Accuracy of Scheimpflug Holladay equivalent keratometry readings after corneal refractive surgery
Received 28 July 2008; received in revised form 18 February 2009; accepted 22 February 2009.
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.
From the Department of Ophthalmology (Tang, Hoffer, Olson, Miller), David Geffen School of Medicine at UCLA and the Jules Stein Eye Institute, Los Angeles, California, USA; Department of Ophthalmology (Tang), Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
Corresponding author: Kevin M. Miller, MD, Jules Stein Eye Institute, 100 Stein Plaza, UCLA, Los Angeles, California 90095-7002, USA.
No author has a financial or proprietary interest in any material or method mentioned.
Presented in part at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Chicago, Illinois, USA, April 2008.
Supported by unrestricted gifts from John A. Lyddon and the Carl and Roberta Deutsch Foundation.
ABSTRACT