Correct lighting arrangements are essential if eye fatigue is to be avoided. Suitable background lighting is required for DSE work to provide an appropriate contrast between the screen and the background environment and to avoid problems of reflection and glare.
Generally, you don’t want a monitor facing to window to reduce glare or a window at the rear of the screen forcing the eyes to adjust to two different light sources. If windows are present, they should be perpendicular to the screen.
It is good practice to adjust the contrast if needed is brightness levels are affected by changes from very sunny to dull.