Relationship between Functional and Structural Changes in Diabetic Vessels in Optical Coherence Tomography Angiography

Abstract

The decorrelation signals in optical coherence tomography angiography (OCTA) are derived from the flow of erythrocytes and concomitantly delineate the retinal vasculature. We compared the structural and functional characteristics of vascular lesions visualized in fluorescein angiography (FA), OCTA, and en-face OCT images in 53 eyes (28 patients) with diabetic retinopathy (DR). The foveal avascular zone (FAZ) areas in OCTA images in the superficial layer almost corresponded to those in FA images. The FAZ areas in the en-face OCT images in the superficial layer were smaller than those in the FA images and correlated with each other, which agreed with the finding that en-face OCT images often delineated the vascular structure in the nonperfused areas in FA images. Microaneurysms appeared as fusiform, saccular, or coiled capillaries in OCTA images and ringed, round, or oval hyperreflective lesions in en-face OCT images. OCTA and en-face OCT images detected 41.0 ± 16.1% and 40.1 ± 18.6%, respectively, of microaneurysms in FA images, although both depicted only 13.9 ± 16.4%. The number of microaneurysms in FA images was correlated with that in OCTA and en-face OCT images. Comparisons of these modalities showed the associations and dissociations between blood flow and vascular structures, which improves the understanding of the pathogenesis of DR.

Can Foveal Avascular Zone (FAZ) Assessment By OCT Angiography, Used For Grading Of Diabetic Retinopathy?

“…This finding may also add to our knowledge regarding pathophysiology behind the ischemic changes in DR. The OCTA has increased feasibility of qualitative FAZ assessment; but the most impressing are regarding the quantitative FAZ assessments the FAZ size increased significantly by progression of retinopathy grade in almost all reports [9][10][11][12][13][14][15][16][17]. (Table 1) has summarized current available range of the mean FAZ size values in different grades of disease.…”

“…Our center reviewed literature regarding the OCTA applications in diabetics which is going to be published soon. Available reports are few, but interesting facts regarding the FAZ is published [7][8][9][10][11][12][13][14][15][16][17][18]. The FAZ in normal individual was described in the OCTA as an intact well-demarcated round or oval area of reduced capillary density with a border without gaps, holes or interruption of the capillary network in both superficial and deep plexuses.…”

“…Furthermore, the FAZ is enlarged in diabetics not only before developing to apparent DR but even before systemic diagnosis of DM, so it could also be used as a predictor for whom may need closer follow up [11,15]. Putting these findings alongside our previous knowledge regarding the FAZ characteristics such as being considered as a vascular index and correlated to presumed ischemic pathophysiology behind DR; being correlated with VA in DR [9,19]; being able to help treatment selection as DME patients with larger FAZ was reported to be non-responder to laser therapy, who may benefit more from Anti-VEGF treatments [20]; being influenced by treatment modalities (laser or Anti-VEGF therapies) that may lead to reperfusion and reduce the FAZ area [17]; these altogether propose the FAZ characteristics as a potential qualitative and quantitative index that not only can be used to grade the DR but also to predict DR, guide the selection of appropriate treatment, help to localize laser treatment targets and follow up the effect of treatment. It should be pointed out that before introduction of the OCTA, the FAZ qualitative and quantitative specifications could not be accurately and reliably assessed.…”

Descriptive Case Series on Optical Coherence Tomography Angiography Findings of Patients with Idiopathic Intermediate Uveitis in a Referral Ophthalmological Centre at Mexico City

“…Recently faster scan rates and higher resolutions have made possible the wide spread clinic use of OCTA. Several studies have validated its reproducibility and made correlations between FA and OCTA [9,11]. More studies are needed to evaluate the practical use of OCTA in the daily practice to diagnose and follow retinal vasculature abnormalities in diseases such as IIU [9].…”

The Effect of Aflibercept and Ranibizumab in Patients with Diabetic Macular Edema: A comparative Study

“…It may cause several complications, such as diabetic macular edema (DME) and diabetic macular ischemia (DMI). In particular, capillary non perfusion impairs the nutrition of the neuroglial tissues in the retinal parenchyma, and the resultant hypoxia increases the expression of vascular endothelial growth factor (VEGF), which promotes both angiogenic responses and vascular permeability (5) .…”