While it is physically 10cm from your eyes, there are collimating lenses, resulting in a picture that is apparently much further away from you, I think 1.3m is a typical distance, but it can vary by headset. It is much further away than a typical monitor. As for the light itself, it is light, no UV, not overly bright, sunlight is orders of magnitude brighter (which is a problem for AR btw). The image is also in front of you so no weird eye movement. I don't really see how it can damage your eyes though maybe some people know better, maybe the low resolution/screendoor effect can be a problem on current-gen headsets.

There are things that can cause strain. For example, items too close to you can be out of focus, the low FOV makes you move your head a lot more, and it has extra weight strapped to it, there is the heat, the motion, etc... But a well designed desktop setting like in the article avoids many of these problems.