Display Issues for Early 2011 Macbook Pro
This is almost certainly a hardware problem.  To determine whether it's the screen or the graphics card/motherboard you can plug in an external monitor.  If you get the same problem on the external monitor then it's likely a fault with the graphics card/motherboard, if you don't get the same issue on the external screen then there's a problem with your MacBook's display.  

Since it's an early 2011 model it should still be in warranty.  I'd bring it to an Apple store and have it checked out for repair or replacement.  On the plus side, you may get a brand new MacBook out of it.