Usually, instruction manual of the sunglasses will tell you if the sunglasses are wore by men, women or unisex for both men and women. If you fear to buy wrong sunglasses, you can further make sure it by asking the sellers. In fact, most of sunglasses have no limit for wearing by men or women. As long as you can good look from the sunglasses, you can wear it and show your personalities.
I think it is hard to tell whether the sunglasses are unisex or not. Nowadays, unisex sunglasses are very popular among people including both men and women. Actually, there is no limit that whether the sunglasses are suitable for men or women. As long as they can look good on you or can represent your personal style, both men and women can wear them. When I go to choose sunglasses, I don't care whether they are for men or women, I just try them on and see whether they are suitable for me. If they look great on me, I will get them.