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Monitors
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Monitor
Quick Tips |
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- Put monitor directly in
front of you and at least
20 inches away.
- Place monitor so top line
of screen is at or below eye
level.
- Place monitor perpendicular
to window.
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Choosing a suitable monitor and
placing it in an appropriate position helps reduce exposure
to forceful exertions,
awkward
postures, and overhead glare. This helps prevent possible health effects
such as excessive fatigue, eye strain, and neck and back
pain.
Consider the following issues to help improve your computer
workstation:
You should choose a monitor and
consider its placement in conjunction with other components
of the computer workstation, including the
keyboard,
desk,
and
chair.
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Potential
Hazards
- Monitors placed too close or too far away
may cause you to assume awkward body positions
that may lead to eyestrain.
- Viewing distances that are too
long can cause you to lean forward
and strain to see small text. This
can fatigue the eyes and place stress on
the torso because the backrest is no longer
providing support.
- Viewing distances that are too
short may cause your eyes to work
harder to focus (convergence problems) and
may require you to sit in awkward postures.
For instance, you may tilt your head backward
or push your chair away from the screen,
causing you to type with outstretched arms.
Figure 1.
Preferred viewing distance
is
20 to 40 inches
Figure 2.
Flat-panel displays take up less
room
than conventional monitors
Figure 3.
Corner units provide additional depth and
workspace
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Possible Solutions
- Sit at a comfortable distance from the monitor
where you can easily read all text with your
head and torso in an upright posture and your
back supported by your chair. Generally, the
preferred viewing distance is between 20 and
40 inches (50 and 100 cm) from the eye to the
front surface of the computer screen (Figure
1). Note: text size
may need to be increased for smaller monitors.
- Provide adequate desk space between the user
and the monitor (table
depth). If there is not enough desk space,
consider doing the following:
- Make more room for the back of the monitor
by pulling the desk away from the wall or
divider; or
- Provide a flat-panel display, which is
not as deep as a conventional monitor and
requires less desk space (Figure 2); or
- Place monitor in the corner of a work area. Corners often provide more
desk depth than a straight run of desk top.
- Move back and install an adjustable keyboard
tray to create a deeper working surface.
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Figure 4.
Place monitors directly
in front
of the user
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Potential
Hazard
- Working with your head and neck turned to
the side for a prolonged period loads neck muscles
unevenly and increases fatigue and pain.
Possible
Solutions
- Position your computer monitor directly in
front of you (Figure 4), so your head, neck
and torso face forward when viewing the screen.
Monitors should not be farther than 35 degrees
to the left or right.
- If you work primarily from printed material,
place the monitor slightly to the side and keep
the printed material directly in front. Keep
printed materials and monitors as close as possible
to each other.
Figure 5.
Display screen is too high |
Potential
Hazard
- A display screen that is too high (Figure
5) or low will cause you to work with your head,
neck, shoulders, and even your back in
awkward
postures. When the monitor is too high,
for example, you have to work with your head
and neck tilted back. Working in these awkward
postures for a prolonged period fatigues the
muscles that support the head.
Figure 6.
Comfortable viewing angle is
15 to 20 degrees
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Possible
Solutions
- The top of the monitor should be at or slightly
below eye level. The center of the computer
monitor should normally be located 15 to 20
degrees below horizontal eye level (Figure 6).
- The entire visual area of the display screen
should be located so the downward viewing angle
is never greater than 60 degrees when you are
in any of the four
reference
postures. In the reclining posture
the straight forward line of sight will not
be parallel with the floor, which may increase
the downward viewing angle. Using very large
monitors also may increase the angle.
- Remove some or all of the equipment (computer
case,
surge protector, etc.) on which the monitor
may be placed. Generally, placing the monitor
on top of the computer case will raise it too high for
all but the tallest users.
- Elevate your line of sight by raising your
chair. Be sure that you have adequate space
for your thighs under the desk and that your
feet are supported.
Figure 7.
Stresses because
of bifocal lenses |
Potential
Hazard
- Bifocal users typically view the monitor through
the bottom portion of their lenses. This causes
them to tilt the head backward to see a monitor
that may otherwise be appropriately placed.
As with a monitor that is too high, this can
fatigue muscles that support the head.
Possible
Solutions
- Lower the monitor (below recommendations for
non-bifocal users) so you can maintain appropriate
neck postures. You may need to tilt the monitor
screen up toward you.
- Raise the chair height until you can view
the monitor without tilting your head back.
You may have to raise the keyboard and use a
foot rest.
- Use a pair of single-vision lenses with a
focal length designed for computer work.
This will eliminate the need to look through
the bottom portion of the lens.
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Potential
Hazard
- Viewing the monitor for long periods of time
may cause eye fatigue and dryness. Users often
blink less while viewing the monitor.
Possible
Solutions
- Rest your eyes periodically by focusing on
objects that are farther away (for example,
a clock on a wall 20 feet away).
- Stop, look away, and blink at regular intervals
to moisten the eyes.
- Alternate duties with other non-computer tasks
such as filing, phone work, or customer interaction
to provide periods of rest for the eyes.
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Figure 8.
A monitor support that adjusts
the height and angle of the monitor
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Potential
Hazard
- Monitors that are tilted significantly either
toward or away from the operator may distort
objects on the screen, making them difficult
to read. Also, when the monitor is tilted back,
overhead lights may create glare on the screen.
This can result in eyestrain and sitting in
awkward postures to avoid eye glare.
Possible
Solutions
- Tilt the monitor so it is perpendicular to
your line of sight, usually by tilting the screen
no more than 10 to 20 degrees. This is most
easily done if the monitor has a riser/swivel
stand. A temporary solution involves tilting
the monitor back slightly by placing a book
under the front edge. Note:
Tilting the monitor back may create glare on
the screen from ceiling lighting and a glare
screen may be needed.
- Monitor support surfaces should allow the
user to modify viewing distances and tilt and
rotation angles.
Potential
Hazards
- Factors that reduce image quality make viewing
more difficult and may lead to eye strain. These
factors include
- electromagnetic fields caused by other electrical
equipment located near computer workstations,
which can result in display quality distortions;
and
- dust accumulation, which is accelerated
by magnetic fields associated with computer
monitors and can reduce contrast and degrade
viewing conditions.
Possible
Solutions
- Computer workstations should be isolated from
other equipment that may have electrostatic
potentials in excess of +/- 500 volts.
- Computer monitors should be periodically cleaned
and dusted.
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