Yohan, I have just ordered a pair of sports prescription glasses from optilab - photochromic varifocals which are are virtually clear in the dark so safe to use at night. Their prices are on their website
http://www.optilabs.com. I have just paid £168 for mine and considering how much my normal glasses cost this seems a bargain to me. I haven't paid for them yet, so I might quiz them about the 10% discount Ajay mentioned. They are open 'till 4pm Saturday, and 8pm Monday and they do normal designer glasses too.