What does prefixes kera means?

There is no prefix "kera" in the English language. It's possible you're thinking of a word that contains "kera" as part of its root or is a misspelling of a real prefix.

Could you provide more context or the word you're thinking of? For example, are you thinking of a scientific term, a medical term, or something else?

With more information, I can help you understand the meaning of the word or prefix you're looking for.