Postmortal epithelial changes of donor corneas impair applicability of a refractive ultraviolet femtosecond laser

This study evaluates the corneal applicability of a refractive ultraviolet femtosecond laser in postmortal human donor eyes and ex vivo porcine eyes. Refractive lenticule extraction and flap creation were attempted in 10 human donor eyes and 80 ex vivo porcine eyes with and without abrasion of the corneal epithelium. The postmortem interval ranged from 6 to 35 h in the human samples and was set to 4, 24, and 48 h for the porcine specimens. Nine human eyes and 60 porcine eyes were treated with an ultraviolet femtosecond laser. The rest was treated with an infrared laser. Optical coherence tomography and scanning electron microscopy were used to demonstrate success or failure of the procedures. Ultraviolet laser-assisted refractive surgery attempts without prior abrasion of the corneal epithelium were only successful at 6 h p.m. in the human eyes and at 4 and 24 h in the porcine eyes. Upon epithelial abrasion, refractive surgery was always successful with the ultraviolet laser. The infrared laser always performed successfully with and without prior epithelial abrasion. Thus, postmortal changes in the corneal epithelium impair the ability of refractive ultraviolet femtosecond lasers to create stromal cuts. This progresses with time but does not affect infrared femtosecond lasers.