I have had a late 2013 retina macbook pro since Oct of last year, bought it off a seller with good rep from ebay, with apple warranty until Nov 2014. Recently, I have seen this very faint sort of vertical dark blotch or streak on my screen, it is sort of to my lower right about 2 inches long. I see it while there is just white or mostly white on my screen and I look at it from a side angle, not as much head on. I may be just imagining it, since it has taken me this long to see anything, the last day or two, I would look, and it seems ok, other times it seemed something was there. Am not sure quite what to do, I will keep an eye on it if it gets worse, maybe I just need to clean the screen, but am not sure how to do that safely. Is there any kind of test or tests I can run to check the integrity of the screen? I googled this, and there is some mentioning of LG vs Samsung screens, don't how to check this on mine.