Objective: To compare the difference and agreement of corneal refractive power and astigmatism measured by the new swept-source anterior segment optical coherence tomography (SS-AS-OCT) device (CASIA2) and Scheimpflug imaging device (Pentacam) in age-related cataract patients. Methods: In this cross-sectional study, 112 eyes of 112 patients with age-related cataract were examined before phacoemulsification in the Tianjin Medical University Eye Hospital from April to May 2020. The steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), degree and axis of astigmatism of the corneal anterior and posterior surfaces and the total cornea were recorded. The difference in astigmatism was analyzed by the arithmetic method and the vector method. The difference of data was evaluated using Paired t test or Wilcoxon test. The agreement of data was evaluated using Bland-Altman plots. Results: The patients were 44 males and 68 females with an average age of (67±10) years. There were no statistically differences in the Ks and Km values of the corneal anterior surface between the Pentacam and the CASIA2 (both P>0.05). There was significant difference in the Kf values of the corneal anterior surface between the Pentacam and the CASIA2 [(44.24±1.73) D vs. (44.14±1.64) D; t=2.278; P<0.05]. The Ks, Kf, and Km values of the posterior surface of the cornea measured by the Pentacam and the CASIA2 were (-6.60±0.29) D vs. (-6.45±0.28) D, (-6.34±0.27) D vs. (-6.17±0.25) D, and (-6.47±0.26) D vs. (-6.31±0.25) D, respectively. The Ks, Kf, and Km values of the total cornea measured by the two instruments were (45.08±1.84) D vs. (43.94±1.64) D, (44.18±1.85) D vs. (43.02±1.64) D, and (44.63±1.82) D vs. (43.48±1.60) D, respectively. There were significant differences in the Ks, Kf, and Km values of the posterior surface of the cornea and the total cornea (t=-14.440, -13.522, -17.186, 21.016, 21.819, 22.981; all P<0.01). The degree and axis of astigmatism of the corneal anterior and posterior surfaces and the total cornea showed no statistically significant difference (all P>0.05). Vector operation results showed that the astigmatism difference vector (DV) of the Pentacam and the CASIA2 on the anterior surface of the cornea was 0.06 D@57°±0.64 D,>0.50 D in 47 eyes (41.96%). The astigmatism DV on the posterior surface of the cornea was 0.07 D@174°±0.21 D, >0.50 D in 2 eyes (1.79%). The astigmatism DV on the total cornea was 0.13 D@3°±0.69 D,>0.50 D in 59 eyes (52.68%). The results of the two devices were positively correlated (r values of the Ks, Kf, Km, and astigmatism degree on the anterior surface of the cornea were 0.970, 0.968, 0.976, and 0.697, respectively, on the posterior surface of the cornea were 0.918, 0.875, 0.925, and 0.517, respectively, and on the total cornea were 0.951, 0.955, 0.959, and 0.622, respectively; all P<0.01). Bland-Altman analysis showed that the Ks, Kf, Km, and astigmatism degree of the corneal anterior and posterior surfaces measured by the two devices were consistent, with 2.68% to 8.04% of the measured values outside 95% limits of agreement (95%LoA). The 95%LoA of the total corneal Ks, Kf, and Km between the two devices was 0.01 to 2.28 D, 0.06 to 2.27 D, and 0.10 to 2.20 D, respectively, with a wide 95%LoA range and poor consistency. Conclusions: The corneal refractive power and astigmatism measured by the CASIA2 and the Pentacam shows little difference on the anterior surface of the cornea, with good agreement. However, the refractive power results of the posterior surface of the cornea and the total cornea show great difference, suggesting that these two instruments cannot be used interchangeably in clinical practice. (Chin J Ophthalmol, 2021, 57: 48-55).
目的： 比较新型扫频源眼前节相干光层析成像仪CASIA2与Scheimpflug眼前节分析仪Pentacam测量年龄相关性白内障患者角膜屈光力、角膜散光的差异性和一致性。 方法： 横断面研究。收集2020年4至5月在天津医科大学眼科医院白内障科拟行超声乳化白内障吸除联合人工晶状体植入术的年龄相关性白内障患者共112例（112只眼），分别采用Pentacam和CASIA2测量角膜前后表面及全角膜的陡峭轴、平坦轴及平均角膜屈光力、散光度数及散光轴向，采用算术法和矢量法分析散光的差异。采用配对样本t检验或Wilcoxon符号秩检验进行两组测量结果间差异性分析，一致性评价采用Bland-Ahman分析。 结果： 112例（112只眼）患者中，男性44例，女性68例，年龄（67±10）岁。Pentacam与CASIA2测量的角膜前表面陡峭轴及平均角膜屈光力差异均无统计学意义（均P>0.05）；测量的平坦轴角膜屈光力分别为（44.24±1.73）、（44.14±1.64）D，差异有统计学意义（t=2.278；P<0.05）。Pentacam测量的角膜后表面陡峭轴、平坦轴及平均角膜屈光力分别为（-6.60±0.29）、（-6.34±0.27）、（-6.47±0.26）D，CASIA2测量的角膜后表面陡峭轴、平坦轴及平均角膜屈光力分别为（-6.45±0.28）、（-6.17±0.25）、（-6.31±0.25）D，二者差异均有统计学意义（t=-14.440，-13.522，-17.186，均P<0.01）。Pentacam测量的全角膜陡峭轴、平坦轴及平均角膜屈光力分别为（45.08±1.84）、（44.18±1.85）、（44.63±1.82）D，CASIA2测量的全角膜陡峭轴、平坦轴及平均角膜屈光力分别为（43.94±1.64）、（43.02±1.64）、（43.48±1.60）D，二者差异均有统计学意义（t=21.016，21.819，22.981；均P<0.01）。两设备散光度数及散光轴向的测量结果差异均无统计学意义（均P>0.05）。矢量运算结果显示，Pentacam与CASIA2测量角膜前表面散光差异矢量质心为0.06 D@57°±0.64 D，其中47只眼（41.96%）>0.50 D；角膜后表面散光差异矢量质心为0.07 D@174°±0.21 D，其中2只眼（1.79%）>0.50 D；全角膜散光差异矢量质心为0.13 D@3°±0.69 D，其中59只眼（52.68%）>0.50 D。相关性分析显示，两设备测量结果均呈正相关，角膜前表面陡峭轴、平坦轴、平均角膜屈光力及散光度数的r值分别为0.970，0.968，0.976，0.697；角膜后表面陡峭轴、平坦轴、平均角膜屈光力及散光度数的r值分别为0.918，0.875，0.925，0.517；全角膜陡峭轴、平坦轴、平均角膜屈光力及散光度数的r值分别为0.951，0.955，0.959，0.622（均P<0.01）。Bland-Altman分析显示，两设备测量角膜前、后表面陡峭轴、平坦轴、平均角膜屈光力及散光度数均有较好的一致性，2.68%~8.04%的测量差值在95%一致性界限（95%LoA）外；两设备测量全角膜陡峭轴、平坦轴及平均角膜屈光力的95%LoA范围分别为0.01~2.28、0.06~2.27、0.10~2.20 D，95%LoA范围较宽，一致性较差。 结论： CASIA2与Pentacam测量年龄相关性白内障患者角膜屈光力及散光，在角膜前表面差异性较小，一致性较好，但角膜后表面及全角膜屈光力测量结果差异性较大，临床上不建议互换。（中华眼科杂志，2021，57：48-55）.
Keywords: Age factors; Astigmatism; Cataract; Corneal refractive power; Corneal topography; Tomography, optical coherence.