It was recommended to me much earlier that good ambient daylight-like lighting improves productivity and reduces stress on the eyes. The latter is because bright screens only in an otherwise comparatively dark room stresses the eyes when switching or adjusting between screen and background.

What was the argument for the former? The latter makes no sense to me. If you only have bright light, then you're only stressing the sphincter of the iris. If you switch between brightnesses, also the dilator gets work and the sphincter gets to relax for a while.

These of course depend on how bright or dark we're talking about.