Clinical Study Of The Different Calculation Formulas Selection For Intraocular Lens For High Myopia With Cataract

Objective: To observe the accuracy of using three different intraocular lens calculation formulas to predict postoperative diopter for cataract patients with high myopia,and to provide evidence for doctors in basic hospitals to choose more suitable intraocular lens calculation formula and reserve postoperative diopter for cataract patients with high myopia under limited conditions.Methods: In this study,65 cases(105 eyes)of high myopia complicated with cataract were selected from March 2018 to May 2021.They had complete preoperative examination data and postoperative follow-up data.According to different axil length(AL),they were divided into:group A: 26≤AL≤28 mm,group B:28<AL≤30 mm and group C:AL>30 mm,and according to the average corneal refractive power,they were was divided into: group a: K <40D,group b:40≤K≤42 D,group c: 42<K≤45 D and group d:K>45 D.IOLMaster500 was used to measure the ocular biological data such as AL,corneal refractive power and anterior chamber depth(ACD)before operation,and intraocular lens with suitable reserved diopter was implanted according to the patient’s condition.Put the intraocular lens degree into the three kinds of intraocular lens power calculation formulas(SRK-T,Haigis formular and Barrett Universal Ⅱ formula provided by Alcon company),obtained the each formula reserve postoperative refractive outcome in theory.The patients were followed up after 3 months postoperatively while the refractive status was stable,and the actual postoperative refractive outcome was measured for each patient.Comparing and analyzing the absolute value of difference between preoperative theoretical reserved diopter and postoperative actual diopter of three different formulas betweeen different axial length and different corneal refractive power,that is mean absolute refractive error(MAE),and evaluating the accuracy of the three different formulas in cataract patients with high myopia objectively.Results: With the increase of axial length of the eyes with high myopia,the MAE of each formula increased gradually(P<0.05).The MAE of the three formulas were statistically different in the groups with the group B 28<AL≤30 mm and group C AL>30 mm(P<0.05),but not in the group with the group A 26≤AL≤28 mm(P>0.05).The MAE of Barrett Universal Ⅱ formula was the smallest regardless of the axial length.In the group A and group B,the refractive error of three formulas in the ratio of ±2.00 D reach to 100%.While in group C(AL>30 mm),the refractive error of Barrett Universal Ⅱ formula in the ratio of ±2.00 D reached 100%,follow by the SRK-T and Haigis formula is 96.7% 和 93.3%.In all eyes,the three formulas are easier occur hyperopia drift.In the group of average corneal refractive power,there were no significant difference in MAE value between Barrett Universal Ⅱ formula and Haigis formula.In SRK-T formula,when corneal refractive power is too flat or too steep,the MAE is larger.Conclusion: With the increase of axial length of the eyes with high myopia,the refrative errors of the three formulas increase;Barrett Universal Ⅱ formula is the most accurate calculation formula in both eye axial grouping and corneal refractive power grouping.