How to clean your glasses without scratching or ruining them

Glasses do not wear out on their own. They wear out little by little, in two-second gestures repeated ten times a day for three years.

This article is about cleaning them so that the lenses you collect today still look the same in two years’ time. None of it is optician’s fussiness: nearly every scratched lens we see across the counter has the same cause, and it is not a fall.

Why a lens gets scratched

The dust in the air is not fluff. Much of it is mineral particles, mostly silica: the same material as sand, and one of the hardest there is. Whatever hard coating or anti-reflective coating your lens carries is considerably softer than that.

Which gives the one rule that really matters:

Never rub a dry lens. Rubbing it dry means dragging an abrasive across the glass.

That is where the fine circular scratches in the middle of the lens come from after a few months. It is not a manufacturing fault and it is not a cheap lens: it is the jumper.

Two things worth knowing, and they are reassuring:

• A scratch does not change your prescription. The American Academy of Ophthalmology is explicit about it: light scratches do not alter the prescription or the protective features of the lens. They are annoying if they fall right on your line of sight, but they are not changing your eyesight.
• Extensive scratching, or loss of the coating, does cost you clarity and can reduce protection against ultraviolet light. At that point it is no longer cosmetic.

And one that is less reassuring: scratches cannot be polished out. On a prescription lens they cannot be removed. The surface is calculated to the micron and it is coated; sanding it would change the power and strip the layers. A scratched lens gets replaced. Which is why everything below is worth the trouble.

The method, step by step

Five steps. The first one is the one almost nobody does, and it prevents 90 % of the damage.

1. Rinse the glasses under the tap, in lukewarm water. Before you touch anything. This washes away the dust and the sand, which is what scratches. Lukewarm, not hot.
2. One drop of pH-neutral washing-up liquid. Rub it between your fingers until it lathers and apply it to the lenses with your fingertips. This is what the coating manufacturer itself recommends, so you can forget the myth that soap eats the anti-reflective coating. What you should avoid are creamy or glycerine soaps: they leave a film and make you rub more, which is exactly the opposite of the point.
3. Rinse thoroughly, again under running lukewarm water. Do not leave soap behind: it dries into marks.
4. Dry with a clean microfibre cloth, gently and without hurrying. Hold the frame on the side you are cleaning, not by the middle: if you hold it by the bridge and rub, you are bending the frame a little every time you clean it.
5. If you use a lens spray, spray the cloth, not the lens. Liquid landing on the lens ends up in the drill holes and the screws, and that is where rust starts and where a rimless frame works loose.

When there is no tap nearby — out in the street, in the car — lens spray on the cloth is the right substitute. What is never acceptable is breathing on them and rubbing.

What to use, and what never to use

These work:

• Running lukewarm water.
• One drop of pH-neutral washing-up liquid.
• Lens cleaning spray.
• A clean microfibre cloth.
• Single-use lens wipes, with a warning from the American Academy of Ophthalmology worth taking seriously: they can scratch if they are poor quality, if they are used badly, or if the lens has grit on it. On an unrinsed lens, a wipe scratches just as well as a jumper does.

About supermarket lens cleaning fluids. Some of them are perfectly good. The trouble is that there is no way of telling which: the label almost never states what is in the bottle. And the stakes are not evenly matched — the spray costs a few euros, while an anti-reflective coating that goes cloudy cannot be repaired: the whole lens is replaced. If you buy one elsewhere, check that it says explicitly that it is suitable for lenses with an anti-reflective coating and that it contains no alcohol or ammonia. And do not confuse it with the glass cleaner sitting on the shelf beside it, which usually does contain ammonia.

At the practice we sell the same fluid we use here in the workshop on our patients’ lenses: we know what is in it, which coatings it is compatible with, and what will not suit your frame. If you already have one at home and you are not sure about it, bring it in and we will take a look.

These do not, and they cause damage:

• Your T-shirt, your jumper, your shirt cuff. The fabric carries dust and the dust scratches. This is cause number one.
• Tissues, napkins, kitchen roll. Cellulose fibre: it scrapes, and it sheds lint on top.
• Household glass cleaner. Many contain ammonia, meant for bare glass, not for coatings on plastic.
• Bleach, vinegar, acetone or nail polish remover. Acetone attacks plastics and frame lacquers directly.
• The dishwasher. Strongly alkaline detergent, abrasive, and hot — all three at once. Neither the frame nor the coating is built for that.
• Saliva, or breathing on them and then rubbing. It neither cleans nor protects: it just lubricates the dust that was already there.

On alcohol: it is not needed. Soap and water do a better job, and there are frame lacquers and acetate frames that alcohol dries out or leaves matt. It is not our routine and we do not recommend it.

