The studies of the effects of different lasers on the cornea have usually been done on animals. These studies show that ultra-violet lasers (Excimer 193 nm, 213 nm) have a pure photo-ablative effect, without distant lesions. The corneal endothelium is always intact as long as the laser beam is acting at a distance of more than 50 microns from the cells. The same findings after photo-ablation is the presence of a fibroblastic scar after epithelial healing. This scar correspond to the haze observed in clinical conditions. The infra-red lasers (Intrastomal YAG) produce an important thermal effect the corneal stroma and a destruction of the corneal endothelium if influence and frequency are increased. In conclusion, the lasers used in corneal surgery appear to be safe for the corneal structure but histological studies remain necessary for the new lasers in order to be certain of their safety.