Pupillary Response

  • Introduction
  • Video& Results
  • Materials
  • Procedure
  • Preparation & Notes
  • Download Files

Pupillary Response - Light reflex


The eye responds to changes in light by altering the diameter of the pupil. When ambient light is low, the pupil is large (top, right). When intense light interacts with the retina at the back of the eye, the pupil shrinks (bottom, right). Muscles of the iris, in which the pupil is a simple hole, cause these changes. The pupillary constrictor muscle shrinks the pupils in bright light, while the radial dilator muscle widens it in dim light. Both eyes should respond in the same manner, even when light is shone only in one eye. When the pupillary response is observed in the eye where light has been shone directly, it is called the ipsilateral response. When the light is shone in one eye, and the response is observed in the other, this is called the contralateral response.



Video Demonstrations

Pupillary Response by Paul Kingston


Materials – Pupillary Response

  • pen light
  • video camera with computer connectivity
  • computer with internet connection (for sharing video files)
  • chair for still seating


  1. Have student sit in chair in front of the video camera and begin filming on the right eye.
  2. While filming, shine a pen light on the left eye (contralateral response). Next, shine pen light at the right eye (ipsilateral response).
  3. The film can be shown in real time on a monitor, emailed to the student etc.