Pachymetric Ratio No-History Method for Intraocular Lens Power Adjustment after Excimer Laser Refractive Surgery

Abstract

To evaluate a new pachymetric method not requiring pre-refractive surgical data for adjusting the intraocular lens (IOL) power in eyes undergoing cataract surgery after excimer laser refractive surgery and comparing final refractive results with previously published formulas or methods. Retrospective noncomparative case series. Thirty-six eyes from 23 patients who had uneventful phacoemulsification cataract surgery after previous myopic (35) or mixed astigmatism (1) excimer laser photoablation. A new corneal ratio (Geggel ratio) method was developed to estimate the diopters (D) of previous excimer treatment or change in spherical equivalent (SE) at the corneal plane. A regression formula, 0.40 (|DeltaSE|-1), predicted the correction factor to be added to the SRK/T (Sanders, Retzlaff, Kraff) formula. The IOL results from the Geggel and Geggel-real (modified for mild myopia) method were compared with the Masket, Koch double K table, Ladas, Walter, modified Maloney, clinical history, Feiz standardized and nomogram, Latkany average and flat, Ferrara, Rosa, Savini, Jin, Shammas no-history and regression formula, Seitz, and Awwad methods. The SRK/T, Hoffer, and Holladay formulas were tested in appropriate formulas. All IOL powers were converted to refractive results using IOL(exact) equations. Mean +/- standard deviation (SD), range, absolute mean +/- SD, and percent within +/-0.5 D, +/-1.0 D, and -1.0/+0.5 D. The pachymetric technique minimizes hyperopic surprises with 92% of eyes within -1.0/+0.5 D and no overcorrections >0.5 D with the Geggel-real modification. Final refractive results with the Geggel, Geggel-real, Masket, Koch double K tables, Latkany average and flat, Savini, Shammas no-history, Seitz Holladay, Seitz Hoffer, and Awwad Hoffer all had >55% SE +/-0.5 D and >85% SE +/-1.0 D of the surgical goal. The best results with fewer hyperopic overcorrections were found in 5 methods that comprise a new consensus group: Geggel-real, Shammas no-history, Savini, Latkany flat, and Seitz Hoffer. The consensus group had 96% of eyes within -1.0/+0.5 D of the surgical goal. The Geggel-real method is a new approach requiring no historical data to determine IOL power in this ever-enlarging and challenging group of former refractive surgery patients undergoing routine cataract surgery. The author(s) have no proprietary or commercial interest in any materials discussed in this article.