Foggy glasses when wearing a mask

I have an appointment with my ophthalmologist today. Last time I was there, I had to read the eye chart with my glasses and mask on. My glasses fogged up, so this task was difficult to achieve.

I just learned to use a tissue inside your mask, at the top, to prevent fogging. I'm going to try it and see how things go.

Years ago, I had anti-fogging spray that I used on my lenses. Perhaps I should get something similar again.