Evaluation of acute corneal damage induced by 222-nm and 254-nm ultraviolet light in Sprague–Dawley rats

Abstract

Two hundred twenty-two nanometres ultraviolet (UV) light produced by a krypton–chlorine excimer lamp is harmful to bacterial cells but not skin. However, the effects of 222-nm UV light exposure to the eye are not fully known. We evaluated acute corneal damage induced by 222- and 254-nm UV light in albino rats. Under deep anaesthesia, 6-week-old Sprague–Dawley albino rats were exposed to UV light. The exposure levels of corneal radiation were 30, 150, and 600 mJ/cm2. Epithelial defects were detected by staining with fluorescein. Superficial punctate keratitis developed in corneas exposed to more than 150 mJ/cm2 of UV light, and erosion was observed in corneas exposed to 600 mJ/cm2 of UV light. Haematoxylin and eosin staining also showed corneal epithelial defects in eyes exposed to 254-nm UV light. However, no damage developed in corneas exposed to 222-nm UV light. Cyclobutane pyrimidine dimer-positive cells were observed only in normal corneas and those exposed to 254-nm UV light. Although some epithelial cells were stained weakly in normal corneas, squamous epithelial cells were stained moderately, and the epithelial layer that was detached from the cornea exposed to 600 mJ/cm2 of light was stained intensely in corneas exposed to 254-nm UV light. In the current study, no corneal damage was induced by 222-nm UV light, which suggested that 222-nm UV light may not harm rat eyes within the energy range and may be useful for sterilising or preventing infection in the future.