PURPOSE To study the retinal capillary microvasculature and the choriocapillaris (CC) in myopic eyes using swept-source optical coherence tomography angiography (SS-OCTA). METHODS Patients with high myopia (≥ - 6D; axial length ≥ 26.5 mm), moderate myopia (≥ - 3D, < - 6D), and age-matched healthy subjects presenting to the Shanghai General Hospital and Doheny-UCLA Eye Centers were enrolled in this prospective, multicenter study. Any subjects with evidence of macular abnormalities suggestive of pathologic myopia were excluded. SS-OCTA at both sites was performed using a Zeiss PLEX Elite instrument with a 6 × 6 mm scan pattern centered on the fovea. Two repeated volume scans were acquired for image averaging. The instrument pre-defined en face slab of the superficial and deep retinal capillary microvasculature was used to isolate and display the superficial and deep retinal capillaries. A slab spanning from 21 to 31 μm deep to the RPE fit line was used to isolate and display the CC. The OCTA images were exported for averaging using Image J. Littmann's method and the Bennett formula were applied to adjust for the impact of magnification in the high and moderate myopia groups. The resultant images were then binarized. Though projection artifact removal software was used, regions below the large superficial retinal vessels were excluded for quantitative analyses of the deep retinal capillary plexus and the CC. Vessel density (VD) and vessel length density (VLD) of the superficial and deep retinal capillary plexus (SCP, DCP) and CC flow deficit (FD) were analyzed, quantified, and compared between different groups. RESULTS Twenty-five eyes of 25 patients with high myopia, 25 eyes of 25 patients with moderate myopia, and 25 eyes of 25 normal age-matched controls were included in this study. The VD of the SCP was lower in the high myopia group compared with the emmetropic control groups (p < 0.05), but the VD of the DCP demonstrated no significant difference among the three groups (p > 0.05). The VLDs of the SCP were lower in the high and moderate myopia groups compared with the control group (p < 0.05), while the VLD of the DCP was lower in the high myopia group compared with the moderate myopia and emmetropic control group (p < 0.05). The CC FD% in the high myopia group was significantly greater than both the control and moderate myopia subjects (p < 0.05). Of note, the severity of the CC flow deficit was not correlated with choroidal thickness (p > 0.05). CONCLUSION The retinal microvasculature may demonstrate alterations in highly myopia eyes. The CC in macular regions shows greater impairment in eyes with high myopia compared with eyes with lesser degrees of myopia, and these deficits are already present in the absence of features of pathologic or degenerative myopia. The threshold of CC FD leading to myopic maculopathy remains to be defined.

中文翻译：

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使用扫描源光学相干断层扫描血管造影术对近视患者的视网膜微血管系统和脉络膜毛细血管进行定量评估。

目的使用扫频源光学相干断层扫描血管造影术 (SS-OCTA) 研究近视眼的视网膜毛细血管微血管系统和脉络膜毛细血管 (CC)。方法 高度近视（≥ - 6D；轴长≥ 26.5 mm）、中度近视（≥ - 3D，< - 6D）和年龄匹配的健康受试者在上海总医院和 Doheny-UCLA 眼科中心就诊。这项前瞻性、多中心研究。排除具有提示病理性近视的黄斑异常证据的任何受试者。两个部位的 SS-OCTA 均使用 Zeiss PLEX Elite 仪器进行，扫描模式为 6 × 6 mm，以中央凹为中心。获得两次重复的体积扫描以进行图像平均。使用仪器预定义的表层和深层视网膜毛细血管微血管系统分离和显示表层和深层视网膜毛细血管。使用从 21 到 31 μm 深到 RPE 拟合线的平板来隔离和显示 CC。使用 Image J. Littmann 方法导出 OCTA 图像进行平均，并应用 Bennett 公式来调整高度和中度近视组放大率的影响。然后对所得图像进行二值化。尽管使用了投影伪影去除软件，但在对视网膜深部毛细血管丛和 CC 进行定量分析时，大表层视网膜血管下方的区域被排除在外。表层和深层视网膜毛细血管丛 (SCP) 的血管密度 (VD) 和血管长度密度 (VLD) DCP) 和 CC 流量赤字 (FD) 被分析、量化并在不同组之间进行比较。结果 高度近视25例25眼、中度近视25例25眼、正常年龄匹配对照25眼25眼纳入研究。与正视对照组相比，高度近视组 SCP 的 VD 较低（p < 0.05），但 DCP 的 VD 在三组之间没有显着差异（p > 0.05）。高度近视组和中度近视组SCP的VLD低于对照组（p < 0.05），而高度近视组DCP的VLD低于中度近视和正视对照组（p < 0.05） 0.05）。高度近视组的 CC FD% 显着大于对照和中度近视受试者 (p < 0.05)。值得注意的是，CC 血流不足的严重程度与脉络膜厚度无关（p > 0.05）。结论 视网膜微血管系统可能表现出高度近视眼的改变。与低度近视眼相比，高度近视眼的黄斑区 CC 显示出更大的损伤，并且这些缺陷在没有病理性或退行性近视特征的情况下已经存在。CC FD 导致近视性黄斑病变的阈值仍有待确定。与低度近视眼相比，高度近视眼的黄斑区 CC 显示出更大的损伤，并且这些缺陷在没有病理性或退行性近视特征的情况下已经存在。CC FD 导致近视性黄斑病变的阈值仍有待确定。与低度近视眼相比，高度近视眼的黄斑区 CC 显示出更大的损伤，并且这些缺陷在没有病理性或退行性近视特征的情况下已经存在。CC FD 导致近视性黄斑病变的阈值仍有待确定。