IOL CALCULATION IN HIGHLY MYOPIC PATIENTS

Background: To determine the accuracy of the T2 formula as applied to highly myopic eyes, to compare the T2 formula to the SRK/T and Holladay 1 formulas, and to describe possible improvements for estimating corneal height and prediction error in two settings, the Hadassah Hospital, Ophthalmology Department, Jerusalem, Israel and Clínica Barraquer, Bogotá, Colombia. Methods: In this retrospective case series , optical biometer measurements were taken for 63 highly myopic patients (spherical power ≤ 5 D) undergoing uneventful crystalline lens phacoemulsification and insertion of an acrylic intraocular lens. Prediction errors were obtained, with estimations of ± 0.50 D, ± 1.00 D, and greater than ± 2.00 D. Methods to improve corneal height calculations are described. Results: The SRK/T (mean absolute error [MAE] = 0.418; median absolute error [MedAE] = 0.352) formula was the most accurate, followed by the T2 (MAE = 0.435; MedAE = 0.381) and Holladay 1 (MAE = 0.455; MedAE = 0.389) formulas. Both the SRK/T and T2 formulas overestimated corneal height, but values were higher with the T2 formula. Corneal height was more precisely estimated using an alternative method that, when combined with axial length optimization, resulted in lower MAE (0.425) and MedAE (0.365) values than when applying the T2 formula alone. Conclusions: The T2 formula seems to be less accurate than the SRK/T formula in highly myopic eyes. Improvements in corneal height estimations may result in better intraocular lens estimations. Key words: T2 formula, high myopia, corneal height estimation, cataract surgery, intraocular lens calculation .研究背景：本研究旨在明确T2公式在高度近视眼人群中的应用准确性，并将T2公式与SRK/T、Holladay 1公式进行对比；同时针对两处临床场景——以色列耶路撒冷哈达萨医院眼科与哥伦比亚波哥大的巴拉克尔眼科诊所，探讨估算角膜高度及预测误差的潜在优化方案。 研究方法：本研究为回顾性病例系列研究，纳入63例球镜度数≤5屈光度的高度近视患者，所有患者均接受了无并发症的晶状体超声乳化术并植入丙烯酸酯人工晶状体，对其行光学生物测量仪检测。统计得到预测误差，并按±0.50屈光度、±1.00屈光度及＞±2.00屈光度进行分层评估，同时详述了优化角膜高度计算的相关方法。 研究结果：SRK/T公式的预测准确性最优，其平均绝对误差（mean absolute error, MAE）为0.418，中位数绝对误差（median absolute error, MedAE）为0.352；其次为T2公式（MAE=0.435，MedAE=0.381）与Holladay 1公式（MAE=0.455，MedAE=0.389）。SRK/T与T2公式均存在角膜高度高估的情况，且T2公式的高估程度更高。采用改良方法估算角膜高度时，其准确性更优；若将该方法与眼轴长度优化方案结合，相较于单独使用T2公式，可获得更低的MAE（0.425）与MedAE（0.365）。 研究结论：在高度近视眼人群中，T2公式的预测准确性似乎低于SRK/T公式。优化角膜高度估算方法，或可提升人工晶状体度数计算的准确性。 关键词：T2公式，高度近视，角膜高度估算，白内障手术，人工晶状体度数计算