CD lense cleaner. Is it necessary ?

I'm wondering if my cd player may need the optical lense cleanded as it is a used player. I've seen the basic cleaning discs such as the ones in Radio Shack and other electronic box stores. Is this procedure really necessary? If so how often? and which process/brands of cleaning devices really work? Again, it is the optical lense in the player's transport that i'm looking to clean. Thanks.