The purpose of this study is to evaluate the effect of Mytomycin-C on the Corneal Endothelium during Excimer Laser Surface Ablation. This clinical trial was unicenter, prospective, interventional, masked study, conducted at Basir eye center, Tehran, Iran. Bilateral myopic patients scheduled to have surface ablation procedure were recruited. The inclusion criteria was ablation depths less than 65 µm. Patients with unstable refraction, suspicious of keratoconus, excessive dry eyes, impaired wound healing processes, lenticular changes, corneal dystrophy, history of ocular surgery, anterior or posterior uveitis, glaucoma, retinal diseases, and also ablation depths of 65 µm or more were excluded. Sample size is 100 patients. One eye was randomly assigned to receive intraoperative topical MMC, and Balanced Salt Solution (BSS) was used in the fellow eye of the same patient. The outcome measure of the study is endothelial cell density 3 and 6 months post surgical.