The Vale Tudo matches I fought had a different rules.
Sometimes it was simply no biting and others simply obey the ref and respect the stoppage.
I fought in few that throats and eyes were valid and I could tell who went for them.
It rarely worked.
As any fighter knows, hitting the HEAD clean isn't always easy, less so for the jaw, EVEN LESS so for the throat or eyes.
I had one guy try to "tiger claw" my throat !
He got elbowed up the yin-yang and got a dislocated elbow for his troubles.
I have a scratch over my eye from an attempted eye gouge and another on my cheek ( very faint), they got ****ed up royally for those attempts.
People learn very quickly that cheap shots don't work as well as they think and only make things worse for them.

That said, I know a few ways to make eye gouges and throat strikes/grabs work very, very well.