Over continued use, the anti-fog coating of your glasses may become worn out.
This is a standard behavior of anti-fog coating and not a product defect.

You can order new anti-fog glasses and replace them yourself.

To order new anti-fog glasses, please click on "New support ticket"

Please have a look at the following video outlining on how to change the glasses of your frame yourself.

Make sure to use the supplied lint free cloth to do this.