Visual system- eye movements Flashcards

1
Q

what is duction?

A

eye movement in one eye

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2
Q

what is version?

A

simultaneous movement of both eyes in same direction

right= dextroversion

left= levoversion

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3
Q

what is vergence?

A
  1. simultaneous movement of both eyes in opposite direction
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4
Q

what is convergence?

A
  1. simultaneous adduction (inward) movement in both eyes when viewing a near target
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5
Q

what is a saccade?

A

short fast burst of eye movement

can be voluntary or involuntary

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6
Q

what are the types of saccade?

A
  1. reflexive saccade to external stimuli (acquiring new external target)
  2. scanning saccade (reading book)
  3. predictive saccade to track objects
  4. memory-guided saccade (in absence of external stimuli)
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7
Q

what is a slow pursuit?

A

sustained slow eye movement - up to 60deg/sec

driven by motion of moving target across the retina

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8
Q

what are the extraocular muscles?

A
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9
Q

Where do the extraocular muscles originate?

A

5/6 from back of orbit

inferior oblique comes nasally

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10
Q

where does the superior rectus attach and what do they do?

A

attached to eye at 12 o clock

elevates the eye maximally, moves eye up

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11
Q

where does the inferior rectus attach and what does it do?

A

attached to eye at 6 o clock

depressses eye maximally (moves eye down)

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12
Q

what does the lateral rectus do and where does it attach?

A

also called external rectus, attaches on temporal side of eye, moves eye towards outside of head (towards temple)

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13
Q

what does the medial rectus do and where does it attach?

A

also called internal rectus, attaches on nasal side of eye, moves the eye towards the middle of the head (towards the nose)

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14
Q

where is the superior oblique attach and what does it do?

A

attached high on temporal side of eye

passes under superior rectus

moves eye in a diagonal pattern down and out

travels through trochlea

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15
Q

what does the inferior oblique do and where is it attached?

A

(faded muscle)- attached low on nasal side of eye and passes over inferior rectus. Moves eye in diagonal pattern (up and out)

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16
Q

what is the innervation of extraocular muscles?

17
Q

which muscle in involved in looking in each direction?

18
Q

how is extraocular muscle testing done?

A

Isolate muscle to be tested by maximizing its action and minimizing the action of other muscles

19
Q

what muscle is used for each movement of eye?

A
  • Abduction – Lateral Rectus
  • Adduction – Medial Rectus
  • Elevated and Abducted – Superior Rectus
  • Depressed and Abducted – Inferior Rectus
  • Elevated and Adducted – Inferior Oblique
  • Depressed and Adducted – Superior Oblique
20
Q

what is a 3rd nerve palsy?

A
  • Only muscles not innervated by 3rd cranial nerve are working
21
Q

what are the signs of a 3rd nerve palsy?

A
  • Affected eye down and out
  • Droopy eyelid (ptosis) (loss elevator palprebrae superioris- upper lid lavatory muscle innervated by superior branch of oculomotor nerve (3rd))
  • Unopposed superior oblique innervated by 4th nerve (down)
  • Unopposed lateral rectus action innervated by 6th nerve (out)
22
Q

what happens in a 6th nerve palsy?

A
  • Affected eye unable to abduct and deviates inwards
  • Double vision worsen on gazing to the side of affected eye
23
Q

what are the causes of 3rd, 4th and 6th nerve palsy?

24
Q

what is nystagmus?

A

oscillatory eye movement

25
Q

what is optokinestic nystagmus?

A

smooth pursuit + fast phase reset saccade

  • Eyes track along grating motion, with smooth pursuit up to a limit and resets eye position to centre with a burst of fast saccade motion
  • Results in cycles of slow phase smooth pursuit, alternating with fast phase reset saccade in opposite direction
26
Q

what is an optokinetic nystagmus reflex useful for?

A

testing visual acuity in pre-verbal children

by observing the presence of nystagmus movement in response to moving grating patterns of various spatial frequencies

signifies subject has sufficient visual acuity to perceive the grating pattern