For those of us who work in computer sweat shops, where breaks are as rare as lumps of Dickensian coals, Eyes Relax, a free program for Windows PCs, will show you what you are missing.
After a quick and uncomplicated installation, you configure Eyes Relax for when you want to be reminded to move your eyes away from the computer screen and how you want to be reminded -- via dialogue box, picture, slide show or just a blank screen. There also are audio alerts that can be customized.
You can configure it for how long you want to wait between breaks, the length of time for the breaks, and whether you want to take short breaks in the midst of long breaks. And you can tell it to stop bugging you if you are in the midst of a major project. If you share a computer with someone on the lobster shift, each user can have his own profile.
The program can be password-protected so your sly supervisor can't tamper with your breaks.
Eyes Relax is a free download from http://themech.net/eyesrelax/. The programmers ask for a donation for their efforts.