For those of you who don't have to wear glasses you don't know how lucky you are - seriously. I've attempted to play with glasses, and I have finally given up. I wear a Proteus, and it was an ok fit with my glasses. Problem was when I moved my head fast (snap shooting, quick looks, etc), the sides of my glasses would "tap" the lens. After a day of playing, I had scratches on both sides inside my lens! I switched to another pair of glasses that were smaller, and didn't have the problem any more (although the damage was done). So, make sure you can jerk your head around without tapping the inside of your lens.
However, in this paintballers humble opinion, playing with glasses absolutely sucks. You can try to use the anti-fog stuff, and it works for a while. However, you can't use it on glasses that have the anti-reflective coating, otherwise the AR coating will dissapear, FYI. Another thing I found was that when I first put on my goggles, and had the anti-fog spray on my glasses, no problems. It worked well. However, if you happen to have extended play (more than one game basically), I did either fog or somehow manage to get sweat to drip on my glasses, which screwed up my vision immensely. What's the use having anti-fog gogs when you're pretty much screwed wearing glasses?
So, I made the switch to contacts. I know they seem expensive, but really it's a good investment. Just get your prescription, go to 1800contacts.com or somewhere like that, and get some cheap disposable contacts. I only use them for paintball, so the "30 day use" contacts will last me for 30 days of paintballing (unless I wear them for other reasons, which I don't). The cleaning/storage solution stuff is pretty cheap (get generic brand stuff), and there you go, you're all set.
I played with contacts for my first time recently, and I can't even begin to tell you how much better it was. It's SO worth it. I will always bring by glasses to the field as a back-up, but I doubt I'll ever wear them again in play.
That's my experience - hopefully you can benefit from it.
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