Multivariate model of refractive shift in Descemet-stripping automated endothelial keratoplasty
Accepted 28 November 2007.
Purpose
To relate in situ graft shape in Descemet-stripping automated endothelial keratoplasty (DSAEK) to surgically induced refractive error.
Setting
Academic eye institute.
Methods
High frequency arc-scanning ultrasound was performed in 7 patients enrolled in a prospective study of microkeratome-assisted endothelial keratoplasty approved by the Investigative Review Board. A region of interest spanning the horizontal meridian was defined for analysis of epithelial, host, graft, and total corneal thicknesses. Graft thickness profiles were fit by quadratic polynomials where the 2nd-order coefficients represent the posterior corneal curvature contributed by the graft. The curvature coefficient and central graft thickness were analyzed as predictors of induced refractive error.
Results
At final follow-up (mean 5.9 months ± 3.2 [SD]), 3 patients had a hyperopic shift (+2.50 diopters [D] each), 3 had insignificant (< 0.50 D) refractive shifts, and 1 had a myopic shift. In the group with hyperopic shift, a negative lens effect was predicted by positive curvature coefficients, representing grafts that were thinner centrally than peripherally (mean +22.72 μm/mm2; range +4.95 to +45.17 μm/mm2). In the group with minimal refractive shift, coefficients were less positive (mean +7.28 μm/mm2; range +2.01 to +13.82 μm/mm2). The patient with a myopic shift (−1.00 D) had the only negative curvature coefficient (−0.64 μm/mm2). In a 2-predictor model of refractive shift, central graft thickness and the curvature coefficient together accounted for 86% of the variance in the refractive response to DSAEK (P = .025).
Conclusion
Nonuniform thickness profiles and variable central graft thicknesses both contribute to refractive shift after DSAEK.
From the Cole Eye Institute (Dupps, Qian, Meisler) and Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
Corresponding author: William J. Dupps Jr, MD, PhD, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue/i-32, Cleveland, Ohio 44195, USA.
No author has a financial or proprietary interest in any material or method mentioned.
Supported in part by a Research to Prevent Blindness Challenge Grant to the Department of Ophthalmology of the Cleveland Clinic Lerner College of Medicine and NIH 8K12 RR023264 Multidisciplinary Clinical Research Career Development Programs Grant (Dr. Dupps) and NIH 1L30 EY017803-01 (Dr. Dupps). Dr. Dupps is a recipient of a Research to Prevent Blindness Career Development Award.
Karen King provided expert assistance with the arc-scanning ultrasound examinations.
ABSTRACT