Yes, staring at a computer screen for a long time is bad for eyes. First, the computer screen releases radiation that is bad for the eyes. Second, the heat from the computer screen can increase the evaporation of water in air around you that cause dry eyes. Third, staring at computer screen can easy cause eye strain. If you are addicted to stare at the computer screen, focusing computer screen for a long time is easy to cause pseudomyopia that may possible develop to myopia.
There is no doubt that computers can do a lot of harm to your eye health. When you sit in front of the computer for a long time, your eye muscles will be very sore and along with this symptom are neck pain, blurry vision and sometimes even a headache. Well, I think you may already have experienced these symptoms. Of all these symptoms, I think the most insufferable thing should be eye strain. Nowadays, eye strain is so common. If your work requires you to spend most of your time to sit in front of your computer, then I strongly suggest you to rest your eyes every an hour, even only for 10 min will be very helpful to your eyes.