[Comparison of formulas for intraocular lens power calculation after corneal refractive surgery].

Objective: To evaluate the accuracy of five intraocular lens (IOL) power calculation formulas for calculating IOL power in patients with previous myopia-corrected corneal refractive surgery. Methods: In this case series study, a total of 30 eyes of 30 patients who had excimer laser corneal refractive surgery for myopia and subsequent cataract surgery in Qingdao Eye Hospital from April 2020 to October 2022 were included. The Pentacam anterior segment analysis system and IOLMaster were used to measure ocular parameters, including axial length, anterior chamber depth, keratometry, lens thickness, and mean true net power (mTNP). Five formulas were used for IOL power calculation: Shammas formula, Olsen formula, SRK/T (mTNP) formula, Haigis-L formula, and Barrett True-K formula. After cataract extraction, we obtained the actual postoperative refraction by measuring the objective refraction. The prediction error was determined as the difference between the actual postoperative refraction and the predicted refraction, and the absolute value of the prediction error was the absolute error. The differences in the calculation errors of the 5 formulas were compared. Results: Regarding the prediction errors, the results of the SRK/T (mTNP) and Olsen formulas were better than those of Shammas and Haigis-L, and the differences were statistically significant (all P<0.05). The proportion of eyes with an absolute error of 0.50 D for Barrett True-K was highest (70%, 21/30), followed by the SRK/T (mTNP) formula (67%, 20/30). The proportions of eyes with an absolute error within 1.00 D for Barrett True-K, SRK/T (mTNP), and Olsen were all over 80%, with 24 eyes, 24 eyes, and 25 eyes, respectively. Conclusions: The Barrett True-K formula showed high accuracy in predicting the refraction after cataract extraction in patients with a history of corneal refractive surgery for myopia. The calculation result of the Haigis-L formula was highly unstable.目的： 评价5种人工晶状体（IOL）度数计算公式在无病史资料的角膜屈光手术矫正近视的患者中对于IOL度数计算中的准确性。 方法： 病例系列研究。收集2020年4月至2022年10月就诊于山东第一医科大学附属青岛眼科医院，既往有近视矫正准分子激光角膜屈光手术病史的白内障手术患者30例（30只眼）。采用Pentacam眼前节分析系统、IOL Master生物测量仪等仪器测量眼轴长度、前房深度、角膜曲率、晶状体厚度、平均真实净角膜屈光力（mTNP）等眼部参数。分别采用Shammas公式、Olsen公式、SRK/T（mTNP）公式、Haigis-L公式及Barrett True-K公式进行IOL度数计算后选择合适的IOL度数。白内障摘除手术后进行客观验光获取术眼实际屈光度数，以实际屈光状态与预测屈光度数之间的差异为预测误差，再取绝对值得到绝对误差，比较5种公式计算结果误差的差异。 结果： 比较5种公式的预测误差发现，SRK/T（mTNP）、Olsen公式的结果均优于Shammas公式和Haigis-L公式，差异有统计学意义（均P<0.05）。Barrett True-K公式的绝对误差<0.50 D的眼占比最高（70%，21/30），其次是SRK/T（mTNP）公式（67%，20/30），Barrett True-K公式、SRK/T公式及Olsen公式的绝对误差<1.00 D的眼占比均>80%，分别为24、24及25只眼。 结论： Barrett True-K公式预测角膜屈光手术矫正近视的患者白内障摘除术后屈光度数表现出较高的准确性；Haigis-L公式的计算结果不稳定性较高。.