Sunglasses buying guide: UV protection, polarization and fit

2 min read · Updated 2026-10-26

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What UV400 and polarized mean, why lens colour does not show protection, and how to choose the right frame size.

Sunglasses protect your eyes as well as looking good, but dark lenses alone do not guarantee protection. These are the points that matter.

UV protection first

Look for UV400, which means the lenses block light up to 400 nanometres, covering UVA and UVB. Dark lenses without UV protection are worse than none, because the pupil opens wider and lets in more harmful light. Cheap sunglasses sometimes claim UV400 without proof, so prefer sellers with many reviews.

Polarized lenses

Polarized lenses cut glare from water, roads and snow, which makes driving and fishing more comfortable. Polarization is separate from UV protection, so check for both. A simple test is to look at a phone screen through the lens and rotate it; polarized lenses make the screen go dark at some angles.

Lens colour and tint

Grey lenses keep colours natural, brown increases contrast, and yellow can help in low light. Colour and darkness say nothing about UV protection.

Lens material

Polycarbonate lenses are light and impact resistant. Glass is clearer and scratch resistant but heavier and more fragile. Resin and acetate frames and lenses vary in quality.

Frame size

Three numbers describe a frame: lens width, bridge width and temple length, all in millimetres, for example 52-18-140. Compare them with a pair you own that fits well.

Fit and comfort

Frames should sit comfortably without pinching behind the ears or sliding down the nose. Nose pads that can be adjusted help. Larger frames cover more of the eye area and give better protection.

Cases and care

Use a case and clean lenses with a microfibre cloth. Rubbing them dry with clothing can scratch the coating.

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