The cheapest way to fix this is verify your overhead display lighting isn't of a different frequency than the display itself. Sometimes the two lights may be out of sync, and what you are seeing is the overscan effect in the lighting of the room.
The next cheapest way to fix this is to connect an external display and use that instead. That is unless you purchase AppleCare Plus and are still under its coverage.
Display anomalies like this may be due to fraying of display cables connecting the display to the computer screen through the hinge. Overextending the display hinge can lead to such fraying. When you feel resistence, don't go beyond the point you start feeling resistence in opening the display hinge. Spills, drops, bumps can all trigger such display anomalies.
Call AppleCare if you have such coverage, and also see if you are under one of the extended service plans:
Apple Service Programs - Apple Support