What is prefix of pupil?

There isn't a specific prefix for "pupil" in the sense of a student.

However, "pupil" can also refer to the black center of the eye. In this context, the prefix "pupill-" is sometimes used.

Here are some examples:

* Pupillometry: the measurement of pupil size

* Pupillographic: pertaining to the recording of pupil movements

So, while "pupil" as a student doesn't have a specific prefix, it does when referring to the part of the eye.