Ultraviolet B exposure and type of lens opacity in ophthalmic patients in Japan

Over the course of an individualʹs lifetime, lens fiber cells proliferate and differentiate to form various parts of the lens. The specific pathogenic effects of ultraviolet B radiation (UVB), one of the major causes of cataracts, may differ depending upon the particular part of the lens. In this study, the association of UVB exposure with specific types of lens opacity was investigated in relation to lifetime cumulative exposure, and was confirmed by subjects’ ages at exposure. The severity of lens opacities was assessed by slit lamp examination after pupil dilatation. Information on UVB exposure based on place of residence and average hours spent outdoors per day was obtained by interview for several age ranges of exposure. The effects of UVB exposure on cortical and nuclear opacities for both sexes were evaluated using logistic regression analysis. The severity of opacities was found to increase with UVB exposure. In particular, lifetime cumulative UVB exposure and exposure after the teenage years correlated with the presence of nuclear opacities in females. The results indicate that the effect of UVB exposure is greater for nuclear than for cortical opacities. This is in agreement with the proposed type-specific mechanism for lens opacities caused by UVB exposure.