Repeatability and Reproducibility of Slit Lamp, Optical Coherence Tomography, and Scheimpflug Measurements of Corneal Scars

Purpose: To determine the repeatability and reproducibility of anterior segment optical coherence tomography (AS-OCT) and Scheimpflug photography for several measurements of corneal scars, including scar size, scar depth, and corneal thickness. Methods: A series of patients treated for fungal keratitis at a tertiary eye care center in South India were recalled two years after successful treatment. Eyes with corneal scars had a slit lamp examination performed by two ophthalmologists masked to the other’s examination. For AS-OCT and Scheimpflug photography, each eye had two scans taken by one technician and a third scan taken by a separate technician. Scar measurements were subsequently assessed from AS-OCT images by three graders masked to each other’s results. Repeatability and reproducibility were assessed by calculating the intra-class correlation coefficient (ICC) from mixed effects linear regression models. Results: Fifty eyes had all measurements taken. The corneal scar size, measured as the geometric mean of the two longest perpendicular meridians, ranged from 0.8 to 5.4 (mean 2.8 mm, 95%CI 2.6 to 3.1). Scar size measurements taken by two separate individuals were most reproducible when the border of the scar was traced from the OCT (ICC 0.90, 95%CI 0.86 to 0.94), and least repeatable when assessed from slit lamp examination (ICC 0.80, 95%CI 0.70 to 0.90). Conclusions: AS-OCT and Scheimpflug imaging of corneal scars produced measurements with acceptable reproducibility that could be useful as cornea-specific outcomes for clinical trials.研究目的：评估眼前节光学相干断层扫描（anterior segment optical coherence tomography, AS-OCT）与Scheimpflug摄影在角膜瘢痕多项测量指标（包括瘢痕面积、瘢痕深度及角膜厚度）中的重复性与复现性。 研究方法：招募印度南部某三级眼科中心确诊真菌性角膜炎并接受成功治疗的患者，于治疗完成两年后进行回访。存在角膜瘢痕的患眼由两名对彼此检查结果不知情的眼科医师开展裂隙灯检查。针对眼前节光学相干断层扫描与Scheimpflug摄影，由一名技师对每只患眼采集两次扫描图像，另一名技师再采集一次扫描图像。随后由三名对彼此评估结果不知情的阅片者从眼前节光学相干断层扫描图像中完成瘢痕各项测量指标的评估。重复性与复现性通过混合效应线性回归模型计算组内相关系数（intra-class correlation coefficient, ICC）进行分析。 研究结果：本研究共纳入50只完成全部测量指标采集的患眼。以两条最长垂直径线的几何均值作为瘢痕面积的量化指标，其取值范围为0.8至5.4（平均2.8 mm，95%置信区间2.6至3.1）。当通过光学相干断层扫描图像勾画瘢痕边界时，两名独立操作者的瘢痕面积测量结果复现性最佳（组内相关系数0.90，95%置信区间0.86至0.94），而通过裂隙灯检查完成评估时的重复性最差（组内相关系数0.80，95%置信区间0.70至0.90）。 研究结论：针对角膜瘢痕的眼前节光学相干断层扫描与Scheimpflug成像所获得的测量结果具有可接受的复现性，可作为角膜特异性结局指标应用于临床试验。