I noticed this issue from the initial 2011 release of Autocad for Mac: when you pan in horizontal with a few of lines the transition is "pixelate" showing glitches and artifacts along the lines (worst with complex drawings). Nothing appears when you use the vertical pan. This behavior is running Autocad 2015 under Yosemite 10.3.3 (but was the still under Mavericks and with previous releases of AutoCad for Mac) and using Magic mouse. Reading everywhere someone refers the problem to Vsync (trying to disable through apple developer tools), or Nvidea graphic incompatibility drivers (depending by Apple) and others look at the use of magic mouse try to solve with microsoft mouses and traditional wheel to pan. Anyway this issue is still live and without solution...
