Morphometric Analysis of the Corneal Endothelium Following LASIK versus PRK - A One-Year Confocal Microscopic Study

Abstract

Abstract: : Purpose: Excimer laser refractive surgery may potentially damage the corneal endothelium by inducing cell loss or harmful morphometric changes. With LASIK the photoablation occurs under a lamellar flap, placing the laser energy closer to the endothelium than with PRK. This study evaluates the effects of LASIK versus PRK on the corneal endothelium during the first year post-surgery. Methods: 35 eyes of 35 myopic patients (-6.0 to -8.0 D) were randomized to either LASIK (n=20) or PRK (n=15) and treated using a MEL70 excimer laser. Patients were examined preoperatively and at 3, 6, and 12 months using Tandem Scanning Confocal Microscopy. From each examination, 150-200 endothelial cells were evaluated using "Endomorph"; a novel software program for accurate morphometric analysis. Results: No significant changes in corneal endothelial cell density could be identified following either LASIK or PRK. The data in the Table are corrected for changes in the absolute distance from the objective surface to the image plane (0.0104% magnification per µm depth). However, the data are not corrected for the physiological cell loss (averaging 10 cells/mm² annually). Interestingly, both LASIK and PRK induced a significant increase in the "Circular Form Factor"; a more sensitive morphometric parameter for altered endothelial cell homeostasis. . Conclusions: Neither LASIK or PRK are associated with significant changes in corneal endothelial cell density during the first year post-surgery. However, both techniques appear to induce discrete morphological changes in the endothelium. Longer follow-up of this cohort will reveal the clinical importance of this observation. Corneal endothelial cell density after LASIK vs. PRK (cells/mm²)  

Keywords: refractive surgery: LASIK • refractive surgery: complications • cornea: endothelium