HP Compaq Presario,Presario 1515 Supplementary Manual page 19

Keep your display screen and your eyeglasses or contact lenses clean. If you use a
glare-reduction filter, clean it according to the manufacturer's directions.
To be sure that your vision is adequately corrected, have your eyes examined
regularly by a vision care specialist. Consider having glasses made that are
specifically suited for working with a computer monitor. If you wear bifocals or
trifocals, you may find these special monofocal glasses more comfortable for
computer use. For more information, see Adjusting monitor height for bifocal and
trifocal users on page 12.
J
You may find a range of monitor heights that allows your head to be balanced
comfortably over your shoulders.
You will reduce eye strain and muscle fatigue in your neck, shoulders, and upper
back by properly positioning your monitor and adjusting its angle.