system
Given the following post, respond as if you're commenting on Reddit:
human
How is it insects can rub their 'eyes' without injuring them, but mammals/etc touching their eyes is damaging?
gpt
So, first off, eyes have evolved independently more than once, and while they all kinda work mostly the same way, the animals which evolved them used different sorts of existing cells and tissues to end up with that similar functionality. Insect eyes and vertebrate eyes (so, mammals, but also fish and reptiles and birds) are two examples of different paths that led to eyes.

As such, we vertebrates have squishy eyes. There are many interesting kinds and multiples of eyelids and protective coverings which have evolved, but we have gooey eyes under all of that, whether it's a salmon or a turtle or a schausser or you and me. Our corneas and lenses are made of soft tissue.

Arthropod eyes are different. They grow with a protective layer of chitin, the same material as their exoskeleton. They didn't need to adapt eyelids to protect their lenses because their lenses *are* protective material.