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NBB1 > Eye Movements > Flashcards

Eye Movements Flashcards

1
Q

Where is vision optimized?

A

Fovea

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2
Q

What nervous system (symp or parasymp) is working with high light?

A

High light, pupil constricts –> pupillary sphincter muscle –> contraction

parasympathetic

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3
Q

What nervous system (symp or parasymp) is working with dim light?

A

Pupillary dilator muscle –> contrction

(sympathetic)

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4
Q

What does cilliary muscle have intrinsic muscle control over?

A

controls lens shape (enables the lens to focus when objects are closer to the eye)

Cilliary muscles Contract to allow release of the lens –> accomodation

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5
Q

Extraocular muscles and actions

A
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6
Q

Define:

esotropia

A

eye in (medial gaze)

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7
Q

Define:

exotropia

Bonus: What lesion would produce exotropia?

A

eye out (lateral gaze of eye)

Caused by lesion affecting medial rectus

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8
Q

Define:

Hypertropia and hypotropia

A

eye up and eye down respectively

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9
Q

What muscles move the eye vertically when the eye is ADDucted?

A

oblique muscles

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10
Q

What muscles move the eye vertically when the eye is ABducted?

A

Superior and inferior rectus muscles

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11
Q

What is the general location of motor nuclei of eye in midbrain and pons?

A

dorsal medial

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12
Q

What are the GSE of eye movements?

(Bonus: where are the nuclei located?)

A

General Somatic Efferents: lower motor neurons to 4 extra ocular muscles and levator palpebrae superioris

  • Oculomotor nucleus (midbrain)
  • Trochlean nucleus (midbrain)
  • Abducens nucleus (pons)
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13
Q

What is the GVE of eye movements?

A

Edinger-Westphal nucleus (general visceral efferent)

  • Preganglionic parasympathetic to pupillary constrictor and ciliary muscle of lens
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14
Q

What does CN III Innervate?

A

4 extraocular muscles and 1 eyelid muscle (GSE)

  • That is the medial rectus, inferior rectus m. superior rectus m., inferior oblique, and superior levator m.
  • All except lateral rectus and superior oblique
  • See red paths (only) in image
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15
Q

What are the extraocular actions of CN III?

A
  • move eye up and down
  • Move eye towards the nose
  • Rotate it externally (with upward component)
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16
Q

What lesion/syndrome would you suspect with ptosis?

A
  • CN III lesion or
  • Horners syndrome
  • Myasthenia gravis
17
Q

What causes a blown pupil?

Bonus: what’s the medical term for it?

A

GVE (Edinger-Westphal nucleus) lesion –> mydriaosis

  • E-W (Parasymp) innervates ciliar and constrictor muscles.
  • Lesions cause mydriaosis (dialated pupil) and loss of accomodation
18
Q

What is miosis and what causes it?

A

Miosis = constricted pupil (with Horner’s syndrome), cuased by lesion in sympathetic innervation to dilator muscle.

19
Q

What is the path of light reflex (considering constriction response)?

A

Light to eye –> Afferent limb: CN2 –> some info crosses, some doesn’t –> Wrap around midbrain –> enter pretectal nucleus (synapse)–> send info bilaterally to E-W nucleus –> sends info bilatterally to pupillary constrictor muscles of eyes (Efferent limb: CN3)

20
Q

Signs/sx of left optic nerve lesion = afferent pupillary defect

(Swinging flashlight test)

A

Pupil constricts to light in normal eye, but when light is moved quickly to the defective eye, it will seem to dilate in respose (bc the input is “less”)

21
Q

Signs/sx of lesion of CN III

A
  • No direct response but yes to indirect/consensual response to light
  • Pure: ptosis (eye down and out); pupil blown
  • Partial: (no direct or consensual response in affected, both direct and consensual response in unaffected)
    • Shine light in affected eye:
      • no response to light in the affected eye
      • do get constriction in consensual eye
    • Shine light in unaffected eye:
      • direct response in affected eye
      • no consensual response in unaffected
22
Q

How to distinguish betwn horners and E-W or CN III lesion in a pt with ptosis?

A

Look to the pupils

23
Q

What damage is suspected with the following sx?

  • Mydriasis - on left eye
  • Loss of pupillary constriction -right eye
  • Loss of accomodation -right lens will not change curve to adjust to view near objects
A

CN III damage E-W on “right”:

  • Mydriasis - pupil on affected side dilated (“blown” pupil)
  • Loss of pupillary constriction - ipsilateral eye
  • Loss of accomodation - ipsilateral lens will not change curve to adjust to view near objects
24
Q

What do you suspect is affected?

  • Mydriasis - pupil on affected side dilated (“blown” pupil)
  • Loss of pupillary constriction - ipsilateral eye
  • Loss of accomodation - ipsilateral lens will not change curve to adjust to view near objects

plus

  • Exotropia - ispilateral eye “down and out” when pt looks straight ahead
  • Inability to move the ipsilateral eye vertically or medially
  • Diplopia
  • Ptosis - ipsilateral eyelid droops
A

CN III damage to E-W with GSE components to extra-ocular muscles and eyelids

25
Q

What do you suspect?

clinical triad of “blown” pupil, hemiplegia, and coma

A

Uncal herniation: transtentorial herniation

  1. Oculomotor nerve: ipsilateral (usually) CN III signs
  2. Cerebral peduncles: hemiplegia (contralateral)
  3. Reticular formation: decreased consciousness or coma
26
Q

What is the innervation/action of the trochlear nerve (CN IV)?

A

GSE to Superior Oblique Muscle

  • Primary Action: intorsion
    • Also depresses (in adducted positon) and abducts
27
Q

What is the clinical presentation of lesion of a right trochlear nerve?

A

CN IV palsy: extorsion with hypertropia (often seen with head tilt to prevent double vision)

NB: could also be a left trochlear nucleus lesion, though rare

28
Q

What lesion would be responsible for paralysis of the lateral rectus, seen with esotropia?

What could be some causes?

A

Pathway: abducent nucleus in caudal pons to CN VI - GSE to the lateral rectus muscle

Causes: increased intracranial pressure bc the brainstem is pushed downwards and CN VI is stretched

29
Q
A
30
Q
A

NBB1 (10 decks)

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