Corneal lathing using the excimer laser and a computer-controlled positioning system

PURPOSE: To present the excimer laser corneal shaping system (ELCS-S), an a dd-on device to the Keratom, a commercially available 193-nm excimer laser built by Schwind. METHODS: The system is designed for the preparation of donor corneas under sterile conditions using the ultraviolet laser to offer greatest possible f lexibility. Lenticules for planolamellar grafting and refractive epikeratop lasty, as well as donor buttons for penetrating keratoplasty can be compute r-designed by the surgeon or technician and lathed with the system. RESULTS: Using the excimer laser corneal shaping system (ELCS-S) on human d onor corneas, the central surface of the epikeratoplasty lenticule exhibite d only narrow, flat concentric notches corresponding to the single lathing steps. Transmission electron microscopy revealed a damage zone of less than 0.3 mu m in close approximation to the treated surface. The final thicknes s revealed a difference of less than +/-53 mu m from the intended, initiall y programmed value. Ultrastructural studies showed the perpendicular stroma l surface of the penetrating keratoplasty buttons to be smooth with minimal protrusion of Descemet's membrane. Endothelial injury was observed in a zo ne averaging between 40 and 100 mu m adjacent to the cutting edge only. CONCLUSION: The excimer laser corneal shaping system (ELCS-S) allows a comp uter-controlled, surgeon-designed, sterile preparation of lamellar and pene trating corneal grafts with the use of the excimer laser. This could offer significant advantages in comparison to presently available systems for lam ellar dissection and trephination.