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extraocular muslces Flashcards

1
Q

what are horizontal eye movements

A
  • from left to right
  • adduction is movement from the eyes towards the nose
  • addduction is movement of the eye away from the midline

adduction and abbduction is movement around the vertical axis

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2
Q

what are vertical eye movements

A

moving the eye up is elevation

moving the eye down is depression

elevation and depression is movement around the horizontal axis

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3
Q

what are rotational/pivitol movements

A
  • intorsion- when the eye is turning in towards the nose
  • extorison - when the eye is turning outwards away from the nose

around and axis that goes from anterior to posterior

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4
Q

describe the different eye movements

A

if you face a patient with the eyes pointing straight ahead this = the primary position

if you cover right eye and observe the ducctions of the left eye - movement of the cornea away from the midline is abbduction , movement towards the midline is adduction

movement upwards is elevation
movemement downwards is depression

rotation of the upper cornea towards the midline is incylotorison or intorison

rotation away from from the midline is excylotorison or exorsion

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5
Q

what are the four rectus muscles

A

superior, inferior , medial , lateral

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6
Q

what are the oblique muscles

A

inferior oblique and superior oblique

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7
Q

what are the eom innervated by

A

superior rectus

medial rectus

inferior rectus

inferior oblique

(all innervated by cranial nerve 3)

superior oblique is innervated by the trochelear nerve ( cn 4)

lateral rectus is innervated by abducens nerve cn 6

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8
Q

describe the signifcance of the difference between the axis of the orbit and the eyeball

A

the axis of the eyeball is at 0 degrees

  • the orbit instead of being a pyramid face on is slightly off centre

it is 23 degrees from the orbit

  • resultant effect on the vertical axis

because the inferior and superior rectus is coming in at a oblique angle at 23 degrees - it means that they do more than just elevate or depress the eye

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9
Q

by how many degrees is the axis of the orbit and the axis of the eyeball offset

A

23 degrees - this has effect for pulling on muscles in the vertical axis

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10
Q

what are the cardinal positions of gaze

A

their is a difference between how we clinically test the extraocular muscles and what those extraocular muscles do to the eye in isolation

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11
Q

how do you test that the lateral rectus and medial rectus are working

A

medial rectus adducts the eye so you get them to test it by looking inwards

lateral rectus abbducts the eye so you get them to test it by looking outwards

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12
Q

how do you test that the superior oblique is working

A
  • you get them to look down and inwards
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13
Q

where do the 4 recti muscles originate from

A

four straight muscles

medial , lateral , superior , inferior

originate from common tendinous ring and move forward to insert into the sclera anterioly

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14
Q

what are the 4 recti muscles longest to shortest

A

longest -= supeior rectus , medial rectus , lateral rectus, inferior rectus

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15
Q

what are the contents of the superior orbital fissure that pass within the common tendinous ring

A
  • superior division of the oculomotor nerve
  • nasocillary nerve
  • inferior division of oculomotor nerve
  • abducens nerve
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16
Q

what is the common tendinous ring

A
  • oval thickening of the periosteum at the apex of the orbtial cavity
  • encloses the optic foramen and medial end of the superior orbital fissure
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17
Q

what is the spiral of tillaux

A

spiral connecting insertions of recti muscles

the 4 recti muscles do not insert at the same distance from the limbus

medial rectus inserts closest to the limbus, with the inferior , lateral and superior recti progresivley inserting farther away

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18
Q

which eom inserts closest to the limbus

A
  • the medial rectus at 5.5mm
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19
Q

which eom inserts furthest away from the limbus

A

superior rectus at 7.7mm

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20
Q

describe the medial rectus

A
  • largest extraocular muscle
  • origin - medial portion of the tendinous ring
  • travels anerioly and perices tenons capsule (fascile sheath ) close to the medial orbital wall, sends off medial check ligament

insertion - medial sclera - 5.5.mm from the limbus- most proximal to the limbus

innervation - inferior divison of the oculomotor nerve

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21
Q

describe the function of the medial rectus

A

function - rotates the eye medially - adduction

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22
Q

describe the lateral rectus

A
  • origin - lateral portion of the common tendinous ring

(small 2nd head with origin from the greater wing of the sphenoid)

  • travels anterioly close to the medial orbital wall , sends off the lateral check ligament

insertion - lateral sclera - 6.9mm from limbus

innervated by abducens nerve

23
Q

what is the function of the lateral rectus

A

rotates the eye laterally - abbduction

24
Q

by how many degrees is the axis of the orbit offset from the axis of the eyeball

A
  • the axis of the orbit is offset 23 degrees from the axis of the eyeball

this has signifcance for the movements of muscles which act in the vertical plane

25
Q

where do the rectus muscles origninate from

A
  • the rectus muscles originate from the annulus of zinn
26
Q

what is the function of the spiral of tillaux

A
  • the spiral of tillaux connects the insertions of the recti
27
Q

where does each rectus muscle insert in the limbus

A

medial rectus inserts closest to the limbus (5.5mm) with clockwise recti inserting further away until superior rectus (7.7mm)

