Dandy, your grasp of the obvious underwhelms me. Having worn eyeglasses in inclement weeather for over 16 years, I'm well aware of the fact that restricted air circulation induces fogging, with goggles, close-fitting shields, etc..
My post did not ask those who have not used the Grivel helmet/shield system to sarcastically shoot from the hip about its efficacy. I posted in order to get info from those who have used the system or have suggestions that might work.