I don't know anything about glasses vs contacts as I only have glasses. I'm still trying to remember to try closing my eyes, or turning out the lights. I read from time to time that it's the thing to do. I have an especially hard time ignoring visual distraction at a dealer showroom, or at audio shows. I have noticed when I do close my eyes, I often lose track of where the midpoint is between my speakers, but it varies depending on the recording.

I usually listen at home daily. Haven't tried using time away as a palate cleanser, though I'm currently away on 10-day vacation, so I'll have to take note when I return.

Glasses have earpieces that can cause some reflection near the ear.

I always take mine off when listening if i can.

As commsysman said "glasses have earpieces". They cause a change in the sound. Glasses also change the acoustics associated with your head by their existence and position on your face. I take mine off when listening.

Do you find that a haircut makes a sonic difference too? 

Bill B wrote:

Do you find that a haircut makes a sonic difference too? 

I don't know , as I don't have any hair ( to speak of ) , but taking my specs off does seem to make a slight difference .

I rarely wear glasses but at this year's Rky Mtn Audiofest I tried listening to rooms with them on.  I found them a great distraction and I could hear the difference easily with them on versus off.  I tried it at home and will continue to not wear glasses while listening.  I suppose it may be what you are used to.  Bill B, I can also tell when I wear my dunce cap.   :-)