UV-mediated cataractogenesis: a radical perspective.

A number of epidemiologic and experimental studies indirectly support the idea that solar ultraviolet radiation may be cataractogenic. However, the physical and cellular processes which might be involved in such cataractogenesis are by no means clear. Because a major consequence of the UV irradiation of oxygenated organic matter is the production of activated oxygen species, the involvement of oxidants has been suspected to be of importance. However, because the lens may normally exist in an hypoxic or even anoxic environment, the extent of availability of oxygen for such reactions is presently unknown. So also are the possible mechanism through which putative UV damage of the lens might eventuate in cataract. In addition to possible rapid and direct lethal damage to lens epithelium, possible cumulative damage to both lenticular DNA and proteins may occur. Furthermore, UV radiation has the potential to photolytically destroy light-sensitive nutrients and to generate damaging oxidants through interaction with ferruginous compounds. Given that Nature has probably provided the lens with substantial protective devices to ward off damaging effects of UV light, it is still an open question as to whether solar radiation contributes to cataract formation and, if so, by what mechanisms.