11 Orbit Anatomy

Question 1

Avg volume of orbit

Answer 1

30 cm3

Question 2

Avg depth of orbit

Answer 2

40-50 mm

Question 3

Whats unique about anatomy of Asian eyelid

Answer 3

levator muscle lacks attachment to pretarsal skin resulting in absent pretarsal fold

Question 4

What divides the lacrimal gland into 2 lobes

Answer 4

levator aponeