Vessel Density around Foveal Avascular Zone as a Potential Imaging Biomarker for Detecting Preclinical Diabetic Retinopathy: An Optical Coherence Tomography Angiography Study

<b>Purpose</b>: The purpose of this study was to investigate the changes of optical coherence tomography angiography (OCTA) parameters in diabetic retinopathy (DR) using an updated software with 3D projection artifact removal. <b>Methods</b>: In this cross-sectional observational study, 192 eyes of 111 patients with diabetes mellitus (DM) and 55 eyes of 34 age-matched healthy subjects were included. Diabetic patients were divided into three subgroups: without DR, with mild non-proliferative DR, and with moderate-to-severe non-proliferative DR. All eyes underwent dilated fundoscopy along with 3x3mm and 6x6mm OCTA image acquisition. Vessel density (VD), retinal thickness and foveal avascular zone (FAZ) parameters were analyzed. Correlation analyses between OCTA parameters and DR severity were also performed. <b>Results</b>: There was a statistically significant difference in all OCTA parameters among groups, except for superficial foveal VD in 6x6mm scan and whole image retinal thickness in both 3x3mm and 6x6mm scans, while 3x3mm scan parameters were found to be diagnostically superior to the corresponding ones of 6x6mm scan. As the DR stage progressed, the mean VD values decreased. FD-300, which is the VD of a 300-μm width annulus surrounding FAZ, demonstrated the strongest inverse correlation with DR severity (r = −0.590/r_s = −0.562, <i>p</i> p <b>Conclusion</b>: OCTA shows progressive decrease of VD parameters with increasing DR severity. Foveal VD, FAZ area, and perimeter are not very useful indexes due to the high interindividual variability of FAZ size. OCTA and specifically FD-300 may serve as a promising DR screening tool for detecting preclinical microvascular alterations.

<b>研究目的</b>：本研究旨在借助搭载三维投影伪影去除功能的更新版软件，探究糖尿病视网膜病变（diabetic retinopathy, DR）患者的光学相干断层扫描血管成像（optical coherence tomography angiography, OCTA）参数变化。
<b>研究方法</b>：本研究为横断面观察性研究，共纳入111例糖尿病（diabetes mellitus, DM）患者的192只患眼，以及34名年龄匹配的健康受试者的55只健眼。糖尿病患者被分为三个亚组：无视网膜病变组、轻度非增生性糖尿病视网膜病变组，以及中重度非增生性糖尿病视网膜病变组。所有受试者均接受散瞳眼底检查，并完成3mm×3mm与6mm×6mm范围的OCTA图像采集。分析指标包括血管密度（vessel density, VD）、视网膜厚度及黄斑无血管区（foveal avascular zone, FAZ）相关参数。此外还开展了OCTA参数与DR严重程度的相关性分析。
<b>研究结果</b>：各组间除6mm×6mm扫描的中心凹表层血管密度、3mm×3mm及6mm×6mm扫描的全图视网膜厚度外，其余所有OCTA参数均存在统计学显著差异；且3mm×3mm扫描的相关参数诊断效能优于6mm×6mm扫描的对应参数。随着DR病程进展，平均血管密度值逐渐降低。FD-300，即围绕FAZ的300μm宽度环形区域的血管密度，与DR严重程度呈现最强的负相关关系（r = −0.590，r_s = −0.562，*p* < 0.001）。
<b>研究结论</b>：OCTA检测显示，随着DR严重程度升高，血管密度参数呈进行性降低。由于FAZ大小存在较高的个体间差异，中心凹血管密度、FAZ面积及周长并非理想的临床评估指标。OCTA尤其是FD-300有望成为检测临床前期微血管改变的糖尿病视网膜病变筛查工具。