Histological Changes and Unscheduled DNA Synthesis in the Rabbit Cornea Following 213-nm, 193-nm, and 266-nm Irradiation

ABSTRACT PURPOSE: To examine the acute outcome of corneal irradiation in adult rabbits for 193-, 213-, and 266-nm laser wavelengths. METHODS: Animals were randomly allocated to one of three groups and were treated with 213-nm quintupled Nd:YAG laser, a 193-nm excimer laser, or a 266-nm quadrupled Nd:YAG laser (n=6 per group, two exposure durations). Thermal damage was assessed histologically and the extent of DNA damage estimated by measuring unscheduled DNA synthesis in corneal epithelial and stromal cells using p 3 H thymidine autoradiography. RESULTS: For the 193- and 213-nm groups, irradiation did not induce thermal damage. Moreover, cells displaying unscheduled DNA synthesis represented <4% of the total cell numbers with no difference between groups (P>.05). By contrast, the 266-nm laser led to stromal melting and vacuolation; unscheduled DNA synthesis levels were elevated over the other groups (P<.05). CONCLUSIONS: Corneal laser ablation with the 213-nm Nd:YAG laser resulted in similarly low levels of thermal and DNA damage to those produced using the clinically accepted 193-nm excimer laser. [J Refract Surg. 2007;23:477-481.]