Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Hi, it's an old MacBook - it's definitely not under warranty. I'd like to know if anyone has ever seen this issue and what it could be - so I can see if fixing it is viable.

It doesn't look like dead pixels.
 
It's hard to know without looking if it's a problem with the display, the board, or a cable connecting the two. The cable is the most likely culprit. Your options are either to deal with it, or pay to have it fixed. There are many certified and non-certified repair options out there.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.