Questions and answers
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Questions and answers
Some visual display users have reported sore and tired eyes, blurred vision
and eye fatigue after prolonged use of their terminals. It is natural for
some people to experience visual discomfort if they've been using their eyes
intensively over a long period of time, whether it is working at a display,
studying for an exam or doing close work. While eye fatigue may be uncomfortable,
it is not damaging to the eye. It also is a temporary condition and goes
away with rest.
Q. Does using a visual display terminal damage vision? How about
effects from long-term use?
A. Extensive research reveals no conclusive evidence linking VDTs
with any eye disease or damage. Studies have measured the vision of users
over several years and found no indication of visual impairment from long-term
use. However, some users may experience discomfort, such as tired eyes or
difficulty in focusing on faraway objects. This is temporary, and not harmful
to the eyes. A National Institute for Occupational Safety and Health (NIOSHA)
study stated that, "We did not find any significant association between
VDT use (including hours per week of VDT operation and total years of VDT
operating experience) and the prevalence of eye abnormalities, including
cataracts."
Q. Can working at a VDT cause eye discomfort?
A. Working at a VDT is similar to working at any other visually
intensive task, according to several scientific studies, and may result in
eye discomfort. The eyes may become fatigued while performing intensive tasks.
However, this condition is temporary and is not harmful to the eye.
Q. What causes some users to see pink spots or shaded areas after
using a visual display?
A. There are two phenomena that naturally occur in some individuals,
after-image and the McCollough Effect. The pink spots are an ""after-image" which
has been known for centuries, and disappear in seconds. The after-image actually
is the complementary color of what is on the screen. People see pink because
it is the complement to green, the common color of monochrome screens. The
McCollough effect produces the complementary color and pattern of the screen
and can last for several minutes. These phenomena are not unique to VDT use.
With increasing use of color displays, reports of these phenomena should
diminish.
Q. Is it advisable for VDT workers to have periodic eye exams?
A. Everyone's health program should include periodic eye exams,
especially when they are involved in visually intensive tasks. There is nothing
unique about VDTs that would require special eye care.
Q. Why do some people need a separate pair of glasses while doing
VDT work?
A. When eyeglass lenses are made to correct vision, they are made
to assist a particular activity such as reading or watching television. The
prescription for ordinary reading (short distance) may not be right for working
at a visual display terminal (further away). Also, the viewing angle is different.
People usually look down to read, but look straight ahead when using a VDT.
This means a different part of the eyeglass lens is used. Separate glasses
or bifocals are sometimes useful to compensate for these differences.
Q. What can be done to minimize visual discomfort?
A. Visual discomfort can be minimized and, in some cases eliminated,
by following some basic guidelines. First, everyone should ensure that their
eyes are properly corrected. VDT users should set up their workstations to
reduce glare and reflections from windows or overhead lights. They should
adjust the brightness control or contrast knob (on some displays) to a comfortable
setting and use a task light, if needed, for working with printed material.
Also, adjust the furniture and VDT position for a comfortable viewing distance
and angle plus easy access to the keyboard and other devices (e.g., a mouse).
As with any visually intensive task, display users should focus on a distant
object periodically and blink frequently.
Q. How important is proper lighting in minimizing visual discomfort?
A. Proper lighting is very important for any extended visual activity.
Proper ambient lighting and screen positioning will reduce reflections and
glare from lights and bright sources. Overhead lights can be designed to
direct the light and also may be dimmed to enhance screen contrast and reduce
glare.
To supplement office lighting, task lights may be used for reading from source
documents and written material. Daylight can be controlled through the use
of blinds or curtains to avoid glare.
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