The aim of the present study was to compare conventional radial keratotomy (RK) with minimally invasive RK (mini-RK) in terms of achieved incisional depth as well as the histopathologic changes in the rabbit corneal structures. Four conventional RK incisions were performed on the right eye and four mini-RK incisions were performed on the left eye of 12 Island rabbits using a centripetal cutting technique. The corneas were excised 20 days after the procedure and examined by light microscopy. Histopathologic examination showed that the mean achieved incisional depth (73.47%) in conventional RK was consistent with the intended incisional depth (80%), However, the mean achieved incisional depth (47.28%) was far from the intended incisional depth (80%) in eyes receiving mini-RK. The difference be tween achieved incisional depth of the two surgical techniques was statistically significant (t = 10.70, P < 0.05). Corneal structural changes and epithelial plug formations were less in eyes in mini-RK than in conventional RK. These findings suggested that the refractive results in mini-RK may be less effective than conventional RK. On the other hand, in the mini-RK group, less epithelial plug formation and limited histopathologic structural alterations may have an important role in preventing long-term overcorrection and corneal rupture after ocular trauma demonstrated in conventional RK technique. (C) 1997 Japanese Ophthalmological Society.