Pupillary response is a physiological response that varies the size of the pupil between 1.5Â mm and 8Â mm, via the optic and oculomotor cranial nerve.
A constriction response (miosis), is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/opioids or anti-hypertension medications. Constriction of the pupil occurs when the circular muscle, controlled by the parasympathetic nervous system (PSNS), contracts, and also to an extent when the radial muscle relaxes.