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MD4001 Week 3 > 6. Orbit, muscles around the eye > Flashcards

6. Orbit, muscles around the eye Flashcards

1
Q

What bones make up the orbit?

A

Roof: Orbital plate of the frontal bone
Medial wall: Orbital plate of ethmoid
Lateral wall: Body of sphenoid, lesser wing of sphenoid, optic canal, superior orbital feature, greater wing of sphenoid
Floor: Orbital plate of maxilla and lesser orbital fissure

The lateral rim formed from the zygomatic bone
Superior rim: From frontal bone

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2
Q

What is the axes of the orbit?

A

Medial walls almost parallel
Lateral wall at about 90 degrees
Leads to bases directed anterolaterally, and apices directly posteromedially

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3
Q

What are the vessels present at the apex of the orbit?

A

In optic canal is the ophthalmic artery, central retinal artery and vein.

In superior orbital fissure is:

  • Inferior ophthalmic vein
  • Superior ophthalmic vein
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4
Q

What are the nerves present at the apex of the orbit?

A

In superior orbital fissure above tendinous ring:

  • Lacrimal nerve CN V1 branch
  • Frontal nerve CN V1 branch
  • CN IV

In superior orbital fissure within tendinous ring:

  • Superior branch of CN III
  • Nasociliary nerve V1
  • Inferior branch of CN III
  • CN VI

In optic canal is CN II

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5
Q

What connective tissue supports the eyeball?

A

Retrobulbar fat and extraocular muscles

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6
Q

Malfunction of the orbicularis oculi?

A

Malfunction may lead to….

  • sagging of the lower eyelid
  • leakage of tears
  • dry eyes with the potential for corneal ulceration
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7
Q

What is a potential cause of “painless temporary loss of vision”?

A

Central retinal artery can become occluded due to transient causes such as amaurosis fugax that leads to painless temporary loss of vision in the affected eye

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8
Q

Potential cause of papilloedema?

A

Meninges & subarachnoid space extend from skull along CN II to the sclera

Raised intracranial pressure is transmitted to the meninges & subarachnoid space around CN II that slows retinal venous drainage via the central retinal vein causing papilloedema

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9
Q

What is the process of lacrimation?

A
  1. Tears produced by lacrimal gland in the upper lateral corner of the orbit
  2. Tears are secreted into the conjunctival sac
  3. From sac are continually washed across the eye by blinking (so intact function of orbicularis oculi via CN VII control is essential)
  4. The tears form a tiny lake at medial angle of eye
  5. Lacrimal caruncle lies here
  6. Tears drain via punctae to canaliculi, to lacrimal sac
  7. Drains down via nasolacrimal duct to inferior nasal meatus
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10
Q

Other name for the smooth muscle fibres of levator palpebrae superioris?

A

Superior tarsal muscle

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11
Q

Innervation of levator palpebrae superioris?

A

Smooth fibres from the sympathetics of the carotid plexus in coronary sinus

Striated fibres from CN III

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12
Q

Structures found within eyelid?

A

Skin
Levator palpebrae superioris (smooth and striated fibres)
Tarsal plate (with the tarsal gland that lubricate the lids)
Conjunctiva
Eyelashes with ciliary glands

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13
Q

Difference in the origin of cysts and sty in the eyelid?

A

Cyst: From the tarsal gland of the tarsal plate

Sty: From the cillary sebaceous glands of the eyelashes

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14
Q

Lacrimal gland innervation?q

A
  1. Superior salivatory nucleus sends preganglionic fibres in CN VII nervus intermedius
  2. These fibres travel in greater petrosal nerve & then nerve of pterygoid canal
  3. These fibres synapse in the pterygopalatine (‘hay fever’) ganglion
  4. Hitch-hike to zygomatic branch of CN V2 to reach lacrimal gland
    PS SECRETOMTOR fibers are received through zygomatic and lacrimal branches of the maxillary nerve (CNV 2) coming from the pterygopalatine ganglion. Preganglionic fibres reach the ganglion in the greater petrosal nerve arising from the facial nerve.

The SENSORY supply to lacrimal gland is by LACRIMAL nerve which is a branch of CN V1.

Essentially, the production of lacrimal fluid is stimulated by the parasympathetic impulses from the FACIAL nerve.

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15
Q

Superior and inferior rectus act only to..

