Computer World. Матросова Т.А. - 80 стр.

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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 ref lections from
video screen 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 advise 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.
Breaks and exercises
Working in the same position for too long causes tension buildup and is thought
to increase the risk of repetitive motion injuries, such as carpal tunnel syndrome.
Remedies include changing postures frequently, performing other work interspersed
with computing (some studies recommend a 10-15 minute break from the keyboard
every hour), and doing exercises such as tightening and releasing fists and rotating
arms and hands to increase circulation. Be aware, also, that the extra stress created by
deadline pressure exacerbates the effects of long hours at the computer.
Radiation hazards
For at least a decade, concerns have been raised about possible effects of
radiation from video display terminals, including cancer and miscarriages. Earlier
fears about ionizing radiation, such as X rays, have been laid to rest, since these rays
are blocked by modern glass screens. Also well below exposure standards are
ultraviolet, infrared, and ultrasound radiation.

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