Recent developments in vision research: light damage in cataract.

Cataract is the leading cause of blindness in the world, accounting for nearly half of the 38 million cases of blindness worldwide. Age-related cataract is a multifactorial disease, and the prevalence of cataract approximately doubles with each decade after the age of 30. For this reason, if an intervention were able to delay the onset of cataract by 10 years, the number of cataract operations could be nearly halved. Possible risk factors for cataract include ultraviolet B radiation (UV-B), diabetes, alcohol, smoking, diet, diarrhea, steroid use, and certain medications such as corticosteroids." Matters are complicated because age-related cataract is not a single disease but, rather, three different types of lens changes—cortical, nuclear, and posterior subcapsular (PSC) opacities. Each has its own pathogenic changes, age distribution, and almost certainly different risk factors. The investigation of UV-B as a risk factor for cataract has received considerable attention and has increased recently for several reasons. Sunlight is the principle source of UV-B for the majority of the world's population, and depletion of the stratospheric ozone will lead to UV-B exposure of higher intensity/ Even if the relative risk for cataract development from UV-B exposure were relatively low, the public health significance could be great because nearly everyone is exposed to UV-B. The changing demographics of the world's population, caused by the increasing proportion of the elderly, and the thinning of die stratospheric ozone increase the urgency to quantify the possible effect of UV-B on the development and progression of lens opacities. This information is needed so that appropriate public health interventions can be implemented if necessary. Ultraviolet radiation is usually divided by wavelength into UV-A (400 to 320 nm), UV-B (320 to 290 nm), and UV-C (<290 nm). Incident UV-B varies greatly by time of day, altitude, and season. The ozone layer absorbs almost all UV-C, thus preventing it from reaching the eye lens. Any UV-C diat is encountered