Question of the day: do glasses or contacts slow vision loss?

I could find any answers on the internet, but I'm pretty sure that soft contacts and glasses don't. In fact if they're slightly too strong, I suspect they could make your vision worse. Know of any sites that support or refute this guess?

There are lots of slimy sites that will sell you exercises for your eyes - http://www.mercola.com/products/natural_vision_cd/index.htm for instance. Given the forced nature of all the pro-exercise websites and blog posts, I predict that they only improve their bottom lines.