The "OPTIMAL" anti-fogging is made up of a double ventilated lens with an internal treatment and an air vent on the frame that ventilates the inside of the ski goggles.
For good ventilation inside your goggles, do not obstruct these air vents with a neck warmer, for example.
Do not rub inner surface of lens but dab it carefully in order to preserve the anti-fogging treatment for as long as possible.