Jason over at Hackszine writes -
The lenses in my favorite pair of glasses are getting to be about a year or two old, and it’s getting to the point where I can barely see through them. My prescription hasn’t changed much – the problem is that the UV filter coating is starting to wear off, giving the entire lense surface a rough, partially-opaque finish.
I spent last evening trying to remove the coating and restore my lenses to a like-new condition, and I’m happy to say I can see again, thanks to a little polishing effort. You don’t want to do this if your glasses are in reasonable condition, but if you’re to the point where it’s between this and buying a new pair, it may be worth your while to give it a shot.
Sunscreen To The Rescue
It’s ironic, but I found that oil-free, SPF 45 sunscreen does a fantastic job at removing the thin coating from polycarbonate lenses. I believe this is because sunscreen has extremely fine aluminum powder in its composition, which is course enough to work away the coating, but fine enough to not leave visibly deep scratches in the soft plastic.
First, clean your glasses as best as you can. Using an old (but clean) sock or cotton rag, polish both sides of the lense, reapplying sunscreen as needed. You will feel the surface becoming noticably rougher as the coating is removed and becomes more patchy. It takes a long time, but eventually the last of the tiny patches of coating will be worked through and you’ll be left with a really smooth finish. As a last step, you should clean the lenses off and then polish them again with another clean rag.
It’s hard to photograph, but you can see the difference it made in my glasses (above). I haven’t yet tried, but this should also be a good way of removing the scratched up reflective coatings from cheap sunglasses. Your mileage may vary, so only try this as a last option, but let us know in the comments how it works out.