Optical effects of exposing intact human lenses to ultraviolet radiation and visible light

<p>Abstract</p> <p>Background</p> <p>The 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.</p> <p>Methods</p> <p>Naturally 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.</p> <p>Results</p> <p>Irradiation 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.</p> <p>Conclusions</p> <p>Irradiation 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.</p

Structural changes of alpha-crystallin during heating observed with small and wide angle X-ray scattering

The small heat shock protein (sHSP) α-crystallin occurs in nearly all the major tissues of the body. It has two main functions; helping maintain transparency in the eye lens and as a molecular chaperone. We have investigated α-crystallin gels over a temperature range from 20 to 70oC using wide and low angle X-ray scattering techniques. The low angle data show a moderate increase in both the spacing and intensity of the reflection from 20 to 45oC. This was followed by a dramatic increase from 45 to 70oC. Upon cooling, this effect was found to be irreversible over an eleven-hour period. Wide-angle scattering reflections from the α- crystallin gel arise from the secondary structure organisation, and can be characterized by inter-sheet (a ring at ~10 Å) and intra-sheet (a ring at 4.7 Å) interactions which appear to respond differently to increasing temperature. However, no indications of denaturation or unfolding are noticeable throughout the temperature range

Structural changes in -crystallin and whole eye lens during heating, observed by low angle x-ray diffraction.

Whole eye lens and ?-crystallin gels and solutions were investigated using X-ray scattering techniques at temperatures ranging from 2