Figure 4-9. Your eyes make a drastic change in focus when shifting from the text
to the reflection on the screen. They have to adjust to include the
objects distance from the screen.
(10) Glasses. Video display terminal strain can be aggravated by glasses. If
you are only slightly nearsighted, and can see the monitor without your glasses, you
might suffer less fatigue by not wearing your glasses. Scratched or smudged glasses
will contribute to strain, as well as the added weight of glass lenses as compared to
plastic. Bifocal wearers have the biggest problems, as they have to contort the head
and neck in order to look through the bottom of the lenses in just the right way to see up
close. Consider getting bifocals that are a little higher than normal (at least 28
millimeters wide) to ensure ease of computer work. If you are having trouble seeing the
keyboard, computer screen, and copy clearly at the same time, you may need cathode-
ray tube (CRT) trifocals. These have an extra portion in the middle for intermediate
Figure 4-10. The height of your bifocals may be too low for comfortable computer
work. You may end up with neck strain as well as eyestrain.