OBJECTIVE To evaluate the morphometric and fluorophotometric characteristics of corneal endothelium after an eight-incision radial keratotomy (RK). METHODS A total of 43 eyes of 26 patients underwent RK and 44 eyes of 23 patients were used as age-matched controls. All patients underwent specular microscopic and fluorophotometric examinations. Endothelial cell density [(ECD), cells/mm2], mean cell area [(MCA), microm2], coefficient of variation (CV) for cell area, and percentage (%) of hexagonal cells were measured by specular microscopy. Cornea-to-anterior chamber transfer coefficient (kc.ca, 10(-3) min(-1)) and corneal endothelial permeability (10(-4) cm/min) were measured by fluorophotometry. RESULTS Morphometric and fluorophotometric characteristics were similar in both the RK and control groups. Among patients in the RK group, the size of optical zone and the depth of corneal incision did not affect postoperative endothelial morphology or permeability. Those who presented for postoperative examination later than 3 months compared with those presented within 3 months of RK had lower CV for cell area; 0.28 +/- 0.04, 0.23 +/- 0.04, and 0.23 +/- 0.03, a higher percentage of hexagonal cells; 64.7 +/- 8.0, 71.7 +/- 7.8, and 72.2 +/- 6.5, and lower permeability; 5.7 +/- 1.9. 4.5 +/- 0.9, and 5.2 +/- 1.1, at <3 months, between 3 and 6 months, and >6 months after RK, respectively (all p < 0.05). In the eight cases of anisometropia, the operated eyes had a lower ECD; 3,079 +/- 429, and 3,217 +/- 495, a higher MCA; 330.6 +/- 48.1 and 317.6 +/- 50.5, and a higher endothelial permeability; 6.3 +/- 1.5 and 4.7 +/- 1.3 in the operated and unoperated eyes, respectively, at 3.4 months after RK (p < 0.05). CONCLUSIONS RK induced a minimal acute and nonprogressive endothelial loss. The transient increase in permeability within 3 months may be due to a reversible endothelial dysfunction induced by RK.