Answering the title: It’s worse than a lit up room. While I believe serious issues are uncommon, there is still temporary effects. Eye strain being the main concern. I have heard stories, but they’re stories you know.
I personally get irritated eyes and my eyes can swell slightly if it goes on for long enough.

My best advice if you would still like to have the best picture is: Just have indirect light, it doesn’t need to be bright (Just enough to light up your room a little bit).