On some systems the setting advancedOpengl:true is still in the file options.txt despite the setting Advanced OpenGL is missing in the video settings and that setting is used ingame for AMD cards despite only useful for NVidia cards.
http://www.reddit.com/r/Minecraft/comments/1s5umw/minecraft_snapshot_13w49a/cduak3p

Steps to reproduce:

• Start Minecraft 1.6.4
• Switch Advanced OpenGL: On
• Quit 1.6.4
• Start Minecraft 14w25b
• No option is visible, but options.txt still shows as

  invertYMouse:false
  mouseSensitivity:0.5070422
  fov:-0.05
  gamma:0.5140845
  saturation:0.0
  renderDistance:12
  guiScale:0
  particles:0
  bobView:true
  anaglyph3d:false
  advancedOpengl:true
  maxFps:120
  fboEnable:true
  ...

This option is apparently still used in-game, because even users with AMD cards are having issues like MC-56897 and MC-56917.