Can prozac, hydtoxyzine or prednisolone cause one pupil to be bigger than the other?

A rare side effect of Prozac is mydriasis (dilated pupil) and one pupil may be affected than the other (anisocoria) and I assume it could happen in your case.

Many people have pupils which are larger on one side (anisocoria), and this is a normal variant. If Prozac did result in pupillary size increase, the asymmetry would be bilaterally exaggerated. But unlikely that a drug would produce a new pupillary change otherwise. If this is troublesome, discuss appropriate steps with your doctor.