For an everyday pair, colour matters more than shape. Tortoiseshell is the most forgiving because the pattern breaks up the frame against your face, black is the most graphic and the least flattering in strong sun, and clear or metal disappears entirely, which is either the point or the problem. Shape is worth less agonising than the internet suggests: if the frame is roughly as wide as your face and the top line sits under your brow, it works. Below, the tortoiseshell, the black frames, and the clear, cream and metal. The measurement worth knowing is the frame width against your own. A frame noticeably wider than your face slides down your nose all day; one narrower makes your face look wider by comparison. Everything else is preference.

Tortoiseshell is where I would spend the money, because it goes with everything and hides scratches. Look for a pattern with real variation in it rather than a flat printed brown. Look for depth in the pattern rather than a flat printed brown, which is the tell of a cheap acetate. Real tortoise effect acetate has variation through the thickness of the material, so the pattern shifts as the light moves, and it hides the small scratches that any pair collects within a month. It is also the most forgiving colour against warm and cool skin alike.

Black frames are the strongest option, and the one that most needs to fit properly. A black frame that is slightly too wide reads as borrowed, where a tortoise one gets away with it. Black is the strongest and least forgiving choice, which means fit does more work here than anywhere else. A black frame slightly too large reads as borrowed; slightly too small reads as severe. If you wear a lot of black, a black frame disappears into the outfit, and that is either the point or a reason to choose something else.

Clear, cream and metal frames are the quiet choice. They photograph better than black and they suit warm skin tones in a way that a hard black rarely does. Clear, cream and metal frames are the quiet option and the most flattering in photographs, because they let your face rather than the frame carry the picture. Metal is worth considering for durability: a wire frame can be bent back into shape indefinitely where acetate cracks, though it is less comfortable in cold weather.

Quay has the deepest range at this price and it is the easiest place to try a shape you are not sure about without committing real money. Their polarised options are the ones worth paying up for. The range is deep enough to try a shape you are unsure about without spending real money, which makes it the sensible place to work out what suits you before buying something expensive. The polarised versions are worth the small premium if you drive or spend time on water.

A few more, across brands, if you would rather just see the whole spread. A wider spread to finish, across brands and shapes, for when you would rather see everything at once. Prices here run from very reasonable to properly considered, which is useful if you are deciding whether a second pair is worth it.

Two things that actually determine whether a pair survives the year. First, buy the case and use it, because scratches come from bags, not from wear. Second, check the hinges rather than the lenses: a metal hinge set into the acetate will outlast a plastic one by years, and it is the part that fails first. If a pair slides down your nose, an optician will adjust the arms in two minutes, usually for nothing.