Other than probably not tiny glasses just try some stuff out. Go to an optical shop, try stuff on. The general shape advice is actually too constricting, don't put much weight on it. If you don't know where to start, find a person whose style you like who is even vaguely shaped like you and look at what they wear. Could be an actor, public figure. Whatever. I use Robert Downey Jr as my personal shopper but you can find someone who resonates with you with some searching, I'm sure.
Go square. Lots of wiggle room depending on your personal style.
I'm betting something like the large squared off styles from Spy+ Optics would be a good starting place. Oakley, Costa, Sungod would have something along those lines as well. Personally I'd recommend Rōka and Kaenon most of all in that area.
For aviators you can go Caravan/Navigator styled Ray Bans, Randolphs, or Maui Jim depending on your budget. There's a lot that's north of there but... diminishing returns.
The Ray-Ban Clubmasters are going to work best… also the sunglasses that work best for me… not the most exciting/adventurous but they’re a classic for a reason. Because they suit all of us that don’t suit most sunglasses.
I think more rectangular over circular. Your face and beard give you a “circular” profile, so to give it more contrast, a more rectangular frame would be best!
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