Eyeglass lenses are not heat resistant

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It comes as a surprise for most customers when I tell them that the coating of plastic lenses does not tolerate high temperatures. These warnings should be taken seriously as heat-resistance of coating is only around 140-180 F.

The steam that comes from an oven when opening it can already ruin the coating of the lenses. The lenses suffer the most from fast change in temperature.

You shouldn’t leave your eyeglasses to direct sunlight either, for example, on the dashboard of your car. You also shouldn’t go to sauna with your glasses on. If you cannot manage there without glasses, take at least your oldest pair of glasses, as the coating will be damaged in the high temperature.

When you are cleaning your eyeglasses, remember that hot water can also damage the surface of the lenses. Therefore, use lukewarm water.

The best heat-resistance in plastic lenses is 230 F and it can be obtained with Hoyan Eyas –material. The heat resistance of glass lenses is notably higher than that of plastic lenses.

How do you notice thermal damage?

If there is thermal damage in your lenses, you may find that the glasses seem stained all the time and you might even think that your vision has worsened. You can check your lenses by holding them against light. If there is thermal damage, you can see patterns in the lens resembling a spider web.

There is no way to fix this kind of damage, so the only option is to buy new lenses.

Please note that the advice and tips given in this blog are based on Finnish regulations and laws. Therefore, you need to verify the regulations and laws in your country from your own optician, optometrist or eye specialist.

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  1. Matti says

    The blog is now bi-lingual? 🙂

  2. Hi Matti!
    This was just a small test period. In the future I’ll focus to write new content only in Finnish.