O.K. all of what everyone has said so far is good advise and for the most part I've been there, done that, so here are a few extra comments of my own.
I am farsighted which means that my glasses are thick in the center, thin around the edges. Fit overs always scratched my regular poly carb glasses right in the sweet part. Besides the quality was not near as good. As I wear progressive bifocals, this became very expensive to have to replace the lenses. Oversize, tinted, scratch resistant, yada, yada, yada.
Inquiring about prescription polarized shades I was told that they would be thicker and heavier than what I was wearing. This was not acceptable. What were my options?
At the time there were not too many. One was contact lenses. Bifocal contacts? No, they do not work very well. However I was able to wear contacts to correct distance vision. This resulted in a big weight reduction in my glasses since they now only had to corrrect for close up work. They were still progressive bifocals and still very expensive but since the upper part is zero prescription, much thinner, and lighter weight. Life is good.
I also found that my vision was much improved. I had to wear a tool makers eye loupe that I would flip down when I had to tie on small trout flies. Don't have to use the toolmakers loupe anymore, even with # 20 flies.
The contacts worked well unless I put in a looooong day. Then they would get kind of gummy and no amount of eye drops would bring them back. I would have to resort to wearing my old glasses if I wanted to stay up and be able to read. The only other reservation I had with the contacts was that I had to keep buying replacements every 90 days. ( I was wearing the disposables. I could get about a week out of a pair of lenses)
Although laser eye surgery had been available for a while, it had only been perfected for near sightedness. (it won't work for you, the story of my life it seemed) No more. Wonder of wonders, they have now perfected the technique to correct for not only far sightedness but astigmatism as well! After checking this out and consulting with my optometrist, I decided to have it done.
The results are truely amazing! I can see very well without any glasses at all. I still use my expensive progressive bifocals but I really only need them for fussy close up stuff like tying flies etc.
I too am still searching for solutions for good polarized fishing glasses or I wouldn't have checked out this post. But the bottom line is this. They no longer have to be pescription glasses, therefor they don't have to cost an arm and a leg and they don't have to come from your optometrist. There are several options for taking care of the close up work. And remember that we are only talking about fishing glasses, not every day full time glasses.
With that in mind consider the following options for taking care of close up work such as tying on #20 flies. Flip focals, these are cheap. clip onto the bill of your hat and you don't have to remove your sunglasses to use them. Stick on bifocal lenses, these are also enexpensive and adhere to the back side of your sunglasses. They are not as cool as progressives, but they are only for temporary use, when you are fishing. As a last resort, you could go down to the local drug store and get some reading glasses. Wear them around your neck on a corkie. You would have to remove your polariods ( also on a corkie) to use the reading glasses but it would enable you to see up close. All of these are kind of a pain in the butt and not near as good as polarized progressives, but they will work for a temporary solution while out fishing.
The good polarized sunglasses really do perform better. They will block out UV better, will cut glare better, and will not distort the way the cheapies will. I have been looking at various options for quite a while now and am currently investigating glasses with interchangable lenses, different shades for different applications. Like the wrap around styles but haven't really settled on anything yet.