are also changes due to loss of cells in the visual cortex that reduce the likelihood that correction via lenses will restore youthful vision.
Disease processes also contribute to the increased risk of loss of visual function with age. These nonnormative changes include glaucoma, macular degeneration, and cataract. Some of these diseases are linked to high blood pressure and diabetes. Cigarette smoking is also a well-established risk factor (Smith et al., 2001). Not well understood is the extent to which these changes are related to work environment factors. Lifetime exposure to ultraviolet light, which is higher for outdoors (blue-collar) than indoors (white-collar) work, has been found to be a risk factor for development of lens opacities (e.g., Hayashi et al., 2003). There is also evidence of higher risk of age-related maculopathy for blue-collar compared to white-collar professions (Klein et al., 2001).
Eyeglasses are a potentially effective intervention for protecting against UV exposure and for accommodating to age-related changes in near-distance vision. An increase in computer-related work (e.g., Chan, Marshall, and Marshall, 2001, who reported 4–5 hours per day of computer work at a large corporation) means that instead of reading from paper sources people will increasingly be required to access information from computer monitors. Most monitors are placed about 40 to 60 cm from the user. This is a distance that, similar to vehicle instrument panels, falls between typical near-and far-focus distances and therefore leads to difficulty for older workers in their early forties and beyond. Potential solutions involve prescribing gradient lenses (progressive bifocals) and specialized lenses just for computer work. There are empirically validated ergonomic guidelines for the positioning of monitors, keyboards, and pointing devices (e.g., a computer mouse) that can minimize strain when working with these tools (e.g., Occupational Safety and Health Act, 2002). Whether these guidelines need to be modified to better accommodate older workers is not known.
For those working in the transportation sector, particularly those driving vehicles, age-related changes in vision and visual attention (e.g., shrinkage of the useful field of view, Owsley et al., 1991) can have a direct impact on safety and productivity. There are several studies demonstrating that signs can be redesigned to make them more visible, particularly by changing spatial frequency characteristics to improve contrast (Kline, Ghali, and Kline, 1990; Kline and Fuchs, 1993). There are many suggestions for