Scratched sunglasses lens: what can be fixed, what cannot, and why toothpaste makes it worse

A scratch in a sunglasses lens cannot be repaired. A scratch is a groove where material has been removed, and nothing you rub on the lens puts it back. Every home remedy does one of two things: abrades the surface around the scratch until the groove is less visible, which on a coated lens strips the coating and leaves a hazy patch, or fills the groove with wax, which washes out in a day. The useful question is not how to fix a scratch but whether it matters, and that depends on where it is and how you use the pair.

What a scratch actually is

Lens surfaces are soft compared to sand, grit and metal. When a hard particle is dragged across the lens, it ploughs a groove. That groove scatters light, which is why you see it as a bright line against a dark background or a haze when you look through it.

Most modern sunglasses lenses are also layered: a hard coat for scratch resistance, sometimes an anti-reflective back, sometimes a mirror on the front, and in the case of laminated polarized lenses, the polarizing film inside. A scratch goes through those layers in order. A light scratch is in the hard coat. A deep one is into the lens.

What each "fix" really does

There is a version of the abrasive approach that works: on an uncoated glass lens, a professional can polish out a very shallow scratch. Almost no sunglasses lens is uncoated glass any more, so in practice this does not apply.

When a scratch matters

Position. A scratch at the edge of the lens or above your line of sight is cosmetic. One in the centre is in front of your pupil and you look through it all day.

Depth. Run a fingernail across it. If the nail does not catch, it is in the hard coat and mostly cosmetic. If it catches, it is into the lens and it scatters more light.

Use. For a pair worn for hours on water or the road, a central scratch is a source of glare and fatigue exactly where you need clarity. For a pair worn to the shops, it is a mark.

Polarization. In a laminated lens the polarizing film is sealed inside; a surface scratch does not affect it unless it goes through the outer layer. In a lens where polarization is a surface coating, a scratch through the coating leaves a spot that is not polarized. Our post on checking polarization shows how to test that.

Replace the lens or the pair?

For most sunglasses under about $60, a replacement lens costs more than the pair did, if it is available at all. At that price the honest answer is: if the scratch is central and the pair is one you wear a lot, replace the pair. Ours are $34; a scratched central lens on an T01 is a new pair, not a repair.

For expensive frames with replaceable lenses, the maker or an optician can fit new lenses, and that is worth it.

Preventing the next one

Almost every scratch comes from three habits, and all three are avoidable:

1. Wiping a dry lens. Rinse first, always. Our cleaning post is the full method.
2. Lens-down on a table. Fold them and put them lens-up, or in the case.
3. Loose in a bag or pocket. Keys and coins scratch. A soft pouch is enough; a hard case is better.

Frequently asked questions