I had mine replaced a while ago, and there was, from the git-go, a "halo" where the light entered/exited the polycarbonate. Lexan is not as clear as air and will diffract some amount of light. Hence the halo. If there are "sparkles" inside the halo, those would be pitting. Even if you can't feel them, an imperfection as small as 1 Angstrom is visible. The only way to be rid of them is to remove the surrounding polycarbonate down to the level of the bottom of the imperfection.

Just like swirl marks in paint.