A patch has been released on Steam to fix issues with AMD hardware, and improve performance for these cards. It's live now, but might take a few minutes to reach everyone. Restart your client or verify local files if it doesn't download automatically.
It also fixes a shadow visual corruption bug on AMD 7xxx cards, and fixes an issue with the game starting only in 3:1 resolution on some TVs.
In addition, you can now customize the FOV this way:
After starting the game up, the user.cfg will be updated with the r_base_fov attribute. You can find this in %LOCALAPPDATA%\4A Games\Metro LL\. Tweak it at your leisure!