As a photographer, you might not be able to ignore it. But see if connecting an external display this is still there. Also see if it is there no matter what program is running. Generally any large graphics anomalies can happen like this, because the lid is overstreched back, and the cable frays, spills, and drops, or power surge affecting the graphics chip. If an external display does not show it when you mirror the displays, then you know it is something to do with the communication to the display or the LCD itself. If an external display does show it when mirroring, then you know it has to do with the graphics chip. You can change graphics chip usage in Apple menu -> system preferences -> Energy Saver.
And check http://www.apple.com/support/exchange_repair/ if your machine is out of warranty to see if this is covered.