Pupillary response

Pupillary response is a physiological response that varies the size of the pupil between 1.5 mm and 8 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. A dilation response (mydriasis), is the widening of the pupil and may be caused by adrenaline; anticholinergic agents; stimulant drugs such as MDMA, cocaine, and amphetamines; and some hallucinogenics (e.g. LSD). Dilation of the pupil occurs when the smooth cells of the radial muscle, controlled by the sympathetic nervous system (SNS), contract, and also when the cells of the iris sphincter muscle relax. The responses can have a variety of causes, from an involuntary reflex reaction to exposure or inexposure to light—in low light conditions a dilated pupil lets more light into the eye—or it may indicate interest in the subject of attention or arousal, sexual stimulation, uncertainty, information content, decision conflict, errors, physical activity or increasing cognitive load or cognitive demand. These relationships are investigated in the context of task-invoked pupillary response. The responses correlate strongly with activity in the locus coeruleus neurotransmitter system. The pupils contract immediately before REM sleep begins. A pupillary response can be intentionally conditioned as a Pavlovian response to some stimuli. Some humans have the ability to exert direct and voluntary control over their iris sphincter muscles and dilator muscles, granting them the ability to dilate and constrict their pupils on command, regardless of lighting condition and/or eye accommodation state. However, this ability is very rare, and its potential use or advantages are unclear. The latency of pupillary response (the time in which it takes to occur) increases with age. In ophthalmology, intensive studies of pupillary response are conducted via videopupillometry. Anisocoria is the condition of one pupil being more dilated than the other.

Physiological response that varies the size of the pupil

Pupillary response is a physiological response that varies the size of the pupil between 1.5 mm and 8 mm,^[1] via the optic and oculomotor cranial nerve.

A constriction response (miosis),^[2] 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.

A dilation response (mydriasis), is the widening of the pupil and may be caused by adrenaline; anticholinergic agents; stimulant drugs such as MDMA, cocaine, and amphetamines; and some hallucinogenics (e.g. LSD).^[3] Dilation of the pupil occurs when the smooth cells of the radial muscle, controlled by the sympathetic nervous system (SNS), contract, and also when the cells of the iris sphincter muscle relax.

The responses can have a variety of causes, from an involuntary reflex reaction to exposure or inexposure to light—in low light conditions a dilated pupil lets more light into the eye—or it may indicate interest in the subject of attention or arousal, sexual stimulation,^[4] uncertainty,^[5][6][7] information content,^[6][7] decision conflict,^[8] errors,^[9] physical activity^[10] or increasing cognitive load^[11] or cognitive demand. These relationships are investigated in the context of task-invoked pupillary response. The responses correlate strongly with activity in the locus coeruleus neurotransmitter system.^[12][13][14] The pupils contract immediately before REM sleep begins.^[15] A pupillary response can be intentionally conditioned as a Pavlovian response to some stimuli.^[16]

Some humans have the ability to exert direct and voluntary control over their iris sphincter muscles and dilator muscles, granting them the ability to dilate and constrict their pupils on command, regardless of lighting condition and/or eye accommodation state.^[17] However, this ability is very rare, and its potential use or advantages are unclear.

The latency of pupillary response (the time in which it takes to occur) increases with age.^[18]

In ophthalmology, intensive studies of pupillary response are conducted via videopupillometry.^[19]

Anisocoria is the condition of one pupil being more dilated than the other.

Pupillary responses

	Constriction (Parasympathetic)	Dilation (Sympathetic)
Muscular mechanism	Relaxation of iris dilator muscle, activation of iris sphincter muscle	Activation of iris dilator muscle, relaxation of iris sphincter muscle
Cause in pupillary light reflex	Increased light	Decreased light
Other physiological causes	Accommodation reflex	Fight-or-flight response, sexual arousal
Corresponding non-physiological state	Miosis	Mydriasis

See also

[edit]

• Cycloplegia
• Dilated fundus examination
• Iris sphincter muscle
• Pupillary light reflex
• Pupillary reflex
• Pupillometry
• Pupilometer
• Task-invoked pupillary response

References

[edit]

