For me, it's probably something along the lines of this (from S6's "All The Way"):
Buffy : Is that why you're always cleaning your glasses? So you don't have to see what we're doing?I've worn glasses for years now, and for the life of me, I can't keep them clean from minute to minute. I must have at least 20 of those microfiber glasses cleaners stashed in every conceivable place: living room, bathroom, office, car, briefcase, kitchen. And it seems that I'm pulling one of those out to wipe them down every 10 minutes. I should probably go to Sam's Club and buy the lens cleaner in 55 gallon drums. I have no idea where all the glasses schmutz comes from. It's not like I compulsively decide to poke myself in the eye, with only the lens to protect me from becoming a cyclops. (Or Xander in S7!) I always take them off and put them on by the frame. I don't spray when I talk like Lou Holtz or Bill Cowher. I don't use them as protection when I'm dissecting corpses in the crime lab. I don't run out onto the balcony and stare at the sky during heavy precipitation. Yet I constantly see some type of smudge or particle on the lens that bugs the fuck out of me and I have to wipe it off.
Giles : Tell no one.
I'm probably one psychotic break away from purchasing these: