Thats been tested and its not it. The leading hypotheses a few years back is that the outdoors is very bright. Brightness levels that cannot be easily reached

Thats been tested and its not it. The leading hypotheses a few years back is that the outdoors is very bright. Brightness levels that cannot be easily reached indoors. surely when we squint from bright light we are straining the eye. The idea, then, is that our development expects some amount of eye strain growing up.