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Ocular Physiology > Orbit > Flashcards

Flashcards in Orbit Deck (51)
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1

what are the 4 areas of the orbit

roof, lateral wall, floor and medial wall

2

what is the purpose of the orbit

to support and provide protection to the orbital soft tissues (globe and adnexa)

3

how many bones make up the surrounding walls

7

4

name the 7 bones that make up the 4 walls of the orbit

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

5

which bones are common to both orbits

ethmoid, sphenoid, and frontal

6

what is the purpose of the orbital rim

protection from trauma

7

what is the strongest portion of the orbit

the lateral portion of the orbital rim (zygomatic bone and zygomatic process of frontal bone)

8

why does the lateral rim have a concavity posteriorly directed

the increase the visual field, but the eye is prone to injury

9

what shape is the orbital roof

a triangular shape

10

what bones form the orbital roof

frontal bone and lesser wing of the sphenoid bone

11

where is the lacrimal fossa found

in the antero-lateral angle of the orbital roof

12

what is the thinnest portion of the orbit

the floor

13

what makes up the orbital floor

orbital plate of the maxillary bone

14

what is the purpose of the orbital floor

the support the eye and adnexal tissues, separate them from the maxillary sinus

15

how long is the orbital floor

35-40mm (doesn't extend to the apex)

16

during a blow out fracture, where does the eye blow out to

the maxillary sinus

17

why does the orbital floor break in a blow out fracture

it acts as a release valve to decrease orbital pressure and blows out to provide protection to the eye and adnexa

18

what symptoms might a person have with a blow out fracture

loss of vision, diplopia, enophthalmos, or a numb cheek

19

what nerve damage would cause the cheek to go numb in an orbital blow out fracture

damage to the infraorbital nerve (CN 7 facial)

20

why might someone have diplopia following a blow out fracture

it may cause restrictive strabismus (recti muscles get trapped)

21

what is enophthalmos

where the eye is sunken in and sometimes downward

22

why might a doctor purposely break the orbital floor

if they have thyroid eye disease (graves disease) to allow for the exophthalmos eye to have more room

23

what bones form the lateral wall and what shape do they make

zygomatic (anteriorly) and greater wing of sphenoid bone (posteriorly)- triangular shape

24

which wall of the orbit is the smallest

the medial wall

25

what bones make up the medial wall

Lamina Papyracea of the ethmoid bone, supported by the honeycomb structure of ethmoid sinus bony lamina

26

what protects the medial wall from being fractured

because it is being supported by the honeycomb structure of the ethmoid sinus bony lamina

27

what is the anterior-posterior diameter of the globe at birth

about 16mm

28

when does the globe reach 90% of its adult size

at 20 months (or about 2 years old)

29

what is the anterior-posterior diameter of an adult globe

about 24mm (varies from 20-30mm)

30

what may cause the anterior-posterior diameter of the adult globe to vary

refractive error (most common), gender, ethnicity