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Ocular Anatomy - Exam 1 > Exam 1 - 002 Orbit and Paranasal Sinuses > Flashcards

Exam 1 - 002 Orbit and Paranasal Sinuses Flashcards

1
Q

Bones of the orbit

A 
maxillary
palatine
frontal
sphenoid
zygomatic
ethmoid
lacrimal
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2
Q

Relationship of the medial walls of the orbit

A

 Roughly parallel

 About 25 mm apart

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3
Q

Relationship of the lateral walls of the orbit

A

About 90 degrees from each other

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4
Q

Angle where the lateral and medial walls meet at the apex of the orbit

A

45 degrees

makes the orbit pyramidal in shape

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5
Q

Location of the widest part of the orbit

A

about 15 mm behind the orbital margin

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6
Q

Depth of the orbit

A

45 mm

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7
Q

Bones of the Roof

A 
**The roof slope down from front to back
Frontal bone 
•	orbital plate
•	anterior part
•	Thin so can get blown out easily
Lesser wing of the sphenoid bone
•	Posterior part
•	Much thicker than the frontal bone
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8
Q

Landmarks of the roof

A

•Lacrimal fossa
o Depression in the frontal bone
o In the superior temporal position behind the lateral aspect of the superior orbital margin (so anterior)
•Fovea trochlearis (AKA trochlear fossa)
o Medial depression on the frontal bone
o About 4 mm behind the medial aspect of the superior orbital margin
o Houses the cartilaginous pulley (trochlea) for the tendon of the superior oblique muscle

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9
Q

Features of the lateral wall

A

 Roughly triangular
 Thickest orbital wall
 Separated from the roof of the orbit by the superior orbital fissure
 Separates orbit from temporal fossa (and the temporalis muscle) anteriorly
 Posteriorly the greater wing of sphenoid separates orbit from the middle cranial fossa

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10
Q

Bones of the lateral wall

A

•Greater wing of the sphenoid bone
o Posterior 2/3
•Zygomatic bone
o Anterior 1/3

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11
Q

Landmarks of the lateral wall

A

•Lateral orbital tubercle
o On the orbital surface of zygomatic bone
o Located just within the lateral orbital margin at its midpoint
o Attachment site for several structures
•Zygomatico-orbital foramen
o Opening in zygomatic bone
o Carries zygomatic nerve and blood vessels
o Leads to zygomaticotemporal and zygomaticofacial foramen

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12
Q

Features of the medial wall

A

 Rectangular

 THINNEST orbital wall

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13
Q

Bones of the medial wall

A 
•Maxillary bone
•Lacrimal bone
•Lamina papyracea of ethmoid bone (largest part of the medial wall)
o	Paper thin
o	Separates orbit from ethmoid air cells
•Body of the sphenoid
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14
Q

Landmarks of the medial wall

A
  • Fossa for the lacrimal sac

* Nasolacrimal canal

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15
Q

Fossa for the lacrimal sac

A

o Formed by the maxillary and lacrimal bones
o Anterior and posterior borders are the lacrimal crests
 Anterior lacrimal crest on maxillary bone
 Posterior lacrimal crest on lacrimal bone
o Contains the lacrimal sac

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16
Q

Nasolacrimal canal

A

Bony canal within the maxilla that is continuous with the fossa for the lacrimal sac
o Below the level of the orbital floor
o Leads inferiorly into the inferior meatus of the nasal cavity
o Contains the nasolacrimal duct

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17
Q

Features of the floor of the orbit

A

 Triangular
 Separated from the lateral wall by the IOF
 Frequently fractured due to the thinness of the floor and presence of the infraorbital groove and canal where the orbital floor is the thinnest

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18
Q

Bones of the floor of the orbit

A 
•	Maxillary bone
o	Largest part of the orbital floor
•	Zygomatic bone
•	Palatine bone
o	Smallest part of the orbital floor
o	Most posterior in the floor
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19
Q

Landmarks of the floor of the orbit

A

• Infraorbital groove, canal and foramen
• Nasolacrimal canal
o Anterior-medial on the floor of the orbit

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20
Q

Infraorbital groove

A

o Groove runs forward from the IOF
o Canal is formed when the groove acquires a roof with the maxillary bone
o Foramen is where the canal opens onto the face
o Transmits the infraorbital nerve, artery and vein

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21
Q

Anatomical relationship of the roof of the orbit

A

 Can damage the frontal lobe and meninges of the brain
 Frontal sinus cyst can enlarge into the thin roof of the orbit
 Fracture of the superior orbital margin can damage the trochlea leading to superior oblique paralysis
 Lacrimal gland can be damaged

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22
Q

Which two walls of the orbit are the weakest?

