Ask your eye doctor for a recommendation first, as some conditions will respond better to certain shades of glasses and levels of filters. Or if you have a low vision doctor, ask them.

I buy glasses from http://www.noir-medical.com/

The most relatively normal-looking frames that still cover a lot of your eye are the #52, #56, #200, and #35. I normally wear #35. If you can try them in person (doctor's office, store associated with a blindness organization, etc) you can see some of the filter colors and then order by phone if you need a different frame or style. The darkest lenses I believe they sell are 1% grey/green and 2% dark amber. They have several other colors at the 4% level. The percent is how much visible light is transmitted through the lenses (so the lower the number, the darker they are) so these are *very* dark relative to what you will find in commercial sunglasses.

I will say that when I started buying their glasses many years ago, they were *extremely* generous with helping me pick out a pair that fit my needs and returning pairs. I don't know what their official return policy is now.

If the noir frames don't wrap-around enough to protect your eyes, look at motorcycle or sport wrap-around sunglasses that have a foam gasket around them. These will have the tightest fit. Some frames will be able to accommodate the lenses being replaced if you need a darker than default lens.

You should get ones that have the top shields and the side shields as well. In Canada, the two that are reasonably priced are Noirs and Solar Shields. You want ones that provide 100% UV A and UV B protection, and dark enough to cut down the glare. Generally also avoid dollar store glasses.

Cocoons (http://cocoonseyewear.com/) are also a good brand, and fairly easy to get on-line. They also have a line of fitovers that can fit over prescription sunglasses, but it depends on your glasses (my own glasses have a very flat profile, and requires massive fitovers).