Background: The human lens is continuously exposed to high levels of light. Ultraviolet radiation is believed to\r\nplay a causative role in the development of cataract. In vivo, however, the lens is mainly exposed to visible light\r\nand the ageing lens absorbs a great part of the short wavelength region of incoming visible light. The aim of the\r\npresent study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet\r\nradiation.\r\nMethods: Naturally aged human donor lenses were irradiated with UVA (355 nm), violet (400 and 405 nm) and\r\ngreen (532 nm) lasers. The effect of irradiation was evaluated qualitatively by photography and quantitatively by\r\nmeasuring the direct transmission before and after irradiation. Furthermore, the effect of pulsed and continuous\r\nlaser systems was compared as was the effect of short, intermediate and prolonged exposures.\r\nResults: Irradiation with high intensity lasers caused scattering lesions in the human lenses. These effects were\r\nmore likely to be seen when using pulsed lasers because of the high pulse intensity. Prolonged irradiation with\r\nUVA led to photodarkening whereas no detrimental effects were observed after irradiation with visible light.\r\nConclusions: Irradiation with visible light does not seem to be harmful to the human lens except if the lens is\r\nexposed to laser irradiances that are high enough to warrant thermal protein denaturation that is more readily\r\nseen using pulsed laser systems.
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