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Lens opacities after repeated exposure to ultraviolet radiation
R Michael1, S Löfgren, P G Söderberg
1St. Erik's Eye Hospital, Karolinska Institutet, Stockholm, Sweden. ralph.michael@altavista.net
Purpose:
To investigate the effect of the interval between two, near-threshold exposures to ultraviolet radiation (UVR) on cataract development.
Methods:
One eye of Sprague-Dawley rats was exposed twice to 4 kJ/m2 narrow band UVR (lambdaMAX=300 nm) for 15 min each. The interval between exposures was 0, 6, 24 or 48 h. One week after the first exposure both lenses were removed for photography and measurement of the intensity of forward light scattering to quantify lens opacities.
Results:
All exposed lenses developed cataract. Forward light scattering was the same after double exposure with no interval or a 6 h interval. Forward light scattering after a 24 or 48 h interval was nearly twofold greater than that following no interval or a 6 h interval. The exposed lenses in all groups had mild anterior surface opacities and intense equatorial opacities as judged with a stereomicroscope.
Conclusion:
Two, near-threshold UVR exposures at 0 or a 6 h interval produce the same degree of lens opacification. When the second exposure follows 24 or 48 h after the first, lenticular damage increases. Repair processes between 24 and 48 h after exposure appear to be sensitive to UVR, and an additional exposure during this time may aggravate cataract development.