THE ORBIT Flashcards
What supports and provide protection to the orbital soft tissues?
The Bony Orbit
What makes up the bony orbit?
The roof, lateral wall, floor and medial wall
What bones make up the 4 walls
Sphenoid, Frontal, Ethmoid, Maxillary, Zygomatic, Palatine, Lacrimal
Which bones are common to both orbits
Sphenoid, Frontal, Ethmoid
What is the strongest portion of the orbital rim
zygomatic bone and zygomatic process of the frontal bone
What is the downside to having a concavity?
makes the eye prone to injury
what is the pros to having concavity
increases lateral visual field
What is the purpose of the orbital rim
protection from trauma
The orbital roof has a _____ shape?
triangular
What bones make up the orbital roof
Frontal, lesser wing of the sphenoid bone (posterior to frontal bone)
The lacrimal fossa holds what?
the lacrimal gland
T/F the lacrimal gland can’t be seen in the shallow orbit
False; don’t misdiagnose as a tumor
T/F The orbital rim is thin and mainly consists of the orbital plate of the maxillary bone
false; orbital floor. the orbital rim is thick and rounded at its anterior aperture
T/F The orbital floor is the strongest orbital wall
false; weakest
Orbital floor gives support to the eye and the ________ tissues and separates them from the ______sinus
adnexal; maxillary
T/F The floor extends to the apex
false
Orbital floor is \_\_\_\_\_\_ to \_\_\_\_\_ mm long a) 35-50 b)15-40 C)20-40 D)35-40
35;40
T/F the floor easily deform to blunt trauma
T
______ bone and lack of support _____ the rate of fractures
thin; increases
Where does the floor blow out into in a blowout fracture
maxillary sinus
Why does the floor blow into the maxillary sinus
it provides protection to the eye and tissues
Patient has a BOF with loss of vision why?
Retinal detachment, retinal tear and/or optic nerve damage
Patient has a BOF with diplopia why?
Because of muscle entrapment
Patient has a BOF with enophthalmos why?
loss of support
Patient has a BOF with numb cheek why?
for damaged to the infraorbital nerve
What is enophthalmos?
sunken eye
When will a BOF be repaired with surgery
restricted strabismus, enophthalmos
When would you cause a BOF
Thyroid eye disease
The lateral orbital wall is form by ______ and ______ bones and _______ in shape
zygomatic malar; greater wing of sphenoid bone; triangular
The medial orbital wall is _____ and _______
smallest; thin
A ______ _______ of the ethmoid bone is extremely thin
Lamina papyracea
What protects the medial wall from being fractured
the honeycomb structure of the ethmoid sinus bony lamina
Which wall is fractured most often
Orbital floor
The globe reaches \_\_\_\_\_ of its adult size when an infant is \_\_\_\_\_ of age a) 90% 10months b)90% 20 months C)80% 10 months D)80% 20 months
90%; 20 months
At birth the \_\_\_\_\_\_ diameter of the globe is \_\_\_\_\_ mm. In adulthood it is \_\_\_\_ mm a) 16 , 24 b)10, 24 C)16, 20 D)16, 10
anteroposterior;
A)16; 24
What are the three factors that affect the size of globe?
refractive error (myopia), gender (males > females), ethnicity (Chinese smallest)
The volume of the globe is \_\_\_\_\_cm^3 a) 7 b)10 C)9 D)8
7
The volume of the orbit is \_\_\_\_\_cm^3 a) 60 b)40 C)30 D)10
30
The vertical diameter of the globe is \_\_\_\_\_ and the horizontal diameter is \_\_\_\_\_ a) 23mm, 24 mm b)23mm, 25 mm C)23mm, 26 mm D)23mm, 23.5 mm
23 mm; 23.5 mm
What is exophthalmos
forward displacement of the globe
Why can you not use proptosis to describe exophthalmos
both are a forward displacement but proptosis is of any object and is not specific to the eyeball
Why does any displacement of the eye cause the globe to move forward?
the only place the orbit can acutely(suddenly)expand is anteriorly
As you age what decreases and what does it cause
fat content and it causes enophthalamos
What is the most common cause of unilateral and bilateral exophthalamus in adults
Thyroid eye disease
T/F Can thyroid eye disease be only unilateral
F; it is unilateral or bilateral
What accumulates in the EOM’s and/or connective tissue and fat and leads to swelling in thyroid eye disease
Glycosaminoglycans (GAG)
What is craniofacial dysostosis and what can it cause
Defect in the normal ossification of fetal cartilages; exophthalmos
What is a hemangioma and what can it cause
an abnormal buildup of blood vessels ; exophthalmos
What is craniostenosis and what can it cause
fault (premature) in fusing of bones; exophthalmos
What is buphthalmos and what can it cause
eye is stretched for some reason, all structures become longer; exophthalmos
T/F severe hyperopia and buphthalmos may stimulate exophthalmos
False, severe myopia and buphthalmos may stimulate exophthalmos
______ may lead to _____ exophthalmos of the contralateral eye
enophthalmos; pseudo
What faults or defect in bones can cause exophthalmos
craniostenosis, craniofacial dysostosis
What type of tumors can cause exophthalmos
inflammatory pseudotumors, benign and malignant tumors
What abnormal blood vessel buildup can cause exophthalmos
hemangioma
The amount of protrusion of the normal eye can be important _______ ________
clinical marker
Where is the protrusion typically measured from
deepest part of the lateral orbital rim to the corneal apex
What is the most accurate device in measuring protrusion
hertel exophthalmometer
T/F a simple ruler cannot be used to measure protrusion
F; it can be used
What three types of collagen make up the orbital connective tissue and describe them
CT I - structural integrity
CT III - adhesion between connective tissue and adipocytes
CT IV - basement membranes of connective tissue vessels
What type of cells make up the orbital tissue
Fibroblasts and endothelial cells
_____ percent of individuals have the _______ artery as the primary blood supply to the orbit. ______ percent of individuals have the _____ artery contribute equally through an accessory to ______ artery
96; Ophthalmic artery; 3; middle meningeal artery; ophthalmic
T/F Orbital veins and arteries follow the same course in the system
F; the follow different course
Orbital veins _____ parallel orbital arteries
do not; except lacrimal and ethmoidal veins
T/F Orbital veins do not posses valves
T; valves prevent backflow
