DVD/CD lens cleaning discs.... do they work and how?

I see them all the time all over the place... but I don't understad how they would clean the lens on my players, and I don't thin there is any physical contact between the cleaner ad the lens...

If they do work, how often should I use them, and what brnads/types are recommended?

Thanks!

 

There's a tiny brush on the disc. Glides over the lens for 20 seconds.