In many parts of the world, nearly two out of three people wear corrective eyewear. And lately, many of us have the same complaint: Wearing a mask makes our glasses fog.

When we asked readers to send their questions about coronavirus, one of the most commonly asked questions was about how to solve the fogging problem. While the problem is new to us, it’s a daily challenge for health care workers. We asked them for suggestions on how to wear a mask while making sure we’re still able to see through our glasses.

Why does my mask make my glasses fog?

People who wear glasses already know that eyewear fogs when you walk out of a warm house into the cold outdoor air, or when you open an oven door. When we wear a mask, warm breath can escape through the top edges, along the tops of our cheeks. When the hot air lands on cooler lenses, it creates condensation on the surface and a foggy film. Cold weather makes the problem worse.

So how do I stop the fog?

You can start by improving the seal of the mask around the top of your face.

Mould your mask. Medical masks have built-in, bendable metal strips that you can mold to the bridge of your nose. You can add pipe cleaners to the top of a homemade fabric mask to get the same effect.

Tighten the mask. Adjust the ties or the ear loops so the mask fits snugly against your face.

“If the air is going out the top, you don’t have your mask on correctly,” said Shan Soe-Lin, a lecturer at the Yale Jackson Institute for Global Affairs. “Most of the breath should be going through the mask. If you feel the air going in or out around the mask, tighten the ties.”

Tape your mask. Another option is to use white athletic or medical tape or even an adhesive bandage to seal the top of the mask around the bridge of your nose.

“This is something a lot of medical students learn early on when they’re using eye protection goggles,” said Dr Andrew Janowski, instructor of pediatric infectious diseases at Washington University School of Medicine St Louis Children’s Hospital.

Don’t use non-porous household tapes like packing tape or duct tape, which could irritate skin. Taping is a lot of work for a short trip outside, but might be warranted if you’re caring for a sick person.

Pull up your mask. An easier tip for day-to-day mask wear is to use the weight of your glasses to block the air. Pull the mask up over the bridge of the nose as high as you can (make sure it’s still under your chin too) and let your glasses rest on top of the mask. I tried this and it works pretty well for me, but it depends on the shape and style of your eyewear.

Do home lens treatments work?

If you can’t stop the fogging by tightening the seal of your mask, you can try anti-fog home remedies to coat your lenses.

Try soapy water. A British surgeon published a paper in 2011 showing that washing your glasses with soapy water and letting them air dry can help.

Soap acts as a surfactant — which stands for surface active agent — and the soapy water leaves behind a thin film that stops the water molecules from forming droplets that lead to fog.

“As a person who wears glasses I found myself affected by this issue when operating,” said Dr Sheraz Malik, senior clinical fellow at Manchester University Hospitals NHS Foundation Trust and the author of the report.

He noted that operating rooms tend to be kept at low temperatures, making the “misting” problem a real issue for surgeons who wear spectacles.

“I haven’t timed it, but the technique reliably works for more than a half-hour when operating,” Dr Malik said. “Obviously if the face mask is tightly secured on the nose, there is less escape of the moisture towards the glasses and the technique works for longer.”

Try other home remedies. Popular suggestions for treating lenses this way include baby shampoo, toothpaste and shaving cream. (Vinegar is often suggested, but most experts say it doesn’t work.) The main challenge of treating your lenses is adding enough of the substance to stop the fog, but not so much that the coating itself blurs the lens.

Skip the swimmer’s remedy. Swimmers and scuba divers have a regular trick to keep glasses from fogging. They spit into their goggles or masks and rub it around. But given that we’re dealing with a respiratory virus and trying to stop the spread of germs, spitting on your glasses is not advised during a pandemic.

I’ve tried everything, and nothing works. What’s wrong?

Now the bad news. Menzies notes that many eyeglasses are now treated with special protective coatings that resist glare and smudges. The problem is that the coatings also may resist anti-fog treatments, including home remedies like soapy water and commercial treatments like FogTech.

Marjorie Lamb, a 71-year-old writer in Toronto, stepped out on her chilly balcony last week to test the various anti-fog methods on her glasses. She treated one lens and not the other to find the most effective treatment.

She tried vinegar and varying combinations of hand and dish soaps, but nothing worked.

Then she remembered her glasses had been treated with a special coating called Crizal, which promises protection against UV rays, glare, scratches, smudges, dust and water.

The coating, unfortunately, also appeared to protect the lenses from Lamb’s anti-fogging efforts. “I was wondering if the coating made a difference,” she said.

If nothing works, do I just have to live with foggy lenses when I wear a mask?

As a last resort, you can try pushing your glasses forward on your nose to allow more air to circulate and stop the fog. The downside is that it could distort your vision.

“This seemed to work best of all,” Lamb said.

“The only caveat is that it threw off my perception slightly. It might be less disruptive with a lesser prescription.” Fogging also will be less of a problem as summer approaches and outdoor temperatures get closer to the temperature of your breath.