Weird scratch like line in my iPhone 5 screen?

I didn't drop my phone, and I have an otter box anyway. I left it charging and freaked out when I saw this inch long line that starts from the bottom left corner and goes up diagonally. What's weird is you only see it on bright or light colors, and when you look at the screen at an angle. I can't see it when the phone is off, so there's no physical damage to the screen itself. It doesn't bother me enough to go spend bookoos of money to fix it but I just want to know what it is? I resell my phones every time I replace it when my contract ends, so just for that purpose I want to know.

Well I presume that the screen is damaged internally, in an otterbox it should have and physical damage. I would say there's a problem with the screen lights, go to Apple, if it's a manufacturing problem they should replace it under warranty.