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

<b>Purpose</b>: 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. <b>Methods</b>: 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. <b>Results</b>: 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). <b>Conclusions</b>: 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：明确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（包括瘢痕尺寸、瘢痕深度及角膜厚度）中的重复性与复现性。
研究方法：召回印度南部某三级眼科中心内，于真菌性角膜炎治愈后两年的随访患者。对存在角膜瘢痕的患眼，由两名对彼此检查结果设盲的眼科医师完成裂隙灯检查。针对AS-OCT与Scheimpflug摄影，由一名技师为每只患眼完成两次扫描，另一名技师再完成第三次扫描。随后由三名对彼此评估结果设盲的评分者从AS-OCT图像中完成瘢痕尺寸测量。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），以评估各项测量的重复性与复现性。
研究结果：共计50只患眼完成全部测量项目。以两条最长垂直径线的几何均值作为瘢痕尺寸的量化指标，其取值范围为0.8至5.4（平均值2.8mm，95%置信区间2.6至3.1）。当通过AS-OCT图像勾画瘢痕边界时，两名不同操作者的瘢痕尺寸测量结果复现性最优（ICC=0.90，95%置信区间0.86至0.94），而通过裂隙灯检查进行评估时，其复现性最差（ICC=0.80，95%置信区间0.70至0.90）。
研究结论：针对角膜瘢痕的AS-OCT与Scheimpflug成像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。