Each day we spend a lot of time in front of a computer at work. The poor edge definition of the images on a computer screen can cause a repetitive refocusing effort for our eye muscles, leading to a variety of symptoms including blurred vision, headaches, or dry, irritated eyes as well as neck and back aches. Nearly 90 percent of those who use a computer at least three hours a day suffer from these symptoms, known collectively as computer eye strain.