Make sure that you have updated graphics card drivers
Because Amnesia uses OpenGL, your graphics card may not support the minimum version required or your drivers may be outdated even though you can run most other games (which use Direct3D). In order to learn more visit the Graphics Card Troubleshooting Guide.
Note: This is the proper fix for upside-down graphics as well for the black screen issue that Intel HD cards experience.
Make sure the game is updated
Turn off post effects
Go to Options > Graphics > Advanced and here you can turn on/off all of the different effects in the game. No restart of the game is needed for these changes, so simple go back to game and see if it has been fixed.
Reset game settings
Sometimes changes you have made can cause problems with the game. In order to fix this you need to reset the game's settings. Go to the game's save directory and remove the main_settings.cfg file. Then start the game from the launcher without changing anything. If all works, you can exit the game and carefully change a few settings at a time. The save directories are mentioned below.
Amnesia: The Dark Descent:
- Windows XP, Vista, 7 & 8.x: Documents/Amnesia/Main/
- Linux: .frictionalgames/Amnesia/Main/
- Mac OS X: ~/Library/Application Support/Frictional Games/Amnesia/Main/
Amnesia: A Machine for Pigs:
- Windows XP, Vista, 7 & 8.x: Documents/Amnesia/Pig/
- Linux: .frictionalgames/Amnesia/Pig/
- Mac OS X: ~/Library/Application Support/Frictional Games/Amnesia/Pig/
- Mac OS X >= 10.7 (App Store): ~/Library/Containers/com.frictionalgames.AMFPLauncher/Data/Library/Application Support/Frictional Games/Amnesia/Pig/