28
Q

what is the medial rectus supplied by

A
  • the medial rectus is supplied by the inferior division of the oculomotor nerve and adducts the eye
29
Q

what is the lateral rectus supplied by and what is its function

A
  • supplied by abducens nerve and abducts the eye
30
Q

describe the superior rectus

A
  • orginates at the tendinous ring and attaches to the dural sheath of the optic nerve

passes forwards and laterally fascial sheath (tenons capsule) is connected to sheath of lps by a band of connective tissue

insertion - inserts 7.7mm posterior to the limbus - line of insertion is curved and oblique

innervated by the superior division of the oculomotor nerve
- nerve perices inferior surface then usually continues to supply levator

31
Q

describe the movements of the superior rectus

A
  • function - moves it up and in

elevates the eye

intorts the eye (rotates the eyeball medially on its anteroposterior axis

adducts the eye

(adduction - towards the nose

intorsion - bringing the top of the eye towards the nose

32
Q

describe the inferior rectus

A
  • origninates from the tendinous ring
  • passes forwards and laterally fascial sheath is attached to the sheath of io and to the suspensory ligament
  • insertion - 6.5mm form the limbus (second most proximal)

innervation - inferior division of the oculomotor nerve

33
Q

describe the function of the inferior rectus

A
  • fucntion - down and in

depresses the eye

extorts the eye (rotates the eyeball laterally on its anteroposterior axis)

adducts the eye

34
Q

how many oblique extraocular muscles are their

A

superior and inferior oblique

antagonists of each other

have an ‘’oblique course’’

dont originate from the ctr

35
Q

describe the superior oblique

A

origin - body of the sphenoid bone above and medial to the optic canal

belly runs forward between the roof and medial orbit giving rise to a rounded tendon

tendon then passes through a fibrocartilageous pulley - trochlea that is attached to the trochelea fossa of the frontal bone

then bends downward , backward and laterally slipping under sr

insertion - sclera posterior to the equator of the eyeball

innervation - trochlear nerve

36
Q

what is the function of the superior oblique

A

function - pulls the eye down and out

intorts the eye (rotates the cornea medially on its anteroposterior axis) depresses the eye in adduction

abducts the eye

if we ask the patient to look down and out to asess the function of the superior oblique the superior oblique could not be working but the lateral rectus and the inferior rectus could do the same thing

37
Q

describe the inferior oblique

A
  • the only muscle taking origin from the front of the orbit

origin - anterior orbtial floor - orbital surface of maxilla just lateral to the nasolacrimal canal

passes laterally , posteriolly and superiorly

it is inferior to the inferior rectus

fascial sheath is attached to that of the inferior rectus

insertion - into sclera under cover of lateral rectus

innervation - inferior division of the oculomotor nerve

38
Q

what is the function of the inferior oblique

A

function - up and out

extorts the eye (rotates the eyeball laterally on its anteroposterior axis)

elevates the eye in adduction

abducts the eye

39
Q

what is the oculocardiac reflex

A
  • decrease in pulse rate associated with traction applied to eom and/ or compression of the globe (when you tug on the eom during surgery can cause bradycardia)

the orbital contents is innervated by the opthalmic branch of the trigeminal nerve

  • the reflex is mediated by nerve connections between the opthalmic branch trigeminal nerve (v1) via the cillary ganglion and the vagus nerve of the parasympathetic nervous system

can cause cardiac arrest, tends to be more profound in neonates and children

40
Q

what is the difference between clinical testing and anatomical function

A
  • important to note that the gaze used for clinical testing is distinct from the anatomical function
    e. g. anatomical function of the superior oblique is too look down and out and we asess the patients superior oblique by getting the patient to abduct the eye and look down
41
Q

what is the function of the superior rectus and what is it innervated by

A

superior rectus intorts the eye and turns it up and in - innervated by the superior branch of the cn iii

42
Q

what is the inferior rectus innervated by and what is its function

A

inferior rectus extorts the eye and turns it down and in - innervated by the inferior branch of cn iii

43
Q

what does the superior oblique do and what is its function

A

superior oblique intorts the eye and turns it down and out - innervated by the trochlear nerve cn iv

44
Q

what does the inferior oblique do and what is it innervated by

A

inferior oblique extorts the eye and turns it up and out and it is innervated by inferior branch of cn III

45
Q

what is the oculocardiac reflex

A
  • bradycardia precipitated by pressure on orbital contents or the eom - nerves from the opthalmic branch of trigeminal nerve v1 communicate with the vagus nerve of the parasympathetic nervous system
46
Q

why do you have multiple actions of each of the eom

A

the axis of the orbit and the axis of the eyeball are offset

47
Q

what do oblique muscles do

A

abduct

48
Q

what is the difference between superior and inferior eoms

A

superiors intort wheras inferiors extort

49
Q

what is the difference between rectis and obliques

A
  • recti act according to their names and wheras obliques act opposite to their names
50
Q

where do all the recti muscles originate from

A
  • the common tendinous ring
51
Q

which muscle originates from the anterior wall of the orbit

A
  • the inferior oblique
52
Q

which muscle tendon attaches furthest away from the limbus

A
  • the superior rectus (7.7mm)
53
Q

what is the biggest extraocular muscle

A

the medial rectus

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