is an important factor in experimental UVR cataract
Stefan Löfgren, Ralph Michael, Marcelo Ayala & Per G Söderberg
Poster submitted to the "Protection Against the Hazards of UVR" Internet conference Jan 1999
AbstractPurpose. To investigate the effect of age and post-exposure time on ultraviolet radiation (UVR) induced cataract.
Methods. 140 albino Sprague-Dawley rats, divided into the ages 3, 6, 17 and 52 weeks and two post-exposure time groups (1 and 8 w), were unilaterally exposed in vivo to UVR-300 nm. The dose incident on the cornea was 8 kJ/m2. The rats received mydriatic (pupil-dilating) eye drops before the irradiation. One week after exposure the lenses were extracted, photographed and the degree of forward light scattering (cataract) was measured.
Results. Preliminary data analysis showed that the younger rats were much more sensitive to UVR than the older rats. The radiation dose was so high that many lenses went totally opaque. The number of opaque lenses was higher after eight weeks than after one week post-exposure.
Conclusions. Young animals are more sensitive to UV radiation than old animals.
IntroductionCataract is a major cause of blindness in the world. The surgical treatment of cataract where the lens is replaced by a artificial lens is very costful for the society. Scientists are trying to find the cause of cataract and possible medical treatments or preventive measures in order to reduce the suffering of the affected patients and to lessen the burden on the health care systems. Several hypotheses have been put through, among them the hypothesis that UVR in sunlight is an important risk factor for development of cataract. Epidemiological studies have shown a link between exposure to UV-B radiation in sunlight and development of cataract. Experimental studies confirm that UVR induces cataract. The safety levels for UVR exposure today are based on experiments with animals. There is however a lack of data on the age dependence in experimental UVR cataract. In this study the age dependence and post-exposure time are investigated in a rat model.
ResultsPreliminary data analysis shows that
DiscussionYounger rats developed more severe cataract. This is new information which not has been taken into consideration when current safety limits for UVR exposure was established. It may also have implications in ophthalmic laser treatment in children.
Why are young rats more sensitive to UV radiation?
There are some factors which we believe may explain this. Suggestions on other possible factors are welcome!