Accuracy of Scheimpflug Holladay equivalent keratometry readings after corneal refractive surgery.

PURPOSE To determine the accuracy of Pentacam Scheimpflug system Holladay equivalent keratometry (K) readings (EKRs) in calculating intraocular lens (IOL) power after corneal refractive surgery, including laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK). SETTING Jules Stein Eye Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, California, USA. METHODS In this combined retrospective and prospective clinical study, patients who had cataract surgery after corneal refractive surgery were recalled to have Scheimpflug imaging of the operated cornea and Holladay EKR determination. The Holladay EKR was compared with a gold-standard K value, which was the back-calculated value using the original Hoffer formula based on the actual surgical outcomes. Eyes without a history of refractive surgery served as controls. RESULTS Twenty-seven patients (41 eyes) were evaluated; 26 eyes had previous LASIK or PRK and 15, previous RK. Forty-one eyes served as controls. The mean error of the Holladay EKR in eyes with previous LASIK or PRK was +1.84 diopters (D) (range +0.66 to +4.94 D). The mean error in eyes with previous RK was +2.17 D (range +0.48 to +3.09 D). In the control eyes, the mean EKR error was +1.38 D (range -0.17 to +2.54 D). CONCLUSIONS The Holladay EKR calculated using version 1.16r04 of the Scheimpflug system software was inaccurate in virgin corneas and in those with a history of LASIK, PRK, or RK using current IOL power calculation formulas. The Scheimpflug power measurements were consistently steeper than the true corneal power.