The cloth: the most neglected part

A microfibre cloth works because it traps grease. Which means it saturates: there comes a point when it picks nothing up and merely spreads what it is already carrying. A grey cloth that smears instead of cleaning is a cloth asking to be washed, not to be used again.

• Wash it often, by hand or in the machine, in warm water.
• No fabric softener. Softener leaves a film that cancels out the microfibre and then transfers to the lens.
• Keep it in the case, not loose in a bag or a pocket. A cloth that lives loose collects grit, and then the cloth becomes sandpaper.
• The little fabric pouch that came with the glasses is for storing them, not for cleaning them. Dirt gathers in the bottom of it.

Keep two or three and rotate them. They cost very little and they are the only thing that touches your lenses every single day.

Heat is what really kills a coating

Here is the damage that cannot be repaired and that almost nobody warns you about.

The coating manufacturer gives the figure: above 80 °C the lens and its coatings are damaged. The dashboard of a closed car in the sun, in Mazarrón in July, passes that temperature without the slightest difficulty.

What happens is that the lens and the layers on top of it expand at different rates. Because they are bonded to each other, that difference builds stress, and the coating ends up cracking into an extremely fine web — what the trade calls crazing. It looks as though the lens is broken. It is not: what has broken is the coating. And there is no fixing it; the lens gets replaced.

So:

• Never on the dashboard. Not even “just for a minute”.
• No saunas, no open ovens, no barbecues, no radiators. And not in direct sun on a table.
• Be careful with hairdryers and with the car’s hot air aimed at your face.
• Cold counts too. A frame can warp in hard cold: do not leave them in the car overnight in winter.

Here on the coast: salt, sun cream and sand

We live at the seaside, and that adds three enemies the manuals do not mention.

Salt. As it dries it crystallises, and those crystals are abrasive. Coming back from a walk along the seafront and wiping the lenses dry is the worst possible combination. Rinse with fresh water, always. And there is a second reason: salt corrodes screws, hinges and metal temples. A metal frame on the coast needs its screws tightened more often than one inland.

Sun cream. It is grease with solvents in it. It leaves a film that will not come off in one pass and makes you press harder with the cloth. Wash them with soap and water as soon as they get smeared; do not leave it until the evening.

Sand. Not one dry stroke. Rinse first, always, no exceptions. A single grain of sand between the cloth and the lens leaves a scratch that never goes away.

And the pool: chlorine is no friend of frame lacquers either. Rinse them when you get out.

How to take them off and where to put them

• Use both hands. Taking them off one-handed, pulling on one temple, twists the frame little by little. And this is not about looks: your prescription is calculated for a specific position of the lens in front of the eye. A twisted frame puts that lens in the wrong place, and with varifocals you feel it in the intermediate corridor.
• Do not wear them on your head. It splays the temples and gets hair oils on them.
• Never face down on a table. If you have no case to hand: folded, lenses facing up.
• A hard case beats a fabric pouch. A pouch protects from dust; it does not protect from a handbag.
• Avoid leaving them in the bathroom, where hairspray and aerosol deodorants land: they leave a film that is very stubborn to remove.

How often to bring them in

Two things we do here that extend the life of a pair of glasses more than any product will:

The ultrasonic bath. It is the gentlest and most effective way of lifting the dirt that builds up in the grooves, in the nose pads and around the rim of the lens, exactly where a cloth cannot reach. It takes a couple of minutes. Every six months is a sensible rhythm.

Adjusting the frame. As we said above, your prescription depends on where the lens sits. A frame that has slowly given way over the months drops the optical centre and has you looking through the wrong part of the lens. Five minutes puts it right.

You can drop into the shop and have both done without an appointment.

What people ask us most

Can scratches be polished out? No. Not with toothpaste, and not with the kits advertised online. At best they do nothing; at worst they strip off whatever coating is left.

Can I just have the anti-reflective coating redone and keep the lens? No. The coating is applied to the lens at the factory, in a vacuum. It is not a sticker you replace.

Is a scratch damaging my eyes? No. It is annoying and tiring, but it is not harming your eye or changing your prescription.

What about supermarket wipes? Ones made for glasses, yes, with the same precaution of rinsing first if there is grit. Baby wipes or surface disinfectant wipes, no: they contain oils or alcohols that have no business there.

Is any supermarket lens fluid good enough? Yours may well be, but the label will not tell you, and that is exactly the problem: if it contains alcohol or ammonia, the anti-reflective coating goes cloudy and there is no way back. Buy it where they can tell you what is in it. And if you already have one at home, bring it in and we will tell you whether you can carry on using it.

How often should I clean them? Once a day, properly, with water. That is far better than six dry passes.

They steam up with a mask, or when I walk into air conditioning. That is not dirt and rubbing will not fix it. There are anti-fog coatings and there are tricks to how they sit; ask us and we will look at it with your own glasses in front of us.