Pupillometer, also spelled pupilometer, is a medical device intended to measure by reflected light the size of the pupil of the eye. In addition to measuring pupil size, current automated pupillometers may also be able to characterize pupillary light reflex. Some instruments for measuring pupillary distance (PD) are often, but incorrectly, referred to as pupilometers.

Pupillary distance (PD), more correctly known as interpupillary distance (IPD) is the distance in millimeters between the centers of each pupil.