There are a few things that you can do to keep your glasses and goggles clean. It might not work all the time, but try it because it works with some applications. If your lenses fog up or get dirty from dirt. Next time, try one of these.
To keep dirt off:
Put clean liquid soap on the lenses, a very thin clear film. This will keep the dirt off.
Anti fog cream or spray. It will probably work for up to an hour or so.
Clean them as often as you can, without scratching them. Also, clean them occassionally with alcohol. Rubbing alcohol and NOT vodka :)
Get lenses withOUT anti-reflection coating. The A/R coating attracts dust and makes it hard to clean. Also, keep them clean and free of oils and sweat.