To compare differences in the endothelial cells before and after photorefractive keratectomy (PRK) for myopia with refractive error graded Mitomycin C (MMC) application.

In a prospective randomized clinical trial, forty eight myopic patients were treated with PRK by a Bausch & Lomb Technolas 217z excimer laser. MMC was applied after PRK five seconds for each diopter of spherical equivalent refractive error corrected. The manifest refraction, visual acuity, MMC treatment length, corneal pachymetry and specular microscopy were evaluated preoperatively and at 1 and 6 months postoperatively.

A total of 48 cases (96 eyes, 68.75% female) were treated, with a mean age of 26.70 ± 4.89 years (range, 18–34 years). Postoperativecell density, cell size and polymegathelism did not significantly change. On the other hand, standard deviation (SD) of cell size (p=0.008), pleomorphism (p=0.003) and coefficient of variation (CV) (p=0.016) were significantly increased. None of these parameters was related to the length of MMC application. Corneal thickness decreased significantly after the operation but it increased 6 months postoperatively compared with the first month (p<0.001).

MMC application for PRK in myopia can affect the endothelial cells, but in early follow ups, it does not affect the cell density or size. Cell size was changed but it was obvious not in mean cell size, but in SD and CV. MMC time below the 30 seconds was not significant on endothelial cell changes.