超长扫描深度的频域光学相干断层扫描在小鼠眼球生物学测量中的应用

摘要

目的 利用自行搭建的超长扫描深度的频域光学相干断层扫描(SD-OCT)活体测量小鼠眼球的眼轴长度、曲率等各眼内生物学参数,并评估其重复性和再现性.方法 实验研究.本研究自主研发的超长扫描深度SD-OCT扫描深度7.3 mm(空气中),系统轴向扫描(A-Scan)速度28 kHz,轴向分辨率7.5 μm,横向分辨率19 μm.共有5只40日龄的C57BL/6小鼠(10眼)经历2天次的测量.第1天,由操作者1先执行测量步骤,连续拍摄2幅图后,由操作者2紧接着拍摄1幅图.在3次拍摄中,每次都保证前后拍摄的时间耽搁小于5 min.2d以后,所有的小鼠再由操作者1拍摄1幅图,随后每只小鼠再进行1次时域OCT(TD-OCT)拍摄.所有测量都在下午2:00到4:00之间进行.测量的重复性和再现性评估都采用重复性系数、组内相关系数ICCs、Wilcoxon配对测试及绘制Bland-Altman图来综合分析.SD-OCT和TD-OCT的测量结果比较采用独立样本t检验.结果 用SD-OCT成功获得了清晰、高质量的小鼠眼球一次性成像.除角膜、前房外,其他数据接近于TD-OCT.前房、晶状体、玻璃体和眼轴的重复性/再现性系数均小于3％且对应的组内相关系数(ICCs)几乎都大于0.75,角膜和视网膜的重复性/再现性系数小于5％且对应的ICCs相对较小.除操作者1第1天获取的2组角膜数据之间差异有统计学意义外(Z=-2.310,P＜0.05),其余差异均无统计学意义.眼轴等生物学参数的Bland-Altman分析图显示所有的数据点都分布在95％可信区间内.各个曲率的重复性/再现性系数均小于5％.角膜前表面曲率半径和晶状体前、后表面曲率半径的ICCs基本大于0.75,而角膜后表面曲率半径的ICC大于0,45.Bland-Altman图显示曲率再现性的数据点约有5％分布在95％可信区间外.结论 利用SD-OCT,可获得高清晰的从小鼠角膜到视网膜的横断面切片图像,不仅能计算传统的眼轴等轴向生物学参数的长度,而且还能计算眼内各个成分的曲率半径,具有较好的重复性和再现性.%Objective To assess the accuracy,precision,repeatability,and reproducibility of biometric measurement of the mouse eye made by extended scan depth spectral domain optical coherence tomography (SD-OCT).Methods It was an experimental study.An SD-OCT with an extended depth range of 7.3 mm,A-scan speed of 28 kHz,axial resolution of 9.0 μm and transversally 19 μm was developed.Five 40-day-old C57BL/6 mice (10 eyes) were imaged with a custom built,extended scan depth SD-OCT in 2 sessions.Two scans were performed by operator 1 and a following scan by operator 2 at the first session,to determine repeatability and interoperator reproducibility.Intersession reproducibility was assessed by an additional scan performed by operator 1 2 days later.The data were compared to those from time-domain OCT (TD-OCT) by independent t test.All experiments were performed between 2:00 PM and 4:00 PM.The repeatability and reproducibility were evaluated by coefficient of repeatability/reproducibility,intraclass correlation coefficients (ICCs),Wilcoxon matched-pairs test and Bland-Altman graph.Results High-quality OCT images of the entire mouse eyes with high resolution were acquired.The ocular dimensions from TD-OCT measurements were close to these obtained by SD-OCT.The overall coefficients of repeatability/reproducibility for anterior chamber depth,lens thickness,vitreous chamber and axial length were all less than 3％ and relevant intraclass correlation coefficients (ICCs) were nearly greater than 0.75,whereas these were less than 5％ and ICCs were smaller for corneal thickness and retinal thickness.Wilcoxon analysis showed there was no statistically significant difference between any 2 groups for all parametres except corneal thickness of repeatability (Z=-2.310,P＜0.05).From the graph of differences against mean for the axial lengths,it can be seen that 100％ of the values fall within 2 SDs of the mean.The overall coefficients of repeatability/reproducibility for curvatures were less than 5％.The ICCs for anterior curvature of the cornea and anterior/posterior curvatures of the lens were almost greater than 0.75,while it was greater than 0.45 for posterior curvature of the cornea.Graph of differences against means of average curvatures of reproducibility showed 5％ data were without 2 SDs of the mean.Conclusion SD-OCT is quite repeatable and reproducible for ocular dimension measurement of mouse eye.The novel method is helpful for monitoring the growth of the eye in normal mice and in strains that have developmental conditions such as myopia.