Apple PowerBook (3400 series) - Manual (Page 139)

Eye fatigue
Eye fatigue can occur whenever the eyes are focused on a nearby object for a
long time. This problem occurs because the eye muscles must work harder to
view an object that’s closer than about 20 feet (6 meters). Improper lighting
can hasten the development of eye fatigue. Although eye fatigue is annoying,
there’s no evidence that it leads to permanent damage.
Whenever you’re engaged in an activity that involves close-up work—such as
reading a magazine, doing craft work, or using a computer—be sure to have
sufficient glare-free lighting and give your eyes frequent rest breaks by
looking up and focusing on distant objects. Remember to have your eyes
examined regularly.
To prevent discomfort and eye fatigue:
m Arrange your work space so that the furniture is properly adjusted for you
and doesn’t contribute to an awkward working posture.
m Take frequent short breaks to give your muscles and eyes a chance to rest.
Arranging your work area and equipment
The suggestions in this section can help you work more comfortably with
your computer.
Chair
m An adjustable chair that provides firm, comfortable support is best. Adjust
the height of the chair so your thighs are horizontal and your feet flat on
the floor.
The back of the chair should support your lower back (lumbar region).
Follow the manufacturer’s instructions for adjusting the backrest to fit your
body properly.
139 Health, Safety, and Maintenance Tips