Ultraviolet radiation and cataract: a review of the epidemiological evidence.

There is considerable international interest in the scientific community about the association between solar ultraviolet B radiation (UVB) and cataract.Much of this interest has resulted from concern about the health effects of the increasing levels of UVB reaching the earth's surface as a conse- quence of depletion of the stratospheric ozone layer.Ophthalmologists have been suggesting an association between sunlight and cataract since the early part of the twentieth century.'-3Only in the past 20 years have epidemio- logical studies documented the association.Recently, polarised views have been expressed about the importance of the association.At one pole is Young who suggests that sunlight is the primary causal factor in cataract- ogenesis, and strongly advocates the widespread distribution ofsunglasses to prevent cataract.4At the other pole is Harding who suggests that sunlight is not a major factor in human cataract.5These opposing views have been published recently in international ophthalmic journals and books.67Unfor- tunately, ophthalmologists are left not knowing which view represents a balanced assessment of the data.The polarised assessments of Young and Harding are based on the same available evidence which strongly suggests that one, if not both, ofthe views is based on the selective use and interpreta- tion of the literature.In this review I, as an epidemiologist, assess the epidemio- logical information objectively to determine if there is sufficient evidence to show that exposure to solar UVB is causally associated with the development of human cataract.