Dear Eyeglass World,
I love my new eyeglasses. They look great on, and my vision has never been better. Except on some occasions when I wear my glasses outside and then come into my warm home or office, they get fogged up. It also happens when I’m cooking, and I reach in the oven to pull out whatever’s cooking. Why does this happen, and is there something I can do to make it stop?
Bryce in New York
Your question is really more about science than it is optometric care! Remember how you learned in school about water and the three states it takes: solid, liquid and gas? What’s happening to your glasses is really just an evidence of moisture in the air (and on your skin) and how it changes form based on the temperature.
If you’ve been out in the cold, you’ve probably “seen” your breath when you blow out a warm breath of air. What you see as your “breath” is actually a cloud of moisture. When your glasses fog up walking into a heated room, it’s the same idea. Moisture on your glasses heats up, condensing into a layer of fog over your lenses – foggy glasses!
When you reach your head into the oven, it’s the same concept! The moisture on your lenses gets heated quickly when you’re exposed to the blast of hot air from the oven. The invisible water vapor molecules turn into a thin layer of water molecules on your lenses. The opposite effect can also happen. If you’re in a nice and toasty room, and then walk into a freezer, the moisture in the air will change states and give you foggy glasses immediately!
Sometimes your glasses will fog up just from sweat coming off of your body. Anyone who wears their glasses to the gym already know this. The heat and perspiration generated from your face can become a glasses fog. Make sure you can always see the treadmill in front of you!
How do you stop the glasses fog? There’s no real way to stop the fogging up from happening, but you can use an anti-fog spray on your lenses. This is essentially a water repellent that keeps moisture away from your lenses and protects them from condensation. Ask your Eyeglass World optometrist if she can recommend a certain brand of anti-fog spray.
Otherwise, just keep a soft cloth on hand for when your glasses go through a quick temperature change. Remember, the drier your lenses, the less fog you’ll see!