COMPUTERS AND HEALTH part3

Light and glare

Eyestrain, headaches, and impaired vision are often a product of improper illumination resulting in glare, which is light within the field of vision that is brighter than other objects to which the eyes are adapted. Both direct glare from sunlight and lighting fixtures directed at the user's eyes and indirect glare due to reflections from video screens or glossy surfaces are common problems for VDT users.

Many offices are too bright for computer use, which may be a carryover from the days when paperwork required such brightness or the result of many office workers' preferences for sunlight and open windows. A NIOSH study recommends 200-500 lux for general office work; other sources suggest 500-700 lux for light characters on dark monitors and somewhat more for dark-on-light. If documents are not sufficiently illuminated, desk lights are recommended in preference to ceiling lights, which increase reflections from video screens. Reducing overhead lighting could also result in substantial energy savings.

VDT workstation placement is also important. Terminal screens should be positioned at right angles to windows, so sunlight is neither directly behind the monitor nor behind the operator, where it will reflect off the screen. If this is infeasible, blinds or drapes should be installed. Screens should also be positioned between rows of overhead fixtures, which can be fitted with baffles or parabolic louvers to project light downward rather than horizontally into the eyes or terminal screens.

Some users have found filters placed in front of the screen to be effective in reducing reflections, however some dimming or blurring of the display may result. Experts 1advise trial and error, since the best solution appears to depend upon specific conditions and user preferences. Finally, if you wear glasses or contact lenses, be sure your physician is aware of the amount of terminal work you do; special lenses are sometimes necessary. Bifocals, in particular, are not recommended for extensive terminal work, since the unnatural neck position compresses the cervical vertebrae.

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