基于新型扫频光源生物测量仪测量的全角膜屈光力和传统角膜屈光力计算IOL度数的准确性比较

目的：比较基于新型扫频光源生物测量仪测量的全角膜屈光力（TK）和传统角膜屈光力（K）计算人工晶状体（IOL）度数的准确性。方法：前瞻性自身对照研究。收集2021年5—11月在北京大学人民医院眼科因双眼年龄相关性白内障行白内障超声乳化联合衍射型三焦点IOL植入术的患者29例（58 眼）。使用IOLMaster 700扫频光学生物测量仪进行术前眼轴长度、前房深度、中央角膜厚度、晶状体厚度、前后表面角膜屈光力、TK、白到白角膜直径的测量。分别使用K和TK按照目前常用IOL度数计算公式（SRK/T、Haigis、Holladay2及Barrett Universal Ⅱ）及额外新增加的Barrett TK Universal Ⅱ公式计算IOL度数及预测屈光度数。术后1、3个月进行最佳矫正远视力检查及主觉验光。计算绝对预测误差、绝对预测误差均值、绝对预测误差中位数（MedAE）及各个公式预测误差值在±0.25、±0.50、±0.75、±1.00D内所占的百分比。采用Wilcoxon符号秩和检验和McNemar's卡方检验进行数据分析。结果：TK值和K值的差异平均值（TK-K）为0.007D，二者之间的组内相关系数为0.996 （P<0.001），提示二者之间有良好的一致性。在Haigis和Barrett Universal Ⅱ公式，使用TK值计算的MedAE略小于K值计算的MedAE；在SRK/T和Holladay2公式，使用K值计算的MedAE略小于TK值计算的MedAE。Barrett TK Universal Ⅱ比Barrett Universal Ⅱ公式预测误差值在±0.25、±0.50D内所占的百分比略高，而SRK/T、Haigis及Holladay2公式K值计算比TK值计算预测误差值在±0.25、±0.50D内所占的百分比略高，差异均没有统计学意义。结论：基于新型扫频光源生物测量仪测量的TK值在不同IOL度数计算公式中的IOL度数计算的准确性与K值一致，利用TK值在Barrett TK Universal Ⅱ公式的计算准确性更高。

Comparison of the Accuracy of Total Keratometry and Conventional Keratometry for IOL Power Calculation Based on the New Swept-Source Optical Coherence Tomography Biometry

Objective: To compare the accuracy of total keratometry (TK) and conventional keratometry (K) for intraocular lens (IOL) power calculation based on the new swept-source optical coherence tomography biometry. Methods: This was a prospective self controlled study, 29 patients (58 eyes) with binocular age-related cataract were enrolled for the phacoemulsification combined with diffractive trifocal IOL implantation during May 2021 and November 2021 in Peking University People's Hospital. Eyes were assessed using a swept-source optical biometer (IOLMaster 700). Axial length, anterior chamber depth, central corneal thickness, lens thickness, posterior keratometry, TK, and white-to-white corneal diameter were recorded. Emmetropic IOL power was calculated using K and TK in the current standard formulas (SRK/T, Haigis, Holladay2, and Barrett Universal II) and a new formula developed for TK (Barrett TK Universal II). Selected IOL power and predicted refractive outcomes were recorded. Corrected distance visual acuity and postoperative manifest refraction were measured 1 month and 3 months postoperatively. The absolute prediction error, mean absolute error, median absolute error (MedAE), and the percentages of eyes within prediction errors of ±0.25 D, ±0.50 D, ±0.75 D, and ±1.00 D were calculated for all IOL formulas. Wilcoxon signed-rank tests and McNemar's tests were used to analyze the difference. Results: There was strong agreement between K and TK (intraclass correlation coefficient=0.996), with a mean difference of 0.007 D. A relatively lower MedAE values were observed for Haigis and Barrett Universal Ⅱ for TK when compared with K. MedAE from TK was a trend toward larger than that from K in SRK/ T and Holladay2 formulas. A relatively greater proportion of eyes fell within ±0.25 D and ±0.50 D of the predicted postoperative spherical equivalent range in the TK group than in the K group for Barrett Universal Ⅱ formula. Proportion of eyes within ±0.25 D and ±0.50 D of predicted refraction were slightly higher in the K group for SRK/T, Haigis and Holladay2. However, differences in MedAEs, and percentages of eyes within the above prediction errors were not statistically significant. Conclusions: Conventional K and TK for IOL calculation showed strong agreement for refractive prediction for IOL power calculation based on IOLMaster 700, and with a trend toward better refractive outcomes using TK for Barrett Universal Ⅱ formula.