The crystalline lens of the human eye absorbs most of the incident ultraviolet radiation (UVR), but when the lens is removed, this radiation can reach the photoreceptors. The consequences of UVR exposure on cone receptor sensitivity were determined from psychophysical measurements in patients who had undergone bilateral cataract extraction and implantation of intraocular lenses (IOLs). The IOL implanted in one eye contained chromophores that absorb incident UVR, whereas that implanted in the other eye transmitted UVR. Five years of exposure to ambient UVR was associated with a selective loss in sensitivity of the short-wave cone photoreceptors. These results are consistent with the hypothesis that chronic exposure to UVR may damage the human retina.