We examined phenotypic changes during the wound healing process in the corneal epithelium of Goto-Kakizaki (GK) rats, a spontaneous model of type 2 diabetes mellitus. In this article, we provide an overview of our and other groups' research and describe the clinical features of diabetic keratopathy. We observed that the rate of corneal epithelial wound closure was decreased in GK rats compared with Wistar rats. Immunoreactivity for Cx43, K14, and Ki-67 was detected in the 2 layers of cells adjacent to the basement membrane in the corneal epithelium of GK rats, whereas only the single basal layer of cells was positive for these proteins in the corneal epithelium of Wistar rats. The frequency of Ki-67-positive cells was greater in GK rats than in Wistar rats in the intact corneal epithelium and during wound healing. The GK rat represents delayed corneal epithelial wound closure as well as that which is observed in human diabetic keratopathy. Furthermore, these results indicate a possibility of functional deviation in corneal epithelial cells with diabetes mellitus.