A

Floor and medial wall

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23
Q

Inferior Orbital Fissure

A

 Separates lateral wall and floor of the orbit
 Lies between the greater and lesser wings of sphenoid
 Connects
• Pterygopalatine fossa and infratemporal fossa to the orbit
 Transmits
• Infraorbital artery and vein
• Infraorbital nerve
• Zygomatic nerve
o Postganglionic parasympathetic fibers to the lacrimal gland (hitch-hiking)
• Inferior Ophthalmic vein

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24
Q

Supraorbital Foramen

A

AKA supraorbital notch
Transmits
• Supraorbital artery, vein and nerve

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25
Q

Anterior Ethmoidal foramen

A

Transmits

• Anteriror ethmoidal artery and nerve

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26
Q

Posterior Ethmoidal Foramen

A

Transmits

• Posterior ethmoidal artery and nerve

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27
Q

Zygomatic Foramina

A 
Zygomatico-orbital foramen
     •Transmits
        oZygomatic nerve
Zygomaticofacial foramen
     •	Transmits
          o	Zygomaticofacial nerve
Zygomaticotemporal foramen
     •	Transmits
          o	Zygomaticotemporal nerve
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28
Q

Orbital Rim

A

the sharp edge of the orbital opening, which is the peripheral border of the base of the pyramid-shaped orbit

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29
Q

Orbital Margin

A

o It is quadrangular in shape with rounded corners
o The dimensions of the margin (height, width, depth)
 Horizontal diameter – 40 mm
 Vertical diameter – 35 mm

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30
Q

Bones of the superior orbital margin

A
  • Superior orbital margin

* Frontal bone

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31
Q

Bones of the inferior orbital margin

A
  • Zygomatic bone

* Maxillary bone

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32
Q

Bones of the lateral orbital margin

A
  • STRONGEST and most exposed part of margin
  • Frontal bone
  • Zygomatic bone
  • Weakest part is at the suture between the frontal and zygomatic bones
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33
Q

Bones of the medial orbital margin

A
  • Maxillary bone

* Frontal bone

34
Q

Why is the orbital margin the strongest part of the orbit?

A

 All three bones are usually thick at the orbital margin

 The sutures by which the bones connect are extensive

35
Q

What is a blow out fracture?

A

o Refers to the rupture of the orbital bones
o The margin will remain intact but the bones will fracture away from the site of impact
 The orbital plates within the orbit are relatively thin and easily broken, which leads to a blow out fracture
o Usually occurs when an object larger than the orbit strikes the orbital margin
 Causes compression of the orbital contents and a sudden increase in intraorbital pressure
 The shock wave of this travels through the site of impact and:
• Causes a fracture in one of the orbital walls at one of the weaker points in the bone
• May cause expulsion of the soft tissue through the fracture site
o The blow out fracture is a safety mechanism to prevent the rupture of the eyeball

36
Q

Most common sites of a blowout fracture?

A

 Maxillary bone by the infraorbital groove

 Lamina paprycea of ehtmoid

37
Q

Symptoms of a blow out fracture

A

 Black eye (ecchymosis)
 Loss of sensation along the distribution of nerves on the floor or medial wall of orbit
 Diplopia, due to restriction of ocular motility
 Enophthalmos – posterior displacement of the eye in the orbit
• Leads to a smaller palpebral fissure on the affected side

38
Q

Treatment of a blowout fracture

A
  • Antibiotics
  • Steroids to reduce orbital edema if present
  • Resect perioorbita
  • Repair fracture using bone grafts, synthetic materials like silicone or MEDPOR
39
Q

Orbital openings

A 
o Optic Canal
	Connects orbit to middle cranial fossa
oSuperior Orbital Fissure
	Connects the middle cranial fossa to the orbit
o	Inferior Orbital Fissure
	Connects PP fossa
40
Q

What does the optic canal transmit

A

Optic nerve

Ophthalmic artery

41
Q

What does the Superior Orbital Fissure transmit?

A 
	Lacrimal N (CN V1)
	Frontal N (CN V1)
	Trochlear N (CN IV)
	Superior and inferior division of oculomotor nerve (CN III)
	Nasociliary N (CN V1)
	Abducens N (CN VI)
	Superior Opthalmic V
	Inferior Ophthalmic V
42
Q

What does the inferior orbital fissure transmit?

A

???

43
Q

What is the periorbita?

A

It is the orbital periosteum
 Covers all of the bones of the orbit, the entire inner surface of the orbit
 Contains nerves and blood vessels that can penetrate the bone and provide innervation and nutrients
 Bands of CT that extend from the periorobita to CT surrounding the eyeball provide structural support for the eyeball
• Has extensions to hold the trochlea in place, enclose the lacrimal sac and the lacrimal gland
 Provides temporary resistance to the spread of infections and tumors from paranasal sinuses into the orbit

44
Q

Attachments of the periorbita?

