Eye Movements

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Eye Movements

• Donna L. Hill, MD
• Neuro-ophthalmology
• Departments of Neurology and Ophthalmology
• UFShands Jacksonville

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Normal Eye Movements

• Objective Foveation
• Extraocular muscles
• Muscle innervation CNs III, IV, and VI
• Cranial nerve nuclei
• Three primary types of movements
• Pathologic eye movements

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Objective foveation

• fovea most sensitive portion of retina
• we need to orient, either voluntarily or
  reflexively, to important stimuli
• accomplished by directing our eyes to a target so
  that it is projected onto the fovea
• to maintain foveation, we depend on visual
  feedback as the primary source of information on
  eye movement accuracy

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Extraocular muscles

• Superior rectus moves eye up
• Inferior rectus moves eye down
• Medial rectus moves eye in (a-d-duction)
• Lateral rectus moves eye out (a-b-duction)
• Inferior oblique moves eye up when it is in an
  adducted position also extorts the eye.
• Superior oblique moves eye down when it is
  adducted also intorts the eye.

left
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Isolating Extraocular Muscles
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CN III
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CN III

• Superior division
• - Superior rectus muscle
• - Levator palpebrae superioris muscle
• Inferior division
• - Medial rectus muscle
• - Inferior rectus muscle
• - Inferior oblique muscle
• - Parasympathetic innervation to pupil

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CN IV CN VI
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CN VI
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Coordination of Eye Movements

• Separate systems exist to control each different
  subtype of eye movement saccades, smooth
  pursuit, and vergence
• May be nuclear or supranuclear control
• May be reflexive or voluntary
• Separate systems exist to govern vertical and
  horizontal eye movements

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Targeting Eye Movements

• Saccades Quick, darting conjugate movements
  which direct the eyes to a new target.
• Smooth pursuit A slower conjugate movement
  which allows for tracking of a moving object, or
  of a stationary object while we are moving.
• Convergence A dysconjugate movement of both
  eyes toward the midline to allow for focusing on
  a near object by adjusting the angle between the
  eyes.

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Variety of pathways contribute to saccadic
control and smooth pursuit
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Saccades

• Under the control of three different areas in the
  brain
• voluntary saccades - frontal eye fields
  (Brodmanns area 8)
• reflexive saccades to complex stimuli - parietal
  lobes (Brodmanns area 7)
• reflexive saccades to elementary stimuli -
  superior colliculi

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Voluntary Saccades (horizontal)
results in saccade to contralateral space
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Voluntary Horizontal Saccades
FEF
FEF
CEREBRAL HEMISPHERE
III
MIDBRAIN
III
PONS
VI
VI
PPRF
PPRF
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Yoking Mechanism
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Reflexive Saccades
- to complex stimuli originates in area 7 of the
parietal lobe - to elementary stimuli originates
in superior colliculi dorsolateral prefrontal
cortex involved in planning of eye mvts
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Smooth Pursuit

• Two types
• Voluntary (actually termed smooth pursuit)
  movements - originate in the temporo-parietal
  lobe
• Reflexive - which are under vestibular nuclear
  control alone and constitute what is called the
  vestibulo-ocular reflex (VOR).

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Voluntary Smooth Pursuit

• originates near the angular gyrus - Area 39 at
  the temporal parietal occipital junction
• cells in this region are able to compute the
  speed and direction of a moving object
• results in ipsilateral smooth pursuit

IPSI
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Optokinetic Reflex

• Combination of saccades and smooth pursuit that
  allow tracking of targets in turn (e.g. counting
  sheep as they jump over a fence).
• smoothly pursue one target, then saccade in the
  opposite direction to pick up the next target
• parieto-temporal junction (smooth pursuit area)
  projects down to ipsilateral vestibular nucleus,
  inhibits it allowing ipsilateral smooth pursuit
• then, the FEF of the same hemisphere generates a
  saccade back (contralateral) to the next target

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Reflexive Smooth Pursuit - VOR

• maintains gaze on a target despite head movement
• reflex arc semicircular canal opposite the
  head turn detects motion and activates the ipsi
  vestibular n. which deactivates its inhibitory
  input on the ipsilateral VI
• results in eyes turning opposite to the head turn

p339 Medical Neuroscience, Nadeau et al
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Convergence

• When areas of the occipital cortex detect a
  discrepancy in the retinal projection from each
  eye and amount of blur, a signal is sent to
  initiate convergence.
• To bring a near object into focus actually
  involves convergence, accomodation (lens
  curvature increases) and pupillary constriction.
  Together, these 3 movements are called the near
  triad.

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Pathologic eye movements

• Muscle
• Trauma, entrapment, inflammation, infiltrating
  diseases
• Neuromuscular Junction
• myasthenia gravis, botulism, organophosphate
  poisoning
• Cranial nuclei or nerve
• Brainstem stroke, hemorrhage, multiple
  sclerosis, tumor, trauma
• Subarachnoid space Increased intracranial
  pressure, aneurysm, meningitis, sarcoidosis,
  autoimmune
• Cavernous sinus Tumor, sinus thrombosis,
  pituitary apoplexy, sphenoid sinusitis,
  carotid-cavernous fistula, Tolosa-Hunt syndrome
• Orbit Trauma, tumor, infection

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right cranial nerve III palsy
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right cranial nerve VI palsy
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(No Transcript)
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Gaze Palsy

• inability to look in a particular direction (ie.
  neither eye can look right)
• lesion in the FEF, the PPRF, or the CN VI nucleus
  
• Lesion in the FEF unable to look
  contralaterally, eyes deviate toward the lesion,
  can be overcome with VOR
• Lesion in PPRF or CN VI nucleus inability to
  look ipsilaterally with either eye

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Voluntary Horizontal Saccades
FEF
FEF
CEREBRAL HEMISPHERE
III
MIDBRAIN
III
PONS
VI
VI
PPRF
PPRF
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Left MLF lesion intranuclear ophthalmoplegia
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Yoking Mechanism
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Acknowlegdements

• Dr. Tariq Bhatti and his patients for clinical
  images
• Dr. Angela McSwain, Dr. Nadeaus text, Peter Duus
  ( Topical Diagnosis in Neurology), and Frank H.
  Netter (Ciba Collection of Medical Illustrations,
  Vol 1)
• Dr. Nancy Newman and Dr. Valerie Biousse,
  Neuro-ophthalmology Emory University