I bought a pair of anti-fog eyeglass for swimming ,but to my surprise,there is still fog on the surface of the lenses when I reached the swimming pool.WHY ?

Anti-fog eyeglasses? Did you attracted by its ads? Tha's merchants' trick! I don't their are any anti-fog lenses, when cold lenses are put in a high temperature circumstance at a sudden, there must be fog on the lenses, it's just a phenomena of nature.

That' true, I have bought a pair of sunglasses with "golden coating", and I paid additional $60 for it, the optician said it can resistant fog of the lenses, but it was just normal tint of the lenses...