I realize this is an old post, but I found an even better way, and I don't see it mentioned anywhere. So, if your lenses are made of glass, the nail polish remover/acetone/alcohol way is all right. However if they're made of plastic, what you want to do is take a piece of leather, some toothpaste and polish off the letters. It will take some work, but the end result will be great, without any marks left.
If your glasses lenses are plastic, you can heat them and then you can remove the label easily. Or you can just put them in hot water for a while, then the label will get soft and you can remove it more easier.
Three simple steps can remove the logo on your non-prescription glasses lenses. 1. Wash and dry the lenses. 2. Dip a cotton swab in denatured alcohol. Allow any excess alcohol to drip off. 3. Apply the tip of the cotton swab to the logo on the lens, being careful to touch only the logo on the lens. Swirl the end of the swab in little circles. Repeat if necessary with new swabs until the logo is removed. Wash the lens with soapy water, rinse and dry.