What are those glasses things people wear on their eyes?

So here is my story, I apologise to anyone if I sound ignorant here but I haven't been exposed to a multi cultural society so I am unaware of many things. I am from a smallish town/village in Australia, where isn't many multiculturalism. It's got a fair amount of people. But anyway, I always had a plan to explore and travel the world. I've been to Melbourne and Sydney few times growing up. As I'm 17 years old currently, I decided to travel to some European cities with some of my local villagers, to cities like Paris London and Rome. To my shock, I saw so many people have this plastic thing around their head, with two transparent glass covering their eyes. It was like sunglasses, which I am familiar with, but it had see-through lenses. I mean, I had never ever really seen people wearing those. In London and Rome, I remember every 1 in 2 or 3 people had those things on their eyes. I had never ever seen people wear those here over in my local town or know any famous celebrities with those things on. I mean, I remember 1 or 2 Middle eastern immigrants used to wear those but back then I used to think they were a cultural/religious thing like covering hair is for Muslim women. I asked one of the people I was with, why people were wearing those things so often and he suggested it treats eye infections. I seriously have hard time believing so many people have eye infections in Europe. So my question is, what are those things people wear? How come I've never seen those here?

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