Pupil Evaluation Walter Huang, OD Yuanpei University

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Pupil Evaluation

• Walter Huang, OD
• Yuanpei University
• Department of Optometry

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Pupil

• A black circular opening in the center of the
  iris
• It is surrounded by the pupillary margin of the
  iris

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Pupil

• Purpose
• To control the amount of light entering the eye

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Normal Pupils

• They are round in shape and relatively equal in
  size
• Their size vary from 1 to 8mm in diameter
• Normal pupils range from 3 to 5mm in ambient
  light conditions
• Miotic pupils are less than 3mm
• Mydriatic pupils are greater than 7mm

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Pupil Size

• Determined by
• Age
• Level of retinal illumination
• Emotional factors (i.e., pain, pleasure, fear)
• Amount of accommodation and/or convergence (near
  reflex)

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Pupil Contraction and Dilation

• Controlled by two muscles of the iris
• Sphincter muscle (pupil constriction)
• Innervated by the parasympathetic nervous system
• Dilator muscle (pupil dilation)
• Innervated by the sympathetic nervous system

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Muscles of the Iris and Pupil
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Sphincter Muscle

• The pupil size is mainly determined by the
  contraction or relaxation of the sphincter muscle
• The sphincter muscle responds to signals coming
  from the short ciliary nerve and constricts the
  pupil
• It is innervated by parasympathetic fibers

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Dilator Muscle

• The pupil size is secondarily determined by the
  contraction or relaxation of the dilator muscle
• The dilator muscle responds to signals coming
  from the long ciliary nerve and dilates the pupil
• It is innervated by sympathetic fibers

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Nerve Pathway

• Afferent pathway
• Afferent nerve or input nerve
• Nerve that carries sensory information towards
  the central nervous system (i.e., brain and
  spinal cord)
• Sensory pathway for pupil constriction

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Nerve Pathway

• Efferent pathway
• Efferent nerve or output nerve
• Nerve that carries impulses away from the central
  nervous system (i.e., brain and spinal cord)
• Parasympathetic and sympathetic pathways for
  pupil constriction and dilation

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Afferent Pathway of the Pupil Light Reflex

• Sensory pathway for pupil constriction
• Axons from retinal ganglion cells (input)
• ?
• Optic nerve ? Optic chiasm ? Optic tract
• 
  ?
• Edinger-Westphal ? Pretectal nucleus
• nucleus

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The Pathway of the Pupillary Reaction to Light
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Efferent Pathway of the Pupil Light Reflex

• Parasympathetic pathway for pupil constriction
• EW nucleus (output) ? Cranial nerve III
  
• Accommodation fibers ? ? ?
• Ciliary body Ciliary
  ganglion
• ? ?
  ?
• Iris sphincter muscle ? Short ciliary nerve

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Direct and Consensual Response

• The signal is passed to both sides of the
  midbrain so that light information given to one
  eye is passed on to both pupils equally

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Direct Response

• Direct light reflex
• The constriction of the ipsilateral pupil to the
  light stimulus

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Consensual Response

• Consensual light reflex
• The constriction of the contralateral pupil to
  the light stimulus

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Total Blindness

• Total blindness due to bilateral cortical lesion
  does not affect the light reflex

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Total Blindness

• Total blindness in one eye due to retinal or
  optic nerve problem
• Shine light in normal eye have direct response
  but no consensual response (similar to shine
  light in bad eye)
• Shine light in blind eye no direct response but
  have consensual response (similar to shine light
  in good eye)

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Efferent Pathway of the Pupil Light Reflex

• Sympathetic pathway for pupil dilation
  Hypothalamus ? Spinal cord
• 
  ?
• Superior cervical
  ganglion
• ?
• Cranial nerve V ? Eyelid muscles
• ?
• Long ciliary nerve ? Dilator muscle

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Anatomy of Sympathetic Pathway
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Near Reflex

• Accommodation, convergence, and pupil
  constriction (miosis) occur at the same time
• Artificially induced convergence causes
  accommodation and miosis
• Artificially induced accommodation causes
  convergence and miosis

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Near Reflex

• Miosis is the weakest of the three responses so
  that it cannot induce accommodation and
  convergence
• Some accommodation fibers innervate the pupil
• The convergence pathway is located close to the
  Edinger-Westphal nucleus so that there may be
  some crossing over with accommodation and miosis

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Pupil Testing

• Purpose
• To examine the afferent and efferent neurological
  pathways responsible for pupillary function

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Pupil Testing

• Recent onset of the following may be life- or
  sight-threatening
• Asymmetry in pupil size
• Abnormal response to light or accommodation

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Pupil Testing

• Procedure consists of four steps
• Observation (screen for anisocoria)
• Direct and consensual response
• Swinging flashlight test
• Near reflex test

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Pupil Testing

• The first three steps should be performed on
  every patient
• The last step should be done when a relative
  afferent pupillary defect (RAPD) is found in the
  third step

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Observation

• In bright and dim illumination
• Look for asymmetries in pupil size
• Measure pupil size (to the nearest 0.5mm)

