Pupillary Light Reflex Simulator

Neuro-ophthalmology · Afferent & efferent pupillary pathways · Examiner's view (patient facing you)

EXPLORE
Controls
Light stimulus
Circuits / layers
Sympathetic (dilator) pathway
Lesion mode
Tip: click a structure directly on the diagram to place or remove a lesion — or use the buttons below.
Afferent (sensory limb)
Central (midbrain)
Efferent (motor limb)
Legend
Afferent (light)
Efferent (parasymp.)
Near reflex
Symp. 1° (central)
Symp. 2° (pregangl.)
Symp. 3° (postgangl.)
Sweating (anhidrosis = struck)
Active signal
Lesion
Findings
Right pupil
—
resting
Left pupil
—
resting
Normal pupils
Shine a light into either eye, or use the swinging flashlight. Add a lesion to see how the direct and consensual responses change.
📋 Instructor Notes
🔬 Simulator set to answer

Reading the pupils
Direct = the lit eye constricts. Consensual = the other eye constricts too (bilateral pretectal → Edinger–Westphal projection). The swinging flashlight test exposes a relative afferent defect: the affected pupil paradoxically dilates when the light reaches it.
References & sources

Anatomy and clinical correlations are drawn from the peer-reviewed and standard neuro-ophthalmology sources below. This simulator is an educational model and is not a substitute for clinical examination or judgement.

  1. Belliveau AP, Somani AN, Dossani RH. Pupillary Light Reflex. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2023 Jul 25. Available from: ncbi.nlm.nih.gov/books/NBK537180
  2. Akova U, Yoo H, Launico MV. Neuroanatomy, Pupillary Light Reflexes and Pathway. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2025 Sep 15. Available from: ncbi.nlm.nih.gov/books/NBK553169
  3. Broadway DC. How to test for a relative afferent pupillary defect (RAPD). Community Eye Health. 2012;25(79&80):58–59. Available from: PMC3588138
  4. McDougal DH, Gamlin PD. Autonomic control of the eye. Compr Physiol. 2015;5(1):439–473. doi:10.1002/cphy.c140014.
  5. Szabadi E. Functional organization of the sympathetic pathways controlling the pupil: light-inhibited and light-stimulated pathways. Front Neurol. 2018;9:1069. doi:10.3389/fneur.2018.01069.
  6. Relative Afferent Pupillary Defect. EyeWiki (American Academy of Ophthalmology). Available from: eyewiki.org/Relative_Afferent_Pupillary_Defect
  7. Roediger HL III, Butler AC. The critical role of retrieval practice in long-term retention. Trends Cogn Sci. 2011;15(1):20–27. doi:10.1016/j.tics.2010.09.003 [Basis for the retrieval-first quiz: answer before the simulator reveals the lesion.]
Founded by Dr. Adeolu Morawo  ·  Playground Neurology