Abstract
BackgroundThe human lens is continuously exposed to high levels of light. Ultraviolet radiation is believed to play a causative role in the development of cataract. In vivo, however, the lens is mainly exposed to visible light and the ageing lens absorbs a great part of the short wavelength region of incoming visible light. The aim of the present study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet radiation.MethodsNaturally aged human donor lenses were irradiated with UVA (355 nm), violet (400 and 405 nm) and green (532 nm) lasers. The effect of irradiation was evaluated qualitatively by photography and quantitatively by measuring the direct transmission before and after irradiation. Furthermore, the effect of pulsed and continuous laser systems was compared as was the effect of short, intermediate and prolonged exposures.ResultsIrradiation with high intensity lasers caused scattering lesions in the human lenses. These effects were more likely to be seen when using pulsed lasers because of the high pulse intensity. Prolonged irradiation with UVA led to photodarkening whereas no detrimental effects were observed after irradiation with visible light.ConclusionsIrradiation with visible light does not seem to be harmful to the human lens except if the lens is exposed to laser irradiances that are high enough to warrant thermal protein denaturation that is more readily seen using pulsed laser systems.
Highlights
The human lens is continuously exposed to high levels of light
Lens chromophores are formed by a number of pathways including photochemical modification of tryptophan [5,6,7,8,9] and denaturation with sugars forming advanced glycation end products and cross-links between lens proteins [10,11,12,13]
White lesions were avoided when laser irradiance was reduced to 16 mW/cm2 but prolonged exposure (~72 hours) led to brown lesions, Figure 1
Summary
The human lens is continuously exposed to high levels of light. The lens is mainly exposed to visible light and the ageing lens absorbs a great part of the short wavelength region of incoming visible light. The aim of the present study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet radiation. The aim of the present study was to examine and compare the effects of irradiation with ultraviolet radiation and visible light on the optical properties of naturally aged human lenses. This was done by using different wavelengths of irradiation, different exposure times and irradiation levels, and pulsed and continuous wave laser systems. The effect of the irradiation was documented qualitatively by photographs and quantitatively by measuring the direct transmission of white light before and after irradiation
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