The screens of old CRT computer monitors often flicker. Whilst this flickering is not always evident to the naked eye, it can contribute to headaches and eyestrain. In fact, you may recall seeing past television footage of monitors flickering, whereas you will not see the same phenomena with LCD monitors. Indeed, new flat-panel monitors use different technology and avoid this problem altogether.
Screen flicker is mainly down to something called 'refresh rate'; you should not have a problem if the monitor you use has a rate of 60 Hz or above.
