My Oakleys shook and wanted to suck off my face, so I bought a cord like the other fellows stated. Cut the cord off and stuck the rubber ends onto the glasses. Stopped the vibration and the glasses sucking away from my face.
On my 2011 RGU, I can wear any glasses and they don't move. I have the fairing lowers, engine guard baffles and stock windshield.
But I think your height, windshield height and glasses make alot of difference, although alot of wind will rise up from under the windshield, since that is a low pressure area caused by the shield itself.

 

The little ashtray thingie helped a little, but the air coming up from under the fairing by the blinkers on the outside of the fork legs is what causes my buffeting. Here's my solution:

 

It's the bike, time to trade...

 

Where you get those? how much, and do they have shiny ones?
Kroozeabout.

 

I got them on eBay from user id: timelessmotorcycleparts

I got them for $80 or so IIRC, but they were copper color. I had to have them powdercoated. I think I'm going to buy another set and trim them up so they do not block so much wind from the motor. The change in airflow is noticeable on your thighs. They get warm from time to time.

I'll attach this link, but I don't know how long it will last before it's removed:

http://cgi.ebay.com/ebaymotors/HARLE...Q5fAccessories

 

I had the same thing on my roadking. Try Laminar Lip it cured all of the turbulance on my bike.

 

+1 on that

 

I have Oakley Tightrope holds great

 

I put fork mounted wind deflectors on for long trips. Works great. Test where wind is coming from first. When riding, place your left arm and hand across your chest like a salute. This breaks the wind coming from below.

 

I used to have this problem (glasses sliding down a lot) when wearing a half helmet with the visor installed. I removed the visor, and a lot of the turbulence under the visor disappeared, and had no more issues with my glasses moving. The height of the windshield also matters.

Goggles is also a good option. I have some HD goggles and some from Bobster - both work great.