Do you see your hand on the hand grips in a potion of the mirror??? wonder if my handle bars were installed to high??
Your mirrors should be adjusted so that you can view back and to the side (the lane next to you) on both sides.
In other words, if you're getting ready to change lanes, you should be able to see the lane behind you and to the left or right. And when riding in staggered formation you'd also then be able to see the face and eyes of the rider behind you and you could look into the mirror (left or right, depending on where you're at in the formation) of the bike in front of you and see that riders face/eyes. If they have their mirrors adjusted where they see directly behing theirself, then you'll not be able to see their face.
Are you short in the body? I am tall in the body and I was actually surprised at how well they worked without any obstruction (but then my head is up much higher than a short bodied person). While I'm 6'4", my wife is only 5'7" and she says that she doesn't have any problem with blockage in her mirrors.
However, I did replace them and went with handlebar mounted mirrors when I went with the tallker handlebars (HD Touring Pullbacks).