Predictability of intraocular lens power calculations based on formulas on the ASCRS website after myopic laser refractive surgery

PurposeThis work was conducted in order to study the intraocular lens (IOL) power predictability of formulas provided by the American Society of Cataract and Refractive Surgery (ASCRS) website for patients who had undergone myopic laser refractive surgery.MethodsIn this retrospective study, we analyzed 11 eyes (from nine patients) that had previously undergone myopic laser-assisted in situ keratomileusis or photorefractive keratectomy and experienced subsequent phacoemulsification and posterior-chamber IOL implantation. Using the adjusted central K (keratometry), axial length, and the SRK/T formula, we compared the original desired refraction to the manifest refraction 1 month after cataract surgery. According to the postoperative manifest refraction, we compared the IOL power calculated using the different methods on the ASCRS website.ResultsBefore cataract surgery, the mean adjusted central K reading was 35.90 diopters (D) (range 29.24–41.58 D), and the mean axial length was 28.53 mm (range 25.77–32.79 mm). Postoperatively, the mean arithmetic refractive prediction error was 0.50 D (range −1.72 D to 2.33 D), and the mean absolute error was 1.07 D (range 0.01–2.33 D). The most reliable method was the Masket method in combination with the double K Holladay I formula. The predictability of the adjusted central K method and the Masket method in combination with the single-K SRK/T formula was as precise as that of the modified Masket method in combination with the double K Holladay I formula and the Shammas method in combination with the Shammas-PL formula.ConclusionASCRS offers the use of a postrefractive IOL calculator online, free of charge. The Masket method in combination with the double K Holladay I formula is the best choice for IOL power prediction after laser-assisted in situ keratomileusis or photorefractive keratectomy surgery. The adjusted central K method is a convenient and effective strategy with which to correct central corneal power. However, double K formulas designed for adjusted central K should be used for more accurate predictions of lens position