i had this same question, but then my little piece of dust went away. in the manual though it says to take off the eye cup and the rotate the eye peice counterclockwise and then blow in with a compressed air can.
its recommended NOT to use compressed air and instead use a blower from a lens cleaning kit. the compressed air sometimes lets out liquid and can ruin the interior coating in the VF. Dont use any lens cloth in there either.
