The effect of ultraviolet B (UV-B) radiation and a vitamin C-deficient (VCD) diet on guinea pig lenses was investigated. The initial lens changes in the VCD group were observed by slit-lamp examination 6 weeks after the start of the VCD treatment; after 12 weeks the changes in the posterior subcapsular region became more prominent, and the dissociation around the posterior suture became wider and slightly deeper toward the posterior cortex. The high concentration of lens oxidized glutathione (GSSG), and the low ratio of reduced glutathione (GSH) to oxidized glutathione (GSH/GSSG) on the lens posterior region correlated with density changes in the corresponding layers as measured by Scheimpflug images with linear microdensitometry. It is suggested that the strong oxidative stress of the VCD diet caused the damage at the posterior part of the lens. UV-B radiation appeared to accelerate cataract progression in lenses that lack vitamin C.