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OPTM 5032 - Ocular Physiology > Orbit > Flashcards

Orbit Flashcards

1
Q

The orbit attains its widest diameter where?

A

1 cm behind the orbital rim

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2
Q

The orbital roof is what shape?

A

Triangular shape

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3
Q

Orbital Roof is formed by which bones?

A

Frontal bone and lesser wing of the sphenoid bone (posterior to the frontal bone)

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4
Q

The strongest portion of the orbital rim?

A

Laterally

(zygomatic bone + zygomatic process of the frontal bone)

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5
Q

Is the lateral rim a posteriorly or anteriorly directed concavity?

A

Posteriorly

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6
Q

What is the function of the orbital rim?

A

protection from trauma

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7
Q

The orbial rim is (thick or thin) and (rounded or flat) at its (posterior or anterior) aperture?

A

Thick

Rounded

Anterior

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8
Q

Where is the lacrimal fossa found?

A

In the antero-lateral angle of the orbital roof

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9
Q

Seven bones that make up the 4 walls of the orbit?

A

Sphenoid

Frontal

Ethmoid

Maxillary

Zygomatic

Palatine

Lacrimal

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10
Q

Which bones make up both orbits?

A

Ethmoid

Sphenoid

Frontal

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11
Q

What is the bony orbit designed to do?

A

Support and provide protection to the orbital soft tissues

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12
Q

What do the soft tissues of the orbit consist of?

A

The globe and its supporting adnexa

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13
Q

The bony orbit serves as the ______ of the globe

A

Socket

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14
Q

The bony orbit is described of being made up of a ______, _____ wall, _______ , and _____ wall

A

Roof

Lateral

Floor

Medial

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15
Q

Is the oribital floor thin or thick?

A

thin

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16
Q

What bone(s) does the orbital floor mainly consist of?

A

The orbital plate of the maxillary bone

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17
Q

What is the function of the orbital floor?

A

Support to the eye and adnexal tissues and separates them from the maxiallry sinus.

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18
Q

Which part of the orbit is the weakest?

A

The orbital floor

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19
Q

The floor does not extend to the _____ and is ____ to ____ mm long

A

apex

35 - 40

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20
Q

The eyeball is about ____ inch(es)

A

1 inch

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21
Q

Why is there an increase in the rate of fractures in the orbital floor?

A

Thin bone and lack of support

22
Q

The orbital floor easily ______ to blunt trauma

A

deforms

23
Q

The floor act like a ____ ____ and blows out into the _____ _____ providing protection to the eye and tissue

A

release valve

maxillary sinus

24
Q

What symptom does the patient experience with a blow-out fracture of the orbital floor?

A

Loss of vision

Diplopia

Enophthalmos

Numb Cheek (damage to infraorbital nerve)

25
Q

What bone(s) make up the lateral orbital wall? What shape do they make?

A

Zygomatic (malar) bone anteriorly

Greater wing of the sphenoid bone posteriorly

Triangular shape

26
Q

Which portion of the orbit is smallest?

A

Medial Orbital Wall

27
Q

Is the medial wall of the orbital thin or thick?

A

thin

28
Q

Which bone(s) makes up the meidal orbit wall?

A

Lamina papyracea of the ethmoid bone

29
Q

How is the ethmoid bone supported?

A

Uniformly supported by the honeycombed structure of the ethmoid sinus bony lamina

30
Q

Which wall is fractured more often? Medial Wall or Floor of the Orbit?

A
31
Q

At birth, the anteroposterior diameter of the globe is ______ mm

A

16 mm

32
Q

When does the globe reach 90% of its adult size?

A

At 20 months of age

33
Q

At adulthood the anteroposterior diameter of the globe is?

A

~24 mm

(can vary 20-30 mm)

34
Q

What is the volume of the globe?

A

7 cm3

35
Q

What is the volume of the orbit?

A

30 cm3

36
Q

The anteroposterior diameter of the globe is?

A

~24 mm

37
Q

What is the vertical diameter of the globe?

A

~23 mm

38
Q

What is the horizontal diameter of the globe?

A

~23.5 mm

39
Q

What is proptosis?

A

The forward displacement of any object (not specific to the eyeball)

40
Q

What is exophthalmos?

A

The forward displacement of the globe

41
Q

Where is the only place the orbit can acutely expand?

A

anteriorly

42
Q

What is enophthalmos?

A

The retrodisplacement of the globe posterior into the orbit

43
Q

What is the most common cause of exophthalmos?

A

Thyroid eye disease

44
Q

What causes thyroid eye disease?

A

Caused by inflammatory reaction of an unknown cause

Glycosaminoglycans accumulate in the extraocular muscles and/or connective tissue and fat and lead to swealling

45
Q

Other causes of exophthalmos?

A

Hemangiomas

Inflammatory pseudotumors

Benign and malignant tumors

Craniostenoses and the craniofacial dysostis

severe myopia and buphthalmos may simulate exophthalmos (elognated globe)

46
Q

Enophthalmos may lead to ______exophthalmos of the contralateral eye

A

pseudo

47
Q

How is protusion usually measured?

A

From the deepest part of the lateral orbital rim to the cornal apex

48
Q

What is the most accurate exophthalmometer?

A

The Hertel exophthalmometer

49
Q

Which artery provides the primary blood supply to the orbit?

A

opthalmic artery

50
Q

orbital veins (do or do not) parallel orbital arteries, except _____ and ____ veins

A

Do Not

lacrimal and ethmodial veins

51
Q

Do orbital veins possess valves?

A

No

OPTM 5032 - Ocular Physiology (9 decks)

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