eyes are designed to be stimulated by light and
to control the amount of light entering the eyeball.
There are, however, conditions which exist today
that are foreign to the natural lighting environment
and can cause an adverse reaction to light. The
largest single factor in the workplace is glare.
There are two general categories of glare: discomfort
glare and reflective glare. I will discuss discomfort
glare because it is the more common cause for
light sensitivity. Discomfort glare is largely
caused by large differences in brightness in the
field of view. It is much more desirable to eliminate
bright sources of light from the field of view
and strive to obtain a relatively even distribution
of light. You might be at greater risk to experience
discomfort glare when the source of glare is brighter
and when it is closer to the point of attention.
One of the primary reasons discomfort glare is
a problem for computer users is that light often
leaves the overhead fluorescent fixture in a wide
angle, resulting in light directly entering your
eyes. It is very common for the brightness of
the fixture to be more than 100 times greater
than that of the display screen that you are viewing.
This is a particular problem of computer workers
because they are looking horizontally in the room
(assuming the screen is at eye level).
Bright open windows pose the same risks as overhead
You are also at risk for discomfort glare if you
use a dark background display screen- resulting
in a greater brightness disparity between the
task and other objects in the room. Other sources
of large brightness disparity at the computer
workstation include white paper on the desk, light
colored desk surfaces, desk lamps directed toward
the eyes, or which illuminate the desk area too
highly. It is best if you keep all of the immediately
surrounding illuminations around the screen approximately