I have an iMac 27 inch running Yosemite 10.10.3.  Currently i have a 3 inch vertical band flickering on the screen.  Any help on fixing this would be appreciated.

I have a 27 inch imac late 2013 model running Yosemite 10.10.3.  Yesterday a 3 inch vertical band started flickering on the screen near the right hand side of the screen.   Is there any way to fix this?