Andy...I too already have a pair of prescription glasses....it took a long time to a pair that I liked....here are some features to keep in mind:
- frame design options with a more flattened front for those of us with heavy prescriptions....the wrap around styles cause vision distortion somewhere in the viewing area due to the significant bend;
- definitely side pieces for the "squared frame"..preferrably with a tinted plastic lenses on the sides for perriferal vision....side pieces block out both back glare and wind...I fish saltwater and the wind can really dry out the eyes;
- I like the sweat band topping previously mentioned, if it can be incorporated behind the frame.....we look enough like dorks in our waders, no need to have an obvious sweat band :-)
- the option for interchangeable lenses (ie. for different colors);
- stainless steel frame screws, esp. for us saltwater guys;
- shatter proof lenses
- non reflective finishes on the frames....don't want to scare the fish;
- while I'm at it...an anti fog coating or compound/spray that really works.
Now.....you get all this, then I would be happy to field test a courtesy pair :-)
Good luck Andy...I'm sure that others will chime in with their ideas.
PS: some of the above features would also be of interest to bikers/hikers