基于全角膜屈光力计算角膜异常B/F值的白内障患者人工晶状体屈光力

目的：研究基于全角膜屈光力（TCRP）的人工晶状体（IOL）屈光力计算公式，计算异常角膜后前曲率半径比（B/F）值的白内障患者IOL屈光力的精确性。方法：前瞻性临床研究。连续选取角膜异常 B/F值的白内障患者51例（51眼）。高B/F值组：B/F值≥85%，24例（24眼），B/Fratio为（86.2±0.5）%； 低B/F值组：B/F值≤78%，27例（27眼），B/F值为（76.6±0.6）%。使用TCRP Method计算，角膜屈光力采用Pentacam中央3 mm、瞳孔中心、区域的TCRP，采用IOLMaster 500的眼轴长度和前房深度。术后3个月行裸眼视力（UCVA，logMAR）、电脑验光检查。所有患者、高B/F值组、低B/F值组这3组，组内TCRP Method、Higis、Hoffer-Q、SRK-T、Hollady-Ⅰ公式的绝对预测误差（APE）总体比较采用非参数检验中的Friedman检验法。各组中TCRP Method的APE分别与Haigis、Hoffer-Q、 SRK-T、Holladay-Ⅰ进行两两比较，采用Wilcoxon符号秩和检验。结果：术后3个月UCVA：高B/F值组为0.19±0.09，低B/F值组为0.19±0.08，2组间差异无统计学意义（t=0.787，P=0.435）。术后3个月的平均绝对误差（MAE）：高B/F值组为（0.38±0.16）D，低B/F值组为（0.42±0.19）D。所有术眼术后3个月按照TCRP Method、Higis、Hoffer-Q、SRK-T、Hollady-Ⅰ公式计算的MAE分别为（0.40±0.17） D、（0.64±0.25）D、（0.73±0.27）D、（0.98±0.32）D、（0.84±0.25）D，5种公式的APE总体比较差异有统计学意义（χ2 =12.47，P=0.023）。进一步将TCRP Method的APE与Haigis、Hoffer-Q、SRK-T、 Holladay-Ⅰ公式两两比较，差异均有统计学意义（Z=2.97、3.53、4.01、3.75，均P<0.05）。高B/F值组和低B/F值组：5种公式的APE总体比较，差异均有统计学意义（χ2 =12.35、13.21，均P<0.05）。结论：对于角膜异常B/F值的白内障患者，使用常规公式计算IOL屈光力的精确性较差，使用基于TCRP的IOL屈光力计算公式精确性高，术后视力佳。

Calculation of Intraocular Lens Power in Cataract Patients with an Abnormal B/F Ratio based on Total Corneal Refractive Power

Objective: To research the accuracy of an intraocular lens (IOL) refractive power calculation formula based on total corneal refractive power (TCRP) in calculating the IOL refractive power in cataract patients with an abnormal B/F ratio. Methods: This was a prospective clinically controlled study. Fifty-one cataract patients (51 eyes) with an abnormal corneal B/F ratio were selected consecutively. Patients were divided into two groups: A high B/F ratio group, B/F≥85%, 24 patients (24 eyes), mean=86.2±0.5%; alow B/F ratio group, B/F≤78%, 27 patients (27 eyes), mean=76.6±0.6%. The TCRP measured by the Pentacam (3 mm, pupil center, zone), the axial length (AL) and anterior chamber depth (ACD) measured by the IOL-Master 500 were used in the self-developed IOL refractive power calculation formula. Uncorrected distance visual acuity (logMaR) and optometric testing with a computer were performed 3 months after surgery. Results: The uncorrected distance visual acuity (UCDVA) at 3 months after surgery was 0.19±0.09 in the high B/F ratio group and 0.19±0.08 in the low B/F ratio group. There was no significant difference between the two groups (t=0.787, P=0.435). The mean absolute error (MAE) at 3 months after surgery was 0.38±0.16 D in the high B/F ratio group and 0.42±0.19 D in the low B/F ratio group. Three months after surgery, the MAEs of all patients calculated by the TCRP Method, Higis, HofferQ, SRK-T, and Hollady-Ⅰ formulas were 0.40±0.17 D, 0.64±0.25 D, 0.73±0.27 D, 0.98±0.32 D and 0.84±0.25 D, respectively. The differences in the absolute prediction error (APE) of the five formulas were statistically significant (χ2 =12.47, P=0.023). Furthermore, the APE of the TCRP Method was compared with the Haigis, Hoffer-Q, SRK-T, and Holladay-Ⅰ formulas, and the differences were statistically significant (Z=2.97, 3.53, 4.01, 3.75, all P<0.05). The overall comparisons of the five formulas of the APE were statistically significant for the high B/F ratio group and low B/F ratio group: (χ2 =12.35, P=0.037; χ2 =13.21, P=0.025). Conclusions: For cataract patients with an abnormal B/F ratio, the accuracy of the conventional IOL refractive power calculation formula is poor, and the TCRP-based IOL refractive power calculation formula has high accuracy and perfect UCDVA.