Intraocular lens power calculations after refractive surgery

Abstract

Objective To investigate the refractive outcomes of intraocular lens (IOL) power calculations after refractive surgery with equivalent keratometry readings (EKR) and the double-K adjustment of the Holladay I formula. Methods In this retrospective study, 45 eyes of 32 patients undergoing phacoemulsification and IOL implantation after myopic laser in situ keratomileusis or photorefractive keratectomy were enrolled. Corneal power was obtained with a Pentacam and IOL Master. The IOL power was calculated by three methods: EKR, a clinical history and the Haigis-L formula. Final postoperative refraction was measured 1 month after the surgery. The median absolute error (MedAE) and the mean absolute error (MAE) of postoperative refraction were compared with those from the Haigis-L formula and the clinical history. The Kruskal-Wallis test was used to compare MedAE and one-way ANOVA was used for MAE. The accuracy of the EKR method was compared with other popular IOL calculation formulas for use in eyes after LASIK or PRK. Results EKR achieved the greatest predictive accuracy (P<0.05) , with a MedAE of 0.32 D and MAE of 0.39 D. Seventy-one percent of eyes were within ±0.50 D and 93% were within ±1.00 D of the EKR predicted outcome. This was significantly more accurate than the other preoperative methods: MedAE was 0.51 D and was 1.48 D for the Haigis-L method and the clinical history, respectively. Conclusion The IOL power estimation in challenging eyes with prior LASIK or PRK is most accurately predicted by EKR. Key words: Equivalent keratometry readings; Intraocular lens power calculations; Refractive surgical procedures