Quick Answer: Almost all lens damage is dry-wiping abrasion. Salt, sand, and dust sit on the lens; a cloth drags them across the surface and they cut fine scratches into the coatings. The correct method is: rinse under lukewarm water first, add a drop of plain washing-up liquid, rinse again, then dry with a clean microfibre cloth. Never dry-wipe, never use a shirt, and never use alcohol, ammonia, or window cleaner - those strip the anti-reflective, hydrophobic, and anti-fog coatings that you paid for.

Here is the method and the specific things that kill each coating.

Why does dry-wiping cause so much damage?

Whatever is on the lens becomes the abrasive. Sports lenses collect salt crystals from sweat, road grit, dust, and sand - all harder than the coatings - and a cloth simply drags them back and forth.

Coatings are thin and soft. Anti-reflective and hydrophobic layers are measured in nanometres. They scratch far more easily than the lens substrate underneath, which is why the damage looks like haze rather than obvious gouges.

Sweat is the specific problem in sport. As it dries, salt crystallises on the lens surface. Wiping dried salt is the most common single cause of scratched sports lenses, and it happens mid-session, when there is no water available.

Shirts and jerseys are worse than they look. Technical fabrics hold grit, and their weave is coarse compared with microfibre. A jersey is effectively fine sandpaper carrying whatever the day has deposited on it.

And the damage is cumulative and invisible at first. Each wipe adds fine scratches, and it takes weeks before the haze becomes noticeable - so people rarely connect the cleaning habit with the outcome.

What is the correct method?

Rinse under lukewarm running water first, always. This removes the abrasive particles before anything touches the lens. It is the single most important step and it takes ten seconds.

Not hot water. Heat can damage coatings and, on some frames, soften the lens or loosen adhesive. Lukewarm is the instruction and it matters.

One drop of plain washing-up liquid, rubbed gently with your fingertips. Not a scrub - fingertips are softer than any cloth and a drop of dish soap is a genuinely recommended lens cleaner.

Rinse thoroughly. Residue leaves streaks and attracts dust. Rinse longer than feels necessary.

Dry with a clean microfibre cloth, patting rather than rubbing. Or air dry - air drying is the safest option of all and perfectly adequate.

And wash the microfibre cloth regularly. A cloth used for weeks carries embedded grit and becomes the thing doing the damage. Machine wash without fabric softener - softener coats the fibres and leaves smears.

What should never touch them?

Alcohol, in any form. Isopropyl, hand sanitiser, alcohol wipes. These strip anti-reflective and hydrophobic coatings and are the fastest way to ruin a good lens.

Ammonia and window cleaner. Glass cleaner is formulated for uncoated glass and destroys lens coatings. This is the most common well-intentioned mistake.

Acetone and any solvent. Obviously damaging to plastics, and it will fog or craze a polycarbonate lens permanently.

Paper - tissue, kitchen roll, napkins. Wood fibre is abrasive at this scale. Paper towel is far rougher than it feels on a coated surface.

Anything abrasive at all - toothpaste, baking soda, polishing compounds. The various internet fixes for scratched lenses all work by removing the coating, which does hide the scratch and does ruin the lens.

And never leave them on a car dashboard. Heat is a coating killer, and it can warp frames enough to change how they sit on your face - which is a fit problem people rarely trace back to where they left them.

What Nobody Tells You About Lens Coatings

Anti-fog coatings are the most fragile of all. They work by making the surface hydrophilic, and any oil, soap residue, or abrasion destroys the effect. If your anti-fog stopped working, cleaning is usually the reason.

Do not rub the inside of an anti-fog lens at all - rinse and air dry only. This one rule preserves anti-fog performance longer than anything else.

Hydrophobic coatings wear out on a schedule regardless. Typically one to two years with regular use. When water starts sheeting rather than beading, it has gone, and it can sometimes be reapplied with a spray-on treatment.

Salt water needs immediate rinsing. After sea swimming or coastal running, rinse the whole frame in fresh water the same day. Salt corrodes hinges and screws as well as sitting on the lens.

Sunscreen is quietly destructive. Some chemical UV filters attack plastic frames and coatings. Wash your hands after applying sunscreen before handling your glasses, and rinse the frame if it makes contact.

And the case matters more than the cleaning. A hard case prevents most damage, while a soft pouch with grit in it is an abrasive bag. Turn the pouch inside out and shake it occasionally - most people never have.

Mid-session, if you cannot rinse: blow the loose grit off first, then use a clean microfibre, or just leave the smear until you can rinse properly. A smeared lens for ten minutes is better than a scratched lens permanently.

Can a scratched lens be saved?

Coating scratches cannot be repaired. The layer is gone, and every polishing method removes more coating rather than restoring it.

Assess whether it matters first. Fine scratches at the edge of the lens have little practical effect on vision or on sun protection.

Scratches in the central vision area are different. They scatter light, which produces glare and eye strain - and that is the point at which the lens should be replaced.

Check whether replacement lenses are available. Many sport frames take interchangeable lenses, and replacing one lens is a fraction of the cost of the glasses.

A hazy lens still blocks UV. UV protection is built into the lens material, not the coating, so a scratched lens is not suddenly unsafe - it is just worse to look through.

And if you get headaches or eye strain after an hour in them, check for scratches, but also check the fit and the lens category. Persistent eye strain, changes in vision, or headaches that continue without the glasses are worth an optometrist appointment. This is general information, not medical advice.

FAQ: Cleaning Sport Sunglasses, Answered

What is the best thing to clean sunglasses with?

Lukewarm running water, one drop of plain washing-up liquid rubbed gently with fingertips, a thorough rinse, then air dry or pat with a clean microfibre cloth.

Can I use alcohol wipes or hand sanitiser?

No. Alcohol strips anti-reflective, hydrophobic, and anti-fog coatings. It is the fastest way to ruin a coated lens.

Why is dry-wiping so bad?

Salt, dust, and grit sitting on the lens become the abrasive. The cloth drags them across the surface and cuts fine scratches into coatings that are only nanometres thick.

How do I clean an anti-fog lens?

Rinse with water and air dry - do not rub the inside surface at all. Anti-fog coatings work by being hydrophilic and are destroyed by oil, soap residue, and abrasion.

How often should I wash my microfibre cloth?

Every few weeks with regular use. An old cloth carries embedded grit and becomes the thing causing the damage. Machine wash without fabric softener.

Can scratched lenses be polished out?

No. Every polishing method removes more coating. If the scratches are in the central vision area, replace the lens - many sport frames take interchangeable lenses cheaply.

What should I do if I have no water mid-workout?

Blow the loose grit off, then use a clean microfibre very gently - or simply live with the smear until you can rinse. A temporary smear beats a permanent scratch.

TL;DR:

• Dry-wiping causes nearly all lens damage. The salt and grit on the lens becomes the abrasive.
• The method: rinse under lukewarm water, one drop of washing-up liquid with fingertips, rinse thoroughly, air dry or pat with clean microfibre.
• Never: alcohol, hand sanitiser, ammonia, window cleaner, solvents, paper towel, or anything abrasive.
• Anti-fog coatings are the most fragile - rinse and air dry only, never rub the inside.
• Wash the microfibre cloth regularly, without fabric softener. An old cloth is the problem, not the solution.
• Rinse in fresh water the same day after sea or sweat, and keep sunscreen off the frames.
• Coating scratches cannot be polished out. Replace the lens if they are in the central vision area.

No water mid-session? Blow the grit off and live with the smear. Temporary beats permanent.