Pentacam Assessment of Posterior Lamellar Grafts to Explain Hyperopization after Descemet's Stripping Automated Endothelial Keratoplasty

Purpose: To evaluate changes in posterior corneal curvature as a possible cause of the hyperopic refractive shift observed after Descemet's stripping automated endothelial keratoplasty (DSAEK). Design: Prospective, noncomparative, interventional case series. Participants: Thirty-four eyes of 29 patients with Fuchs' endothelial dystrophy or pseudophakic bullous keratopathy. Methods: A standard DSAEK procedure was performed in 34 eyes using the pull-through technique for graft delivery. When cataract was present (n = 7), phacoemulsification with posterior chamber intraocular lens implantation was combined. Each eye underwent Pentacam (Oculus, Wetzlar, Germany) evaluation 1, 3, and 12 months after surgery. Corneal graft thickness was calculated on Scheimpflug scans at 9 locations (1 central, 4 peripheral, and 4 mid peripheral). The mean radius of posterior corneal curvature (Rm) was recorded. At each postoperative examination time, manifest refraction was determined and compared with pre-DSAEK values in simple procedures or with intended postoperative refraction, if cataract surgery had been performed. Main Outcome Measures: Manifest refraction, Rm, and corneal graft thickness at 1, 3, and 12 months after surgery. Results: The mean±standard deviation posterior corneal curvature was 6.5±0.56 mm before surgery and varied from 5.52±0.39 mm 1 month after surgery to 5.83±0.37 mm at 3 months after surgery and 5.92±0.35 mm at 12 months after surgery. The grafts were significantly thicker in the periphery and mid periphery than in the center at all examination times. Thickening diminished significantly over time at all locations. The average reduction of corneal thickness was higher at the edges (91.5 μm) than in the mid periphery (38.3 μm) or in the center (24.2 μm). The average postoperative spherical equivalent±standard deviation changed from -0.31±2.35 diopters (D) before surgery to 1.03±2.21 D 1 month after surgery, 0.61±2.07 D 3 months after surgery, and +0.31±2.03 D 12 months after surgery. Conclusions: The difference in thickness between center and periphery of the DSAEK graft induces a change in posterior corneal curvature, resulting in a hyperopic shift that decreases with time and is negligible for spectacle correction. However, when performing a triple procedure, intraocular lens selection should take into account the refractive change induced by DSAEK.