I believe that is the lens of the eye. This will present better as part of the design on an otherwise better strike.
As the dies wear out, elements of the design will also wear and additional die polishing reduces and/or eliminates parts of the design. Compare reverses also. You will see things on the memorial that look like doubling but are actual parts of the design that you cannot see on a poorly struck coin. The insides of the bays come to mind. The pillars will show what looks like doubling because you cannot always see it on a poorly struck coin.
I see what you are referring to, and it doesn't seem to appear on other cents, but I don't believe it is anything more than possibly a plating issue. I hope others chime in with their thoughts.
