Pupillary response

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Dilation and constriction of the pupil

Pupillary response is a

size of the pupil, via the optic and oculomotor
cranial nerve.

A constriction response (

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 human adult exhibiting voluntary control over his iris muscles, where he can cause his pupil to dilate and constrict on command

A dilation response (

amphetamines; and some hallucinogenics (e.g. LSD).[2] 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.

Constricted (left) and dilated (right) pupil of the same eye

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,[3] uncertainty,[4] decision conflict,[5] errors,[6] physical activity[7] or increasing cognitive load[8] or demand. The responses correlate strongly with activity in the locus coeruleus neurotransmitter system.[9][10][11] The pupils contract immediately before REM sleep begins.[12] A pupillary response can be intentionally conditioned as a Pavlovian response to some stimuli.[13]

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.[14] 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.[15]

In ophthalmology, intensive studies of pupillary response are conducted via videopupillometry.[16]

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

Scheme showing sympathetic and parasympathetic innervation of the pupil and sites of lesion in a Horner's syndrome
Sympathetic connections of the ciliary and superior cervical ganglia
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

References

  1. PMID 7326222
    .
  2. PMID 1363080
  3. S2CID 12857616
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  4. PMID 22660479
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  5. S2CID 4960140
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  6. S2CID 220044505
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  7. PMID 36153491
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  8. S2CID 22762466
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  9. S2CID 535645
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  10. PMID 26711118
    .
  11. PMID 24510607
    .
  12. ^ 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.
  13. OCLC 6894644. {{cite journal}}: Cite journal requires |journal= (help
    )
  14. ISSN 0167-8760
    .
  15. OCLC 84657376. Archived from the original
    (PDF) on 2012-03-20.
  16. PMID 5439164
    .
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