AIM: To compare and modify the accuracy of the Haigis formula calculates for intraocular lens(IOL)refraction after myopic excimer laser surgery.

METHODS: The clinical records of 31 patients(31 eyes)who firstly accepted myopic corneal refractive surgery(LASIK/PRK)and then underwent phacomulsification was combined with IOL implantation in Tianjin Eye Hospital between February 2014 and March 2019 were finally enrolled in this study. Postoperative refraction was performed at least 6mo after cataract surgery. To compare the accuracy of equivalent keratometry readings(EKR)of different corneal radius(2.0, 3.0, 4.0, 4.5, 5.0mm)combined with the Haigis formula to calculate the IOL diopter after myopia, obtain the modified Haigis formula, and then compare the modified Haigis formula with the accuracy of Barrett true K, Haigis-L and Shammas-PL formulas for calculating IOL diopter after myopia.

RESULTS: The median absolute error(MedAE)and mean absolute error(MAE)of 4.0mm EKR Haigis formula was significantly lower than that of 4.5mm and 5.0mm EKR(all P<0.01). And the refractive prediction error(PE)also had a higher percentage of eyes in ±0.50D, ±1.00D and ±2.00D than that of 4.5mm EKR and 5.0mm EKR(all P<0.05). Thus, 4.0mm EKR Haigis formula was considered as the modified Haigis formula. The Postoperative MedAE of modified Haigis, Barrett true K, Haigis-L and Shammas-PL were 0.58(0.27, 1.12), 0.51(0.30, 1.15), 1.26(0.67, 1.72), 0.77(0.36, 1.45)D respectively. Moreover, the percentages of eyes with postoperative PE in ±0.50D and ±1.00D of the above formulae were 42% and 74%, 52% and 71%, 22% and 42%, 32% and 61% respectively. In eyes with axial length(AL)<27mm and 27mm≤AL≤30mm, the postoperative PE value of Haigis-L formula was higher than that of modified Haigis(P=0.019, 0.0142)and Barrett true K formula(P=0.002, <0.001 ). In patients with 27mm≤AL≤30mm, the postoperative PE value of Haigis-L formula was higher than that of Shammas-PL formula(P=0.003), and there was no significant difference among the other groups(P>0.05).

CONCLUSION: Haigis formula combined with the 4.0mm EKR can be used to calculate the IOL power in eyes after myopic LASIK/PRK, and its accuracy is comparable to the Barrett true K formula. However, the longer the AL is, the higher the possibility of hyperopic drift postoperatively might occur with the modified Haigis.