Check the screen orientation regarding other light source.
Do not put your screen in front of a source of light (window) or with a source of light in the back reflecting into it.
Optimal orientation is with screen perpendicular to the window or light source to avoid reflections on the screen and light source behind the screen. Otherwise your eyes and brain will have to do allot of effort to focus on your screen.
Check also the screen quality. LCD flat screen are Ok. A long time ago I worked with a tube screen slightly out of focus and had terrible head ache by the end of the day even though I had no problem with my eyes. Changing screen solved the problem.
Optimal orientation is with screen perpendicular to the window or light source to avoid reflections on the screen and light source behind the screen. Otherwise your eyes and brain will have to do allot of effort to focus on your screen.
Check also the screen quality. LCD flat screen are Ok. A long time ago I worked with a tube screen slightly out of focus and had terrible head ache by the end of the day even though I had no problem with my eyes. Changing screen solved the problem.