Ocular W1

(orbital) fat

substance that serves as cushioning in the orbit and wraps around the EOMs, nerves, and blood vessels

displacement from normal position

Since there is a small amount of space between orbital walls and the eyeball, tumors or masses expanding in the orbit would have what effect on the eyeball?

frontal, zygomatic, maxillary, ethmoid, sphenoid, lacrimal, palatine

What are the seven bones that form the walls of the orbit?

2, 2, 3, 4, all have the sphenoid except the floor

How can you remember how many bones make up each wall of the orbit? (Hint: start at the top, then lateral, etc.)

frontal

zygomatic

maxillary

ethmoid

sphenoid

lacrimal

palatine

90

The lateral walls of the orbit are roughly how many degrees apart?

45

What is the value of the angle where the lateral and medial walls meet at the orbital apex? (resembles a pyramid, about 18 mm apart)

lateral, roof, floor

Which walls of the orbit are roughly triangular in shape?

medial

Which wall of the orbit is roughly rectangular in shape?

15 mm behind the margin

Where is the widest point of the orbit? (Hint: NOT at margin)
**approximately lines up with equator of the orbit

45 mm

What is the depth of the orbit?

frontal, lesser wing of sphenoid

What bones form the roof of the orbit?

frontal

Which bone forms the MAJORITY of the orbital roof?

lesser wing of sphenoid

Which bone forms the SMALLER posterior portion of the roof?

frontal

Which bone of the orbital roof is much thinner and is therefore subject to "blow-in fractures" as well as penetrating injuries: frontal or sphenoid?

roof (specifically in the frontal bone)

Where do blow-in fractures most commonly occur?

anterior cranial fossa

Which division of the skull lies directly superior to the orbit?
**except for anterior part, where the frontal sinus is above the orbit

lacrimal fossa

depression which lies in the superior temporal position on the frontal bone, just behind the superior orbital margin; the lacrimal gland is found here!

fovea trochlearis, trochlear fossa

two names for the small medial depression on the frontal bone behind the medial aspect of the superior orbital margin; the cartilaginous pulley for the tendon of the superior oblique muscle lies here in the anterior-medial portion of the orbital roof

frontal

On which bone are both the lacrimal fossa (for the lacrimal gland) and the fovea trochlearis found?

true

True or false: The fovea trochlearis is located more medially, and the fossa for the lacrimal gland is temporal.

fovea trochlearis

lacrimal fossa

superior oblique

If the roof of the orbit were damaged in such a way that affected the cartilage pulley in the fovea trochlearis, what muscle would be affected?

dura mater

Parts of the orbital roof can actually be absorbed in old age, bringing what specific part of the frontal lobe into contact with the periosteum of the orbit?

frontal sinus

Anteriorly, the orbital plate of the frontal bone may contain a portion of what structure?

**an enlarging mucocele in this could expand into the orbit through the thin roof, causing an infection to potentially spread superiorly to the frontal lobes and their meninges or inferiorly to the orbit

zygomatic, greater wing of sphenoid

What bones form the lateral wall of the orbit?

zygomatic

Which bone forms the anterior third of the lateral wall of the orbit?

greater wing of sphenoid

Which bone forms the posterior two-thirds of the lateral wall of the orbit?

lateral wall

Which orbital wall is the thickest?

lateral orbital tubercle

small elevation/bump on the orbital surface of the zygomatic bone, located just within the lateral orbital margin at its midpoint; serves as the attachment site for several structures

zygomatic

On which bone is the lateral orbital tubercle found?

zygomaticoorbital foramen

opening in the zygomatic bone that carries the zygomatic nerve and blood vessels
**some people have 1, some have 2 (each one opens up into either the zygomaticofacial or zygomaticotemporal)

zygomaticoorbital foramen

transmits zygomatic nerve

zygomaticofacial foramen

transmits namesake nerve

zygomaticotemporal foramen

transmits namesake nerve

temporal

Anteriorly, the lateral wall separates the orbit from what region of the skull? (Hint: contains the temporalis muscle)

middle cranial fossa

Posteriorly, the greater wing of the sphenoid separates the lateral wall of the orbit from what division of the skull?

superior orbital fissure

What separates the lateral wall of the orbit from the roof?

maxillary, lacrimal, ethmoid, body of sphenoid

What bones form the medial wall of the orbit? (from anterior to posterior)

medial

Which orbital wall is the thinnest?

mostly consists of the very thin lamina papyracea (of the ethmoid)

Why is the medial wall of the orbit the thinnest wall?

orbital cellulitis

Infections in both ethmoid air cells and the sphenoid sinus can easily spread to the orbit via the lamina papyracea, causing what condition?

fossa for the lacrimal sac

depression formed by the maxillary & lacrimal bones the is bounded by the anterior & posterior lacrimal crests; contains the lacrimal sac

maxillary, lacrimal

What two bones form the fossa for the lacrimal sac?

