Evaluation of intraocular lens power prediction methods using the American Society of Cataract and Refractive Surgeons Post-Keratorefractive Intraocular Lens Power Calculator

Abstract

Methods using surgically induced change in refraction and methods using no previous data gave better results than methods using pre-LASIK/PRK K values and surgically induced change in refraction.

Corneal power estimation for intraocular lens power calculation after corneal laser refractive surgery in Chinese eyes

“…One is the erroneous estimation of corneal power due to altered corneal geometry. [1][2][3][4] The other source is the inaccurate prediction of IOL position (effective lens position [ELP]) by using the corneal radius after refractive surgery. The latter can be avoided by using the Aramberri double-K modification of theoretical formulas or the Haigis formula.…”

“…[1][2][3][4][5] The proposed solution to this error is to evaluate the corneal refractive surfaces separately 5 using devices that can measure both corneal surfaces. These devices include a rotating Scheimpflug camera (Pentacam, Oculus, Inc.), 6,7 a dual Scheimpflug analyzer (Galilei, Ziemer Ophthalmics AG), 8,9 a vertical slitlight scanning device (Orbscan, Bausch & Lomb, Inc), 10,11 and optical coherence tomographers.…”

Intraocular Lens Power Calculations in Eyes with Prior Corneal Refractive Surgery

“…Using this calculator, our study of 72 post-LASIK/PRK eyes that had cataract surgery found that, compared to methods requiring pre-LASIK/PRK Ks and ∆MR, methods using ∆MR or using no prior data had smaller IOL prediction errors, smaller variances, and greater percentage of eyes within 0.5 and 1.0 D of refractive prediction errors [5]. Another excellent resource is a comprehensive spreadsheet developed by Kenneth Hoffer and Giacomo Savini (http://www.eyelab.com/) [4].…”

May consultation #2

“…We do not have the 6-month postoperative K readings and have to assume that they are the same as the current K values. We are also missing standard topographic data, such as the Atlas numerical map (Carl Zeiss Meditec AG) and the Pentacam equivalent K reading for the central 4.5 mm, as described by Holladay et al 1 The remaining methods result in lower IOL powers; the Shammas, Haigis-L, and modified Masket formulas yield 14.61 D, 13.89 D, and 13.48 D, respectively. The ASCRS mean value recommends using an Acrysof SN60WF IOL (Alcon Laboratories, Inc.) with a power of 14.17 D (range 13.02 to 14.92 D).…”

“…Both Holladay and Haigis believe that the clinical history method (CHM) provides the most reliable estimate; thus, we would aim closer to 14.77 D and choose an Acrysof SN60WF 14.50 D IOL in this case. 1,3 A conservative approach should always err on the side of myopia, and picking the same IOL with a 15.00 D power is also reasonable. Other considerations include a surgeon's individual correction factors.…”