Pupil Pro: A Learning Tool for Teaching About Pupil Light Response

At a Glance

Pupil Pro is an interactive teaching tool that models neuronal circuits that control the constriction and dilation of the eye’s pupils. Pupil reaction to light is an important diagnostic tool for various ocular issues and also used to help detect brainstem damage. Students can find the complex neuronal pathways difficult to visualize and the impact of specific damage to parts of the pathway challenging to remember. Pupil Pro is an educational tool to help students explore and learn the role and function of specific components in the neuronal network that controls pupil size and the effect that specific damage has on the ability of both pupils to respond to light.


Both light and the nervous system influence pupil size and physicians will often test the light sensitive components of the neuronal circuit by shining a light in either eye. In a healthy individual, both pupils will constrict if light is shone in either eye. Specific lesions in the neural pathways may result in one or both pupils not constricting properly. The pathways involved in controlling pupil size are complex and learning the components of each neuronal circuit, as well as the impact of how lesions in different locations will affect the pupillary response is often challenging for students. Novel teaching devices, especially interactive devices, can help more clearly demonstrate these complexities to students.


The Pupil Pro device comprises two model eyes mounted on a platform and a series of LED lights run across the platform surface simulating neuronal pathways controlling pupil size. These model pathways include specific neurons and their synapses. When light is shone in either model eye, a light sensor detects the light and sequential LED lights show the flow of information through labeled neurons and synapses. This is followed by mechanical closure of apertures representing the pupils of each eye. A control area allows the input of different states representing isolated or broad neuronal damage to the relevant pathways as well as allowing changes to the parasympathetic or sympathetic drive into the circuits. Damage is indicated by illumination of red LED lights within a specific area, and the appropriate effect of the damage on one or both pupils results when light is shown in either model eye (Figure 1). The speed and strength of the response can also be adjusted to adapt for and challenge students at different levels of skill or to allow narration while the “neuronal signal” travels through the circuits. Once an input is chosen, a light can be shown in one or both eyes and watch the LED response in the neurons and then the pupil constriction in the eye model. From there they can see the effect of the input and learn to diagnose if the input was not known. This interactive tool makes it easier for students to see the flow of information in the system and visualize the results.

Figure shown of the Pupil Pro in use

Figure 1. Red LED lights indicate damage to a pathway, controlled by the system inputs at the switch board.


  • Portable and easy to use
  • Novel tool for teaching complex neuronal circuits and the results of injury to those circuits
  • Interactive and hands-on demonstration of neuronal pathways and the effects of injury
  • Adaptable speed and strength of response for students at different levels
  • Utilization for learning and experimentation as well as testing and student evaluation


  • Student education, including general medical, ophthalmology, and neuroscience
  • Physician demonstration/education to patients
Last Updated: January 2024
Reference Number