maxillary

Which bone contains the ANTERIOR lacrimal crest?

lacrimal

Which bone contains the POSTERIOR lacrimal crest?

nasolacrimal canal

bony canal within the maxilla that is continuous superiorly with the fossa for the lacrimal sac; lies below the orbital floor and leads inferior into the inferior meatus of the nasal cavity, which contains the nasolacrimal duct

lies anterior-medial on the floor

true

True or false: Both the lacrimal sac and nasolacrimal duct are considered "soft tissue" and are lined by an epithelium.

lamina papyracea

specific part of the ethmoid that makes up the medial wall

fossa for the lacrimal sac

anterior lacrimal crest, maxillary

structure, what bone it's found on

posterior lacrimal crest, lacrimal

structure, what bone it's found on

nasolacrimal canal

maxillary, zygomatic, palatine

What bones form the floor of the orbit?

maxillary

What bone forms the LARGEST portion of the orbital floor?

palatine

What bone forms the SMALLEST portion of the orbital floor?

inferior orbital fissure

leads into the infraorbital groove

infraorbital groove

leads into the infraorbital canal

infraorbital canal

leads to the infraorbital foramen
**transmits namesake nerve, artery, & vein

maxillary

The infraorbital canal is located within which bone?

maxillary sinus

What lies beneath most of the orbital floor?

orbital cellulitis

Maxillary sinus infections can easily invade the orbit, leading to what condition?

proptosis

A maxillary sinus tumor could extend superiorly into the orbit causing what condition if the tumor ends up in the orbit behind the eyeball?

inferior orbital fissure

The nasolacrimal canal lies anterior-medial on the floor, which is separated from the lateral wall by what?

inferior orbital fissure

Where is the orbital floor the thinnest? (i.e. Where is a fracture most likely to occur in the floor?)

horizontal

Does the orbit have a greater horizontal or vertical diameter?

frontal, maxillary, zygomatic

What three bones make up the orbital margin (rim)?

frontal

What comprises the superior orbital margin?

supraorbital notch (or foramen)

structure located just medial to the center of the superior orbital margin that transmits its namesake nerve, artery, & vein

frontal, zygomatic

What comprises the lateral orbital margin?

zygomatic, maxillary

What comprises the inferior orbital margin?

maxillary, frontal

What comprises the medial orbital margin?

lateral
(though its weakest part is at the suture between the frontal and zygomatic bones)

Which part of the orbital margin is the strongest?

blow out fracture

Even though the orbital margin is very thick, when someone receives a heavy blow to the margin, the bones of the orbit may fracture "away" from the margin. What is this called?

**refers to the rupture of the orbital bones

floor

Where do blow-out fractures most commonly occur? (i.e. which wall)

groove part of maxilla, lamina papyracea of ethmoid

What are the two most common sites for orbital fractures?

B

The most common site for a blow-out fracture following trauma involves which of the following orbital bones?
A. zygomatic
B. maxillary
C. ethmoid
D. lacrimal
E. sphenoid
F. frontal
G. palatine

IOP

Ultimately, the orbital walls may experience a blow-out fracture due to a sudden increase (and resulting shockwave) in what value?

black eye (ecchymosis), loss of sensation, diplopia, enophthalmos

What are four symptoms of a blow-out fracture?

restriction of ocular motility
(due to EOM damage by medial wall or floor and entrapment of EOMs within fracture site)

Why does diplopia occur from a blow-out fracture?

posterior displacement of eye in orbit

Why does enophthalmos occur from a blow-out fracture?

lesser wing of sphenoid (therefore the roof)

Where is the optic canal located? (What bone?)

orbit, middle cranial fossa

What two larger spaces does the optic canal connect?

optic nerve, ophthalmic artery

What two things does the optic canal transmit?

roof, lateral

What two walls of the orbit does the superior orbital fissure separate?

lesser and greater wings of sphenoid

What two bones of the orbit does the superior orbital fissure separate?

orbit, middle cranial fossa

What two larger spaces does the superior orbital fissure connect?

lacrimal (from V1), frontal (from V1), nasociliary (from V1), trochlear (IV), oculomotor (III), abducens (VI)

What six NERVES does the superior orbital fissure transmit?

superior and inferior ophthalmic veins

What two VESSELS does the superior orbital fissure transmit?

common tendinous ring

fibrous structure that the rectus muscles arise from

lacrimal nerve, frontal nerve, superior ophthalmic vein, trochlear nerve

What passes ABOVE the common tendinous ring? (that also goes through the SOF)

upper branch of oculomotor nerve, nasociliary nerve, abducens nerve, lower branch of oculomotor nerve

What passes THROUGH the common tendinous ring? (that also goes through the SOF)

inferior ophthalmic vein

What passes BELOW the common tendinous ring? (that also goes through the SOF)