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Extraocular muscles Flashcards

1
Q

What are the 6 Extraocular muscles in the eye

A

Superior recuts
Inferior recuts
Lateral recuts
Medial rectus

Superior oblique
Inferior oblique

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2
Q

What is three types of duction

A

Horizontal movement (along vertical axis)
- adduction, eye turns nasally
- abduction, eye turns temporally

Vertical movement (along transverse axis)
- elevation (supraduction)
- depression (infraduction)

tortinal movment (along sagittal axis)
- Intorsion (incycloduction), eyes rotate nasally
- Extorsion (excycloduction), eye rotates temporally

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3
Q

What is the primary posistion of gaze

A

Look straight, ahead position

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4
Q

What is the secondary posistion of gaze

A

Looking up, down, left or right

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5
Q

What is the tertiary posistion of gaze

A

Oblique position of gaze

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6
Q

what is the longest rectus muscle

A

SR, followed by MR, LR then IR

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7
Q

Where do the 4 recti start from

A

Annules of Zinn

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8
Q

Spiral of tillaux

A

MR attach closes to limbus, followed by IR, LR, SR (clockwise)

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9
Q

How is the superior rectus inserted into the sclera

A

passes laterally forward and pierces the sclera, 7.55mm posterior to limbus

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10
Q

What is the angle of visual axis for the Superior Rectus

A

Line of insertion is slightly curved and oblique, makes a angle of 23 degres with visual axis when eye in primary position

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11
Q

What is the primary action of superior rectus

A

Elevation
- at its maximum when eye is abducted 23 from primary position so that the visual line is parallel to the muslce pull

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12
Q

What is the seconday and tertiary action of superior rectus

A

Secondary action:
Intorsion

Teritary action:
Adduction
- 67 degrees from primary position so visual line is right angle to muslce pull

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13
Q

What is the nerve supply of superior rectus

A

Oculomotor (CN III) nerve

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14
Q

What is the blood supply of superior rectus

A

Muscular branch of opthalmic artery

Drained from superior opthalmic vein

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15
Q

How is the inferior rectus inserted into the sclera

A

passes laterally forward and pierces the sclera, 6.55mm posterior to limbus

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16
Q

What is the angleof visual axis for inferior rectus

A

23 degress with visual axis when eye in primary position

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17
Q

What is the primary action of the inferior rectus

A

Depression
- at its max. when eye abducted 23 degress from primary position so that visual line is parallel to muscle pull

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18
Q

What is the secondary and tetiary action of the inferior rectus

A

Secondary adction:
Extorsion

Tertiary action:
Adduction
- eye adducted 67 degress from primary position

How to rmb:
When ur Inferior= you depressed and extorsion, added tgt gives you 23 degress of depression

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19
Q

what is the nerve supply of inferior rectus

A

Oculomotr nerve

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20
Q

What is the blood supply of Inferior rectus

A

Ateries:
- Inferior muscular branch of opthalmic artery

  • Infra- orbital artery

Venous drainge:
- inferior opthalmic vein

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21
Q

How does the medial part peirce the scelra

A

Start from medial part of annulus, attached to dural sheath of optic nerve n medial wall of the orbit to form medial check ligment

Passes forward close to medial wall n pierces sclera area, inserts around 5.5mm from limbus

