First of all happy Holiday! I was lucky to get a 5s. Now I have notice that on the left edge there is a small very faint area that is lighter than the rest of the screen. I used to have exactly the same issue with an iPod touch a couple of years ago. You can spot it best when you scroll vertically, e.g. In the photos app. Can you please check whether your iphone had that, too, and report? Thank you!!