1. ^ McDougal, David H.; Gamlin, Paul D. (2015). "Autonomic Control of the Eye". Comprehensive Physiology. 5: 439–473. doi:10.1002/cphy.c140014. PMC 4919817.
2. ^ Ellis CJ (November 1981). "The pupillary light reflex in normal subjects". The British Journal of Ophthalmology. 65 (11): 754–9. doi:10.1136/bjo.65.11.754. PMC 1039657. PMID 7326222.
3. ^ Jaanus SD (1992), "Ocular side effects of selected systemic drugs", Optom Clin, 2 (4): 73–96, PMID 1363080
4. ^ Hess EH, Polt JM (August 1960). "Pupil size as related to interest value of visual stimuli". Science. 132 (3423): 349–50. Bibcode:1960Sci...132..349H. doi:10.1126/science.132.3423.349. PMID 14401489. S2CID 12857616.
5. ^ Nassar MR, Rumsey KM, Wilson RC, Parikh K, Heasly B, Gold JI (June 2012). "Rational regulation of learning dynamics by pupil-linked arousal systems". Nature Neuroscience. 15 (7): 1040–6. doi:10.1038/nn.3130. PMC 3386464. PMID 22660479.
6. ^ ^{a b} Basgol, Hamit; Dayan, Peter; Franz, Volker H. (2025-02-01). "Violation of auditory regularities is reflected in pupil dynamics". Cortex. 183: 66–86. doi:10.1016/j.cortex.2024.10.023. ISSN 0010-9452.
7. ^ ^{a b} Basgol, Hamit. "Modality-general sensitivity of pupil responses to regularity violations". osf.io. doi:10.31234/osf.io/um9fe_v1. Retrieved 2025-10-21.
8. ^ Lin H, Saunders B, Hutcherson CA, Inzlicht M (May 2018). "Midfrontal theta and pupil dilation parametrically track subjective conflict (but also surprise) during intertemporal choice". NeuroImage. 172: 838–852. doi:10.1016/j.neuroimage.2017.10.055. PMID 29107773. S2CID 4960140.
9. ^ Decker, Alexandra; Finn, Amy; Duncan, Katherine (2020-11-01). "Errors lead to transient impairments in memory formation". Cognition. 204 104338. doi:10.1016/j.cognition.2020.104338. ISSN 0010-0277. PMID 32593745. S2CID 220044505.
10. ^ Kuwamizu, Ryuta; Yamazaki, Yudai; Aoike, Naoki; Ochi, Genta; Suwabe, Kazuya; Soya, Hideaki (2022-09-24). "Pupil-linked arousal with very light exercise: pattern of pupil dilation during graded exercise". The Journal of Physiological Sciences. 72 (1): 23. doi:10.1186/s12576-022-00849-x. ISSN 1880-6562. PMC 10717467. PMID 36153491.
11. ^ Kahneman D, Beatty J (December 1966). "Pupil diameter and load on memory". Science. 154 (3756): 1583–5. Bibcode:1966Sci...154.1583K. doi:10.1126/science.154.3756.1583. PMID 5924930. S2CID 22762466.
12. ^ Aston-Jones G, Cohen JD (2005-07-21). "An integrative theory of locus coeruleus-norepinephrine function: adaptive gain and optimal performance". Annual Review of Neuroscience. 28 (1): 403–50. doi:10.1146/annurev.neuro.28.061604.135709. PMID 16022602. S2CID 535645.
13. ^ Joshi S, Li Y, Kalwani RM, Gold JI (January 2016). "Relationships between Pupil Diameter and Neuronal Activity in the Locus Coeruleus, Colliculi, and Cingulate Cortex". Neuron. 89 (1): 221–34. doi:10.1016/j.neuron.2015.11.028. PMC 4707070. PMID 26711118.
14. ^ Murphy PR, O'Connell RG, O'Sullivan M, Robertson IH, Balsters JH (August 2014). "Pupil diameter covaries with BOLD activity in human locus coeruleus". Human Brain Mapping. 35 (8): 4140–54. doi:10.1002/hbm.22466. PMC 6869043. PMID 24510607.
15. ^ Lowenstein O, Feinberg R, Loewenfeld IE (April 1963). "Pupillary Movements During Acute and Chronic Fatigue: A New Test for the Objective Evaluation of Tiredness" (PDF). Investigative Ophthalmology. 2 (2). St. Louis: C.V. Mosby Company: 138–157. Archived from the original (PDF) on 2012-03-19.
16. ^ Baker LE (1938). "The Pupillary Response Conditioned to Subliminal Auditory Stimuli". Ohio State University. OCLC 6894644. {{cite journal}}: Cite journal requires |journal= (help)
17. ^ Eberhardt, Lisa V.; Grön, Georg; Ulrich, Martin; Huckauf, Anke; Strauch, Christoph (2021-10-01). "Direct voluntary control of pupil constriction and dilation: Exploratory evidence from pupillometry, optometry, skin conductance, perception, and functional MRI". International Journal of Psychophysiology. 168: 33–42. doi:10.1016/j.ijpsycho.2021.08.001. ISSN 0167-8760.
18. ^ Feinberg R, Podolak E (September 1965). Latency of pupillary reflex to light stimulation and its relationship to aging (PDF). Federal Aviation Agency, Office of Aviation Medicine, Georgetown Clinical Research Institute. p. 12. OCLC 84657376. Archived from the original (PDF) on 2012-03-20.
19. ^ Ishikawa S, Naito M, Inaba K (1970). "A new videopupillography". Ophthalmologica. 160 (4): 248–59. doi:10.1159/000305996. PMID 5439164.