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Direct Response

• In dim illumination
• Instruct the patient to look at the distant
  target
• Shine the light into the patients right eye
• Observe the size and the speed of the pupil
  constriction of the patients right eye
• This is the direct response or direct light
  reflex of the right eye

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Consensual Response

• In dim illumination
• Instruct the patient to look at the distant
  target
• Shine the light into the patients right eye
• Observe the size and the speed of the pupil
  constriction of the patients left eye
• This is the consensual response or consensual
  light reflex of the left eye

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Swinging Flashlight Test

• Also known as the Marcus Gunn test because it is
  a test for pupillary escape or the Marcus Gunn
  response

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Swinging Flashlight Test

• In dim illumination
• Move the light between the eyes rapidly, leaving
  it on each eye for 3 to 5 seconds
• Observe the direction of response (constriction
  or dilation) and the size of each pupil at the
  moment that the light first arrives there and
  during the 3 to 5 second observation period

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Marcus Gunn Response

• Also known as a relative afferent pupillary
  defect (RAPD)

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Marcus Gunn Response

• When the afferent pathway (retinal ganglion cells
  to optic chiasm) of one eye is damaged, a light
  stimulus to the affected eye will not be able to
  induce a pupillary light reflex
• As a result, both pupils will be larger when
  light is directed into the affected eye

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Marcus Gunn Response

• When the afferent pathway (retinal ganglion cells
  to optic chiasm) of one eye is damaged, a light
  stimulus to the normal eye will still be able to
  induce a normal direct and consensual response
• As a result, both pupils will be smaller when
  light is directed into the non-affected eye

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Marcus Gunn Response

• Loss of vision due to corneal, lenticular,
  vitreous, refractive, or emotional causes will
  not produce the Marcus Gunn response

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Near Reflex Test

• Instruct the patient to look at the distant
  target
• The examiner holds up a target containing fine
  detail approximately 25cm from the patient
• Ask the patient to fixate the near target and
  look for pupil constriction
• Note the speed of the constriction and the
  roundness of each pupil

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Recording

• If all the pupil responses are normal
• Record PERRLA, -MG
• Pupils Equal Round and Responsive to Light and
  Accommodation
• Negative Marcus Gunn response

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Recording

• Describe any pupil abnormalities
• Inequality of size (anisocoria)
• Direct (D) and consensual (C) responses based on
  speed and amount of constriction on a scale of 0
  to 4

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Expected Findings

• PERRLA, -RAPD
• Direct response is approximately equal to
  consensual response
• Pupil reaches 90 of maximum size in 5 seconds
• Problem with the sympathetic pathway causes
  dilation lag so that anisocoria is greater at 5
  seconds than at 12 seconds

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Light-Near Dissociation

• In normal patients, the amplitude of the pupil
  response to light is equal to the amplitude of
  the pupil response to near
• Light-near dissociation (i.e., near response is
  greater than light response) is rare
• It may be associated with afferent defects (blind
  eye), midbrain defects (Argyll Robertson pupil),
  and efferent defects (third nerve defect)

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Argyll Robertson Pupil

• Damage to the parasympathetic pathway
• Possible causes neurosyphilis (lesion around the
  Edinger-Westphal nucleus), long-term diabetes, or
  alcoholism
• Presumed neurosyphilis until proven otherwise

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Argyll Robertson Pupil

• Both pupils are small and respond poorly or not
  at all to light (no direct and consensual
  response)
• Swift response to near (light-near dissociation)

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Argyll Robertson Pupil
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Argyll Robertson Pupil
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Adies Tonic Pupil

• Damage to ciliary ganglion or postganglionic
  fibers of the short ciliary nerve
  (parasympathetic pathway problem)
• Usually unilateral, common in females
• The affected eye is dilated and reacts poorly to
  light (poor direct and consensual response)

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Adies Tonic Pupil

• Near reaction is strong, slow, and tonic
• When the patient refixates at distance, the pupil
  redilates very slowly

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Adies Tonic Pupil
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Adies Tonic Pupil
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Horners Syndrome

• Pupillodilator dysfunction
• Damage to the sympathetic pathway
• Common cause lung cancer
• Signs ptosis (droopy eyelid), miosis, facial
  anhydrosis (sweat gland denervation), iris
  heterochromia (congenital Horners)
• Pupil reacts normally to light and near

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Horners Syndrome
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Horners Syndrome
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Summary

• Anisocoria in light parasympathetic problem
• Cranial nerve III defect, intracranial pressure,
  drug-induced mydriasis, Adies pupil, iris
  damage, simple anisocoria
• Anisocoria in dark sympathetic problem
• Horners syndrome, simple anisocoria

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References

• Neuro-Ophthalmology (Section 5) - American
  Academy of Ophthalmology. Chapter 4, Pupil.
• Primary Care Optometry, pp. 145-147.
• The Massachusetts Eye and Ear Infirmary
  Illustrated Manual of Ophthalmology, pp. 198-205.