I think the sunglasses with light material is suitable for you who is with low nose bridge. If it is too heavy, it may come down. Thus the plastic sunglasses are the most suitable ones for you. What's more, the big frame sunglasses is not suitable for you, too, which may make your nose look small. You'd better buy the sunglasses with third dimension which may show your nose look supported.
As a person of low nose bridge, you would better find sunglasses with nose pad, and the glasses itself must be edged, as low nose bridge usually lack of it, the glasses will be a kind of make up for them. It would be fashion, and then the decorations in the glasses will shift the attention from your nose to the fancy patterns. The frame must be suitable for your face shape; the exaggerated ones will not suit you. You can refer to lady gaga, the frame would be smaller than her, and the color would be lighter than her. The color must be match for your skin, it will be perfect.
Hello, you may have a try on wearing these sunglasses suggested for you. First I think some raybans are ok, so are some pradas. They're all wire style. Besides those, some asian people like wearing IMO, the old skool ray bans, which may also be a choice. So just think about them and choose the one that suits you best.