Data will be collected on the safety and efficacy of performing excimer laser photorefractive keratectomy in two animal models. A previously developed 193 nm excimer laser system, the ExciMed UV200, will be used to perform photorefractive keratectomy using two different treatment techniques. The ExciMed UV200 with an electronically driven iris aperture delivery system will be compared to an ExciMed UV200 with a fixed beam diameter used in conjunction with an ablatable contact mask. A comparison will be made of the two methods in rabbits and monkeys. In Phase I, initial development of the contract mask will be performed and a range of operating parameters for performing photorefractive keratectomy with the contact mask will be determined in-vitro. Simultaneously, in-vivo experiments in rabbits and monkeys will begin with the previously developed iris aperture delivery system. During Phase II, in-vivo work will be performed in rabbits and monkeys with the ablatable contact mask. Further development of the contact mask will take place during Phase II based on the results of the in-vivo experiments. Analysis of the data collected in rabbits and monkeys will determine which of the two treatment techniques will be used in further human clinical trials of photorefractive keratectomy.