People need to see the prices on items or the money in their wallet to pay for a ticket - but they are blinded as the air from the top of the mask condenses as moisture on the lens.

One technique is to stop the air from your mouth escaping through the top of the mask straight to the lenses.

"Sadly, there is no magic trick, such as putting the mask or glasses on first that will stop fogging. Improving the fit around the curve of the nose and cheeks is the best approach," according to two academics at the University of Adelaide, Craig Lockwood and Zoe Jordan.

Surgeons have already been there. They have to wear masks when they wield the scalpel (where getting it wrong by a millimetre is a matter of life and death).

"Get a roll of micropore tape - $2 at any chemist. Tape the mask along the bridge of your nose and cheeks. Then glasses on top. Another way is to put a folded tissue across the bridge of your nose," according to Dr Julie Miller, who says she can't operate with foggy lenses.

Use the tissue if tape is irritating, she advises.

Canberra GP Dr Antonio Di Dio also advises: "Tape the top of mask to your face so steam doesn't rise."

There is an elegance issue with this solution, according to Dr Di Dio. He thinks it can make you look like a "dork" or a "serial killer".

A variant on the "seal the top of the mask" solution is to use a twist tie like the ones you get to seal bags of bread, or even a pipe cleaner. You can mould either at the top of the mask to give a tight fit across the bridge of the nose.

Many ready-to-wear masks have built-in nose bridges.

The Victoria health department says a stocking as an extra layer of a mask can also help: "If you want to improve the fit of your mask you can add a nylon stocking over the mask and tie at the back of the head."

The other idea is to treat the glass on the lens so that it is resistant to the moisture from your breath. Soap helps.

According to the journal of the Royal College of Surgeons: "Immediately before wearing a face mask, wash the spectacles with soapy water and shake off the excess. Then, let the spectacles air dry or gently dry off the lenses with a soft tissue before putting them back on. Now the spectacle lenses should not mist up when the face mask is worn."

The University of Adelaide's Craig Lockwood and Zoe Jordan advise: "Wash your glasses with soap and water (such as regular washing up liquid), then dry them with a microfibre cloth. This type of cloth typically comes free with each pair of glasses.

"You can also buy cheap microfibre cloths from most optometrists. Facial tissues may leave lint, which attracts moisture to the lenses. Soap reduces surface tension, preventing fog from sticking to the lenses."

They say shaving foam also does the trick.

"Apply a thin layer of shaving cream to the inside of your glasses, then gently wipe it off. The residual shaving cream will protect the lenses from misting up."

And there are de-misting sprays on the market: "You can use a commercial de-misting spray that dries clear. But make sure this is compatible with your lens type or existing coatings on your lens. You can buy demisting spray online or from your optometrist."

It's worth experimenting. How much your glasses mist up depends on temperature.

If you are outside and it's cold, they are more likely to get foggy as the warm air on your body condenses on the cold lens.

Try tucking the mask over the outside of the lens.

Specsavers says: "The reason why your glasses keep fogging up is because your breath is escaping out the top of your mask. If you can seal the top of the mask with the weight of your specs, you may find it much easier."

The company also suggests contact lenses as one alternative.

But do wear a mask. It's the law.

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