A

elevate or depress the eye.
With the eyes looking directly forwards and with a slight divergent gaze, this is when the muscles are at their natural axes

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16
Q

If medial rectus draws the eye medially (convergent gaze, close-up) then both _____ & ____ _____ will augment that medial draw

A

If medial rectus draws the eye medially (convergent gaze, close-up) then both superior & inferior rectus will augment that medial draw

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17
Q

What action does superior oblique have on the eye?

A

Pulls the BACK of the eye upwards and medially therefore…..
Turns the eye inferiorly and laterally (down and out)

18
Q

What action does inferior oblique have on the eye?

A

Pulls the BACK of the eye downward and medially therefore…..
Turns the eye superiorly and laterally (down and out)

19
Q

What are the 3 axis of eye movements?

A
  1. A-P axis via lateral and medial rotation
  2. Transverse axis via elevation and depression
  3. Vertical axis via adduction and abduction
20
Q

Non synchronous movements cause…

A

Double vision = diplopia

21
Q

To go from primary position to looking right, which muscles are involved?

A

Right lateral rectus (CN VI)

Left medial rectus

22
Q

To look upwards and right, which muscles?

A

Right inferior oblique

Left superior rectus

23
Q

For both eye to look up directly, which muscles?

A

Both eyes:
Superior rectus
Inferior oblique

The medial and lateral pull cancel out, so that upwards gaze is parallel

24
Q

To look downwards and right, which muscles?

A

Right eye: Right superior oblique

Left eye: Inferior rectus

25
Q

To have both eye looking directly downwards, which muscles?

A

Inferior rectus and superior oblique of both eyes

The medial and lateral pull cancel out, so that downwards gaze is parallel

26
Q

If gaze is divergent, which muscles are working efficiently

A

Render the recti efficient and the obliques inefficient as they are slack

27
Q

If gaze is convergent, which muscles are working efficiently

A

Renders the recti inefficient and the obliques efficient

28
Q

What is the eye position when the recti are most efficient?

A

Divergent gaze to test superior and inferior recti

29
Q

What is the eye position when the obliques are most efficient?

A

Convergent gaze to test obliques.

As the medial recti has turned the gaze inwards, the inferior and superior recti are now slack

30
Q

In a divergent postion, only which muscles can elevate or depress the eye?

A

Superior and inferior recti

31
Q

which eye muscles govern the “H” of eye movement clinical testing

A

With the eye adducted, the obliques depress (superior) & elevate (inferior)
With the eye abducted, only the recti depress (inferior) & elevate (superior)

32
Q

How will a CN VI nerve lesion present when going the H test?

A

Lateral rectus won’t work

33
Q

How will a CN III nerve lesion present when going the H test?

A

Lateral rectus and superior oblique dominance

So eye will look down and out PLUS ptosis

34
Q

H movement to test eye muscles, obliques?

A

Inferior oblique: Medial and up

Superior oblique: medial and down

35
Q

H movement to test recti?

A

Lateral recti: Look laterally
Medial recti: Look medially
Superior recti: Look outward and up
Inferior recti: Look outwards and down

36
Q

Nerve lesion of CN IV H test presentation?

A

Superior oblique won’t work, unable to look medially and down

37
Q

CN III palsy eye presentation?

A

(lost ps pupil constriction)

Dilated pupil with ptosis (complete loss of levator palpebrae superioris)

38
Q

Blood supply to the orbit?

A

All from the ophthalmic branch from the internal carotid artery

  • -> Lacrimal artery branch
  • Zygomaticofacial artery
  • Zygomatico-temporal artery
  • ->Supratrochlear artery
  • Supraorbital artery
  • Anterior and posterior ethmoidal arteries
  • Dorsal nasal artery

–>Short posterior ciliary artery

–> Central artery of retina

–> Long posterior ciliary artery

39
Q

Main veins that drain the orbit?

A 
Supra orbital vein
Infraorbital vein
Superior ophthalmic vein
Vorticose veins
Angular vein

—-> Cavernous sinus and to pterygoid venous plexus

40
Q

Infection may spread to the cavernous sinus from forehead, why?

A

Note how the supra & infraorbital veins anastomose with superficial veins of the face & forehead

41
Q

If a person presents with unilateral down and out, what is the cause?

A

Oculomotor paralysis on ipsilateral side

42
Q

If person present with unilateral converged gaze, why?

A

Abducens paralysis on contralateral side

Abducens control sup oblique (down and out muscle)

MD4001 Week 3 (12 decks)

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