Alterations to eye structures in hairless mice by long-term ultraviolet irradiation. A histopathological study

The eyes of 75 Hr/Hr hairless mice were irradiated with one minimal erythema dose/day of UV light for a period of 12 months, and then observed for a further 6 months. The mice were divide into 3 subgroups, - one without protectans, - one protected by the sun protection lotion Sea and Ski, factor 5, - and one by Piz Buin, Factor 6. The eyes of 75 non-irradiated mice of the same type, subdivided into 3 comparable groups, served as controls. Animals which died during the test period were examined immediately. After the 18 months period, eyes and adnexa of the surviving animals were examined macroscopically and by light microscopy. The lifespan of unprotected, irradiated mice was significantly shorter than the protected groups. The eyelids of irradiated mice presented hyperplasia, actinic keratosis and invasive carcinoma, the latter in 20%. No melanotic tumours were recorded. Since the sun lotion protected animals had a significantly longer lifespan they showed a higher number of palpebral tumours. No irradiation lesions could be demonstrated in the lens, the vitreous or the retina.