If you use the Kickoff menu style, the icon will shrink with a very tiny amount for a fraction of a second when you click it.
If you use the default classic menu style, it will remain a wee bit smaller for as long as the menu is open. Is it then distorted? If I look at it through a magnifying glass: yes. Not so much that I'd normally notice it, but yes.
Well spotted asdfchanta. And congratulations on your eyesight.