EFFECT OF SURFACE PHOTOREFRACTIVE KERATECTOMY AND LASER IN-SITU KERATOMILEUSIS ON THE CORNEAL ENDOTHELIUM

Purpose: To investigate endothelial cell loss in pairs of fresh human autopsy globes following high-diopter myopic photorefractive keratecto my (PRK) or laser in situ keratomileusis (LASIK). Setting: Center for Research on Ocular Therapeutics and Biodevices and Magill Laser Center for Vision Correction, Storm Eye Institute, Charleston, South Carolin a, USA. Methods: In the first part of the study, 12 globes had either -10 diopter (D) multizone surface PRK or -10 D single-zone LASIK. In t he second part, three groups of 5 globes each had -15 D, -20 D, or -25 D multizone-blend LASIK procedures. Fellow globes in both groups were used as untreated controls. Corneoscleral buttons were excised from a ll globes. Following 7 days in corneal organ culture, the endothelial surface was stained with two vital dyes: calcein-AM and ethidium homod imer. Fluorescence microscopy was used to obtain endothelial cell coun ts. Results: The mean dead cells per square millimeter (cells/mm(2)) w ere 0.94 in the -10 D PRK treated corneas compared with 0.91 in the fe llow untreated eyes (P = 0.06). The mean dead cells/mm(2) in the -10 D single-zone LASIK-treated corneas and in the fellow untreated eyes we re 0.61 (P = 0.88). The mean dead cells/mm(2) in the -15 D, -20 D, and -25 D multizone-blend LASIK-treated corneas were 3.08, 2.33, and 5.55 , respectively, compared with 3.49, 1.92, and 5.01 in the fellow untre ated eyes (P = 0.276, P = 0.339, and P = 0.427, respectively). Dead ce ll counts for treated and control paired corneas were highly correlate d in all treatment groups. Conclusions: No significant endothelial cel l loss occurred after -10 D PRK or LASIK corrections up to -25 D. Alth ough this study has limitations that prevent direct extrapolation to t he clinical situation, it does afford a comparable clinical correlate for endothelial cell toxicity following typical excimer laser ablation s.