperfusion areas in FA image (b5) seemed less profound than those in OCT angiograms. Microaneurysms were better illustrated in FA image (c5). The enlarged FAZs (b5, c5) and retinal neovascularization (d5) in FA images appeared identical in shape with those in corresponding OCT angiograms. The double lines in B scan OCT images of a3, a4, b3, b4, c3, c4, d3, and d4 indicated the layers exhibited in a1, a2, b1, b2, c1, c2, d1, and d2 respectively. (Yellow dashed line: FAZ; Green dashed line: retinal nonperfusion area; Red arrowhead: microaneurysm; Red dashed line: retinal neovascularization)

Fig. 2

Normal choroidal vasculature and choroidal neovascularization (CNV) showing by OCT angiograms. The normal appearance of the outer retina showed in absence of blood flow (a1). The normal appearance of the choroid capillary showed with homogeneous grayish capillary beds (a2). The early phase and the late phase of normal FA images were shown in (a5) and (a6) respectively. Hyperreflective CNVs were demonstrated at both the outer retina level (b1, c1) and the choroid capillary level (b2, c2). The configurations of these CNV lesions were strikingly identical with those in the early phase of FA (b5, c5). CNV was in a globular aspect in (b1) and (b2), while in a fan-like shape with a feeder vessel in (c1) and (c2). The hyporeflective speckles (white arrowheads, b2) regarding the hard exudates were “mirror images” projected from the deep retinal plexus layer (not shown). The early phase of FA (b5, c5) revealed hyperfluorescent CNVs, while the late phase of FA (b6, c6) showed leakage and edema caused by CNV. The double lines in B scan OCT images of a3, a4, b3, b4, c3, and c4 indicated the layers exhibited in a1, a2, b1, b2, c1, and c2 respectively. (Yellow dashed line: CNV; White arrow head: “mirror image” of hard exudate)

Fig. 3

Branching vascular networks (BVNs) and polypoidal lesions showing by OCT angiograms. The hyperreflective BVNs were primarily located at the choroid capillary level (a2, b2). BVNs were faint or absolutely fade out at the outer retinal level (a1, b1). The polypoidal lesion was a cluster of hyperreflective, medium or hyporeflective spots (red dashed circles in a2 and b2). On ICGA images, polypoidal lesions showed as clusters of hyperfluorescent spots (red dashed circles in a5 and b5) in connection to the ends of BVNs. The double lines in B scan OCT images of a3, a4, b3, and b4 indicated the layers exhibited in a1, a2, b1, and b2 respectively. (Yellow dashed line: BVN; Red dashed line: polypoidal lesion)