Make the following adjustments to your working environment with your monitor turned off:
Adjust ambient light
Establish a suitable surround
Establish a comfortable viewing distance
You do not need to shut down your computer as long as your monitor has its own power switch.
Your screen has a glass faceplate that reflects--into your eyes--light that originates behind you. Reflections can change your perception of your display at the location where it is reflected. The flatter your monitor's faceplate, the less of a problem reflections are likely to be; a highly curved screen "collects" reflections over a wide angle behind you.
To determine whether your screen has reflections, sit in your normal working position and examine the dark screen for reflections. (The reflections may be distorted by the curvature of the screen.) Try to arrange your environment so that no intense light sources are reflected on your screen. If you cannot move your furniture, either move the light source or block your (reflected) view of the offending object with dark cardboard baffles.
Your monitor's screen may have an integral antiglare coating or treatment to minimize glare. A monitor with this treatment appears to have a very dark screen when it is turned off. You can attach an external antiglare screen to the front of your monitor, but some antiglare screens have such low light transmission that you may find that they reduce the intensity of white to an unacceptably low level.
Not only can you see light that originates behind you, but you can see objects other than light, like your own silhouette. To minimize reflections of objects in front of your screen other than lights, reduce the general light level, or ambient illumination. Overhead fluorescent light is usually the cause of this type of reflection because it is excessively bright. Use a different light source (for example, lamps) if this type of reflection occurs.
Visual stress is induced if--while watching your screen--your peripheral vision is exposed to a light intensity substantially brighter than the brightest regions of your display. The color science term surround refers to the area perceived by your peripheral vision while you are looking at a display. In addition to disturbing your peripheral vision, a bright surround increases your ambient illumination. Try to establish a visual surround that is darker than the brightest white of your screen.
It is beneficial to have a visual reference to the outside world--such as a window to the outdoors--while working at your computer. If you have a window, make sure you sit so that the window is far enough to your side that it does not impinge your peripheral vision, but not so far behind to reflect in your screen.
If you can see individual pixels on your screen, you are probably sitting too close to your screen. Visual recognition skills, particularly reading, develop on the basis of recognizing shapes, not dots. When you look at the letter "V", you should perceive two angled intersecting straight lines, not two jagged vertical elements or a collection of dots.
For minimum stress viewing of your screen, you should work at a sufficient distance so that you cannot see individual pixels on the screen. A sufficient distance is usually at arm's length. Extend your arms in front of you while you are sitting at your workstation. The tips of your fingers should reach the faceplate of your screen. The arm's-length viewing distance minimizes stress due to focusing at short distances for an extended period of time.