LARGEST EOM

22
Q

What is the action of the medial rectus

23
Q

What is the nerve supply of the medial rectus

A

Occulomotor (CN III) nerve

24
Q

What is the blood supply of medial rectus

A

Supplied by inferior muscular branch of opthlamic artery

25
How does the lateral rectus pierce the sclera
Spreads across the superior orbital fissure from the annulus, passes forward close to lateral wall of orbit, lie below lacrimal gland Inserts about 7mm from limbus
26
What is the action of the lateral rectus
Abduction
27
Which nerve is the lateral rectus innervated by
Abducent Nerve (CN VI)
28
What is the blood supply of the lateral rectus
Superior muscular branch and lacrimal branch of opthalmic artery Drainage is inferior opthalmic vein
29
How is the superior oblique inserted into the sclera
Inserted into periorbita at apex of orbit (medial n superior to annulus of zinn) Runs nasally to trochlea fossa before tuning back to insert under the SR at upper lateral posterior quadrant of the globe Longest and thinnest muscle
30
What is the angle with the visual axis made by superior oblique muscle
Line of action of msucle make angle of 51 degres with sagital line when eye in primary position
31
What is the primary action of the Superior Oblique muscle
Intorsion - at its maximum when eye is abducted 39 degress from the primary position forming right angle to the musle pull
32
What is the secondary and teritary action of the Superior Oblique
Secondary action: Depression - Max when eye is adducted by 51 degree from primary position so that visual line is parallell to muscle pull Tertiary action: Abduction - at its max when eye is abucted by 39 degress from primary position forming right angle to muscle pull
33
What is the nerve supply of the Superior Oblique
Trochlear nerve (CN IV)
34
What is the blood suuply of the superior oblique
Muscular branch of the opthalmic artery drainage from superior opthalmic vein
35
How does the inferior oblique pierce the sclera
Only voluntary muscle within orbit that comes from front of orbit Begins attachment at lateral edge of lacrimal fossa at anterior nasal margin of orbit and turns back between IR and the orbital floor to insert into sclera SHORTEST EOM
36
What is the angle with the visual axis made by inferior oblique muscle
Line of action of muscle makes an angle of 51 degress wth sagittal line when eyes in primary position
37
What is the primary action of the inferior oblique muscle
Extorsion - at its max when eye abducted 39 degress from primary position forming right angle to muscle pull
38
What is the secondary and teritary action of inferior oblique muscle
Secondary action Elevation - at its max when eye is adduced by 51 degress from primary positon so that visual line is parallel to muscle pull Tertiary action Abduction - at its maximum whn eye is abducted 39 degress from primary position forming right angle to muscle pull
39
What is the nerve supply of the inferior oblique muscle
Inferior divions of oculmotor nerve( CN III)
40
What is the blood supply of the inferior oblique muscle
Inferior muscular branch of opthalmic artery and branch of infra-orbital artery Venous drainage from inferior ophthalmic vein
41
what are the types of binocular eye movement
Version vergence saccades smooth pursuits Optokinetic nystagmus Fixation eye movement
42
What is version
Movement of two eyes in the same direction: Dextroversion - looking right Laevoversion - looking left Supraversion - looking up Infraversion - looking down
43
What is Yoke muscle (contralateral synergists)
A pair of muscles one in each eye which contract stimultaneously during version movement
44
what is hering's law of equal innervation
Under this law, there is equal amount of innervation to the muscle in each eye that move the 2 eyes in the same direction (version)
45
What is vergence
Movement of 2 eyes in the opp. direction to maitain single binocular vision -convergence (nasally) - divergence (temporally)
46
What is saccades
Shift of gaze from one fixation point to another, usually voluntary intiated Ends with slight reverse saccade (due to overshot of gaze), where lok boeyond the subject and come back to it Fixation eye movement
47
What is smooth pursuit movement
Voluntary eye movement to maintain foveal fixation on moving targets Eyes move at same speed as target so taht image reminas stationary on retina Target motion is needed to elicit smooth pursuit
48
What is Optokinetic Nystagmus
A series of resolvable object move across the visual field, they will each be tracked for a short distance and then the fixation will be transferred to the next object A type of induced nystagmus easily elicited in all person with a normal visual mechanism
49
Give 2 scernations showing Optokinetic Nystagmus ( OKN)
When the body is in motion and the subject is gazing at the environment - train nystagmus, when sitting in MRT and looking out the window When the subject is still and the environment moves around them (rotating durm with stripes)
50
How is OKN seen clinically
Use of rotating drum with striples on it - starts iwht smooth pursuit folloowing a stripe until it passes out of visual field - then a saccadic eye movment in the opposite direction trying to get a clear image on the fovea This results in a jerk nystagmus
51
What is fixation
Fixation mechanism works to maintain the object on the fovea Small trembelling movements stil occur even when eye is in the steadiest position - vibration from EOM
52
What are the three types of fixational eye movement
Drift Microsaccades Tremors

Ocular anatomy (15 decks)

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