Fixed My screen goes almost completely dark

In the main menu and in game my screen has gone almost completely dark , the characters are still visible and I still can control them and use the user interface but the screen is almost completely dark , I don’t know what to do . The problem doesn’t go away by turning off and then turning on the game or the computer .

I assume you only have this when playing d2r ?

Have you tried other games ?
Checked the vidéo settings in Settings > vidéo or display, don't remember which one is correct?
If you're on second screen, tried without it / if you're not tried with a second screen ?
Did it use to work and does not work now (then have you had any change) or did it never work ?
As Shadow said we most likely have not the answer but those questions should allow you to narrow down the issue.