Depth of DNA photodamage in human corneas exposed to 222 nm or 254 nm UV

Within the ultraviolet C (UVC) spectrum, the wavelengths in the 200-235 nm range, here named far-UVC, have been shown to effectively inactivate a variety of pathogens. Because of their limited penetration in biological materials, far-UVC wavelengths are anticipated to be minimally damaging to human skin and eyes. The germicidal efficacy of these wavelengths combined with a predicted low health hazard for humans suggests that far-UVC sources could operate continuously in indoor locations to reduce the risk of transmission of airborne diseases among occupants. While it is well-established that exposure to far-UVC light is minimally damaging to skin, concerns remain on the safety of exposed eyes. Scientific bodies overseeing UV radiation protection recommend eye safety limits based on published peer-reviewed data. To support this goal, our previous work used a 3D model of the human cornea to assess the wavelength dependence of corneal damage induced by UVC radiation; unlike relatively longer wavelengths, far-UVC wavelengths induced DNA dimers only in the uppermost layers of the corneal epithelium. Here, similar eye safety studies were extended to excised human corneas. The depth of DNA photodamage into the corneal epithelium was evaluated after exposure of the anterior surface to 50 mJ/cm2 or 100 mJ/cm2 from 222 nm or 254 nm light.