A 
	Firmly attached
•	Orbital margin
•	Suture lines
•	Foramina
•	Fissures
•	Lacrimal fossa
	Loosely attached
•	Everywhere else
•	Can be easily detached by accumulations of blood or pus from trauma, which will push on the eyeball and other orbital contents
45
Q

What is the periorbita directly continuous with?

A 
	Posteriorly
•At the optic canal
•Continuous with the periosteal layer of the dura surrounding the optic nerve
	Anteriorly
•Periosteum of skull bones of the face
o	Zygomatic bone
o	Frontal bone
o	Maxillary bone
•Orbital septum
46
Q

What is the orbital septum?

A

o Connective tissue membrane that extends from the orbital margin towards the tarsal plates of the eyelids (through the center of the eyelid)
o Separates the contents of the eyelids from the orbital contents

47
Q

Insertions of the orbital septum

A

 Upper eyelid
• Aponeurosis of levator palpebrae superioris, NOT into the superior tarsal plate
 Lower eyelid
• Orbital septum fuses with the fascia of the inferior tarsal muscle and together they insert into the inferior border of the tarsal plate

48
Q

Functions of the orbital septum

A

 Anatomic barrier to infection, hemorrhage and edema
 Prevents the spread of blood or inflammation from the eyelid to the orbit
 Holds orbital fat in position
 MAIN FUNCTION is to prevent infections from entering the orbit

49
Q

Preseptal cellulitis

A
  • generalized inflammation or infection of the tissues of the eyelid anterior to the orbital deptum
  • Most commonly occurs secondary to a staphylococcal or streptococcal bacterial infection in the eyelid OR the extension of a paranasal sinus infection
  • The infection must involve the surrounding eyelid tissue
50
Q

Signs/symptoms of preseptal cellulitis

A 
o	Eyelids appear red and swollen, warm and may be painful or tender to the touch 
o	Patient may be unable to open eyelid due to eyelid edema
o	NO:
	No disturbance in visual acuity
	No proptosis
	No pain with eye movement
	No restriction of eye movement
	Pupils are normal
51
Q

Treatment of preseptal cellulitis

A

Oral antibiotics

52
Q

Orbital Cellulitis

A

• generalized inflammation or infection of the soft tissues posterior to the orbital septum
• Most commonly occurs secondary to a staphylococcal or streptococcal bacterial infection
o I.e. orbital trauma, paranasal sinus infections, complication of orbital or paranasal surgery, tooth infection spreading, penetrating injury, etc
o Most common cause is paranasal sinus infections in children

53
Q

Signs/Symptoms of orbital cellulitis

A 
o	Eyelid edema
o	Redness and distension (swelling and tightness) of the lid and surrounding orbital skin
o	Difficulty opening the eyelid
o	Significant pain upon palpation
o	Swollen conjunctiva (chemosis)
o	Conjunctival vessels congested
o	Fever
o	There IS proptosis (forward displacement of the eyeball)
o	Pain on eye movement
o	Restriction of eye movement
54
Q

Which is more serious - preseptal or orbital cellulitis?

A

Orbital cellulitis
• Considered a serious medical issue because if left untreated it could lead to severe vision-threatening complications and life threatening complications (like meningitis, intracranial abscesses or cavernous sinus infections)

55
Q

Treatment for orbital cellulitis

A

Hospitalization to receive antibiotics intravenously (IV)

56
Q

What nerves should pierce the orbital septum?

A

 Nerves and vessels that are trying to reach the eyelids, face, forehead that do NOT pass through a foramen or notch

57
Q

Annulus of Zinn

A

AKA common tendinous ring
 The thickening of the periorbita posteriorly around the optic canal and central part of the superior orbital fissure
 Located at the apex of the orbit
 Oval tendinous ring
 Attaches to the lesser and greater wings of the sphenoid
 Surround the optic canal and a portion of SOF
 Forms the origin for tendons of the four rectus muscles (LR, MR, SR, IR)

58
Q

What structures pass through the Superior orbital fissure and then ABOVE the common tendinous ring?

A 
Mneumonic: LF STUNALI
•	Frontal nerve – in the orbit is when it divides into supraorbital and supratrochlear nerves
•	Trochlear Nerve (CN IV)
•	Lacrimal N
•	Superior Ophthlamic Vein
59
Q

What structures pass through the Superior orbital fissure and then THROUGH the common tendinous ring?

A
  • Superior Division of CN III
  • Inferior Division of CN III
  • CN VI
  • Nasociliary N
60
Q

What structures pass through the Superior orbital fissure and then BELOW the common tendinous ring?

A

Inferior Ophthalmic Vein

61
Q

What structures pass through the optic canal and then THROUGH the common tendinous ring?

A

Optic Nerve

Ophthalmic artery

62
Q

Spaces lying above the orbit

A

Anterior cranial fossa

(In some people) frontal sinus

63
Q

Spaces lying medial to the orbit

A

 Ehtmoidal sinuses
 Sphenoid sinus
 Nasal cavity

64
Q

Spaces lying below the orbit

A

maxillary sinus

65
Q

Spaces lying posterior to the orbit

A

Middle cranial fossa

66
Q

Paranasal sinus locations

A

 Located in four bones of the skull

67
Q

Frontal sinuses

A

Right and Left
• Superior to the orbits in the frontal bone
• Behind the supracilliary arches
• MAY extend posteriorly into the orbital plate of the frontal bone allowing infections to spread through the thin orbital roof into the orbit or anterior cranial fossa

68
Q

Frontal sinus relationships to other structures

A

o Posterior – anterior cranial fossa
o Superior – anterior cranial fossa and meninges of the frontal lobe (if frontal sinus is in orbital plate)
o Inferior-medial – drains into the middle meatus

69
Q

Ethmoid Air cells/sinuses

A

Right and left
• Medial to the orbits
• Separated by lamina papyracea

70
Q

Relationship of anterior ethmoid air cells to other structures

A 
Anteriorly - nothing
Posteriorly - Middle air cells
Superiorly - anterior cranial fossa and meninges of the frontal lobe
Medially - middle meatus
laterally - orbit
71
Q

Relationship of Middle ethmoid air cells to other structures

A 
Anteriorly - anterior ethmoid air cells
Posteriorly - posterior air cells
Superiorly - anterior cranial fossa and meninges of the frontal lobe
Medially - middle meatus
laterally - orbit
72
Q

Relationship of posterior ethmoid air cells to other structures

A 
Anteriorly - middle air cells
Posteriorly - sphenoid sinus
Superiorly - anterior cranial fossa and meninges of the frontal lobe
Medially - superior meatus
laterally - orbit
73
Q

Sphenoid sinuses

A

Right and left

• Posterior and medial to the orbit

74
Q

Relationship of sphenoid sinus to other strucutres

A 
o	Pituitary gland superior
o	Cavernous Sinuses laterally
o	Optic nerves as they exit the orbit
o	Posterior ethmoid air cells anteriorly
o	Orbit laterally from the sinus
o	Posterior cranial fossa
75
Q

Maxillary Sinuses

A

Right and Left
• In the maxillary bone below the orbital floor and inferolateral to the nasal cavities
• Floor is formed by the alveolar bone of the upper teeth

76
Q

Relationship of maxillary sinuses to other structures

A

o Superior – orbit
o Medial – drains into middle meatus
o Inferior – teeth and gums

77
Q

Computerized tomography scan (CT scan)

A

o CT scans use ionizing radiation in the form of x-rays, creating an image as if the examiner was standing at the foot of the bed and looking towards the head of a patient lying down
 The machine measures the amount of radiation that passes through the body, reconstructing an image
 Dense tissues block the passage of x-rays (like bone, so it appears gray) vs. less dense tissues (like air or fluids, which appear black)

78
Q

What can you see with CT scans and when should you use them?

A

 EOMs, optic nerves and major blood vessels can be distinguished in conjunction with bone on CT scans
 Orbital tumors can be well visualized
• The orbit has thin bones and the orbital fat provides good background contrast so dye is not needed
• Tumors appear whitish, especially those containing calcium
 Locations to use when you suspect
• Bone fractures
• Foreign bodies in the orbit (especially metallic structures)
• Orbital tumors
don’t use on pregnant women

79
Q

MRI

A

 Creates an image as if the examiner was standing at the foot of a bed and looking up at the head (left side of the body is on the right side of the image)
 Uses a magnetic field to align the hydrogen atoms present in water and fat in the body tissues (shows a proton/water? Gradient)
• CAN NOT USE IF METAL IS ANYWHERE IN THE BODY
• Then uses low frequency radio waves whose energy is absorbed by the hydrogen ions
• When the radio waves are turned off, the hydrogen atoms return to their original position, emitting the energy they had absorbed as weak radio signals that are stored and reconstructed by the MRI computer

80
Q

What can be seen and when should you use an MRI?

A

 Soft tissues composed of a large amount of hydrogen atoms are well defined (like the brain and spinal cord)
• Gray matter of the brain is gray, white matter and fat are white, CSF or water is black, bone and air are black
• Compact bone plates are black but the bone marrow is white
 When to use an MRI
• Higher resolution imaging of the nervous system than CT scans
• Brain tumors
• Neurologic diseases of the brain (like multiple sclerosis)

Ocular Anatomy - Exam 1 (5 decks)

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