扫描信号强度对OCTA测量正常人黄斑浅层血流的影响

目的：研究扫描信号强度（SS）对光学相干断层扫描血管成像（OCTA）测量正常人黄斑浅层血流密度的影响。方法：系列病例研究。对2020年9─12月在北京同仁医院进行健康体检的某事业单位在职职工进行系统眼科检查，应用光学相干断层扫描（OCT）和OCTA测量平均黄斑节细胞内丛状层 （mGCIPL）厚度和黄斑6 mm×6 mm浅层血流密度。提取血流密度（VD）、灌注密度（PD）和黄斑中心凹无血管区（FAZ）等参数。纳入SS为8、9、10的患者，并分为SS8组、SS9组和SS10组。取右眼数据用于统计学分析。采用方差分析和非参数检验分析比较3组间VD、PD和FAZ参数之间的差别。采用 Spearman检验分析黄斑VD和PD之间的相关关系。采用多元线性回归分析SS、年龄、性别、等效球镜度（SE）以及mGCIPL厚度对黄斑浅层血流的影响。结果：75例（75眼）健康人纳入研究，其中SS8 组20眼，SS9组20眼，SS10组35眼。黄斑总体VD在SS8、SS9和SS10之间差异有统计学意义（Hc=19.86， P<0.001）。黄斑总体PD在SS8、SS9和SS10之间差异有统计学意义（Hc=25.51，P<0.001）。3组间FAZ 参数差异无统计学意义。Spearman分析显示黄斑总体VD和总体PD呈正相关（r=0.978，P<0.001）。多 元线性回归分析显示平均mGCIPL厚度值每减少1 μm，总体VD减少0.05 mm-1，总体PD减少0.002； SS每减少1个单位，总体VD减少0.55 mm-1，总体PD减少0.02。年龄、性别和SE对VD和PD无影响。 结论：在SS为8以上的扫描中，正常人黄斑FAZ血流参数无明显差别，但是在黄斑VD和PD不同信号强度存在明显差异。在解读旁中心凹区域血流参数时需要考虑信号强度差别带来的影响。

Effect of Signal Strength in the Analysis of Normal Macular Microvascular Density Using Optical Coherence Tomography Angiography

Objective: To report the effects of signal strength (SS) on the normal macular microvascular density acquired from optical coherence tomography angiography (OCTA). Methods: This was a case series study. Normal subjects (right eyes) were recruited from September 2020 to December 2020 in the Beijing Tongren Hospital. All subjects underwent 6 mm×6 mm high-definition (HD)-OCT/OCTA. Macular ganglioncell-inner plexiform layer (mGCIPL) thickness and macular microvascular density were analyzed using the Cirrus OCTA system (Angio Plexversion 10.0). Subjects were grouped according to the signal strength (SS) (8, 9, 10): SS8, SS9 and SS10. Vessel density (VD), perfusion density (PD) and foveal avascular zone (FAZ) parameters of the superficial capillary plexus were calculated. One-way analysis of variance and a nonparametric test were conducted to compare macular VD, PD and FAZ among the three groups. Spearman correlation was used to determine the relationship between macular VD and PD. Multiple regression analysis determined the association between macular vascular parameters and SS, age, gender, spherical equivalent (SE) and mGCIPL thickness. Results: Seventy-five subjects (75 eyes) were included. SS8 group was 20 eyes, SS9 group was 20 eyes and SS10 group was 35 eyes. There were significant differences between SS8, SS9 and SS10 (Hc=19.86, P<0.001). There were significant differences between the SS8, SS9 and SS10 groups in the total area of the macular PD (Hc=25.51, P<0.001). There were no significant differences among the three groups in FAZ parameters. The Spearman test showed that the total area of VD was significantly correlated with PD (r=0.978, P<0.001). The total area of VD was associated with mGCIPL and SS; the total area of PD was associated with mGCIPL and SS. Both VD and PD were not associated with age, gender or SE. Conclusions: In normal subjects, macular VD and PD show significant differences in different SS groups, but the FAZ parameters show no significant differences among the SS groups above 8. This may suggest the impact of SS should be considered carefully when interpreting perifoveal vessel parameters.