Laser shaping of corneal transplants in vitro: area ablation with small overlapping laser spots produced by a pulsed scanning laser beam using an optimizing ablation algorithm

Area laser lathing and trephination of donor corneas is used to produce dif ferent types of grafts for human transplantation. 193 nm (ArF excimer) lase r radiation is used, since this is known to give a non-thermal laser-tissue interaction with a minimal zone of tissue damage. To guarantee the highest degree of flexibility concerning the overall shape of the grafts as well a s their thickness profiles, we use a small (compared with the area to be ab laled) scanning laser spot. For area lathing of the tissue we have develope d a new ablation algorithm (optimized scanning laser ablation, OSLA) that c an be applied to lathe and perforate any tissue-with concave las in this ap plication), convex or plane surface geometry-where surface precision and sm oothness are key issues. Using OSLA with the Excimer Laser Corneal Shaping System (a tool for in vit ro fabrication of all kinds of corneal transplants like donor buttons for k eratoplasty, lamellar grafts for epikeratoplasty and refractive lenticules) enabled us to produce ail types of corneal grafts with very high precision . This is considered to be a major improvement towards the production of re fractive lenticules.