In setting up software, choose options giving text that is large enough to read easily on your screen, when you are sitting in a normal, comfortable working position. Individual characters on the screen should be sharply focused and should not flicker or move. If they do, the VDU may need servicing or adjustment. Posture and breaks Don't sit in the same position for long periods. Make sure you change your posture as often as practicable.
Most jobs provide opportunities to take a break from the screen, e.g. to do filing or photocopying.
Frequent short breaks are better than fewer long ones.