Shorter Viewing Distance
With a conventional workstation, it's difficult to get the monitor far enough away to be beyond the horizontal resting point of vergence (about 45 inches on average), due to the depth of most work surfaces.
If we can't move the monitor farther away, lowering it has the same effect on our eyes. When we lower the gaze angle, we bring both resting points inward. That allows the same distance in inches to be less stressful.
Eye to Screen and Hard Copy Distances
For years, computer users were advised to place hard copy and the monitor at the same distance to reduce eye strain. A recent study found no basis for this recommendation. Jaschinski-Kruza (1990) found no increased eye strain when the distances differed between screen and document. In fact, users preferred the screen at a greater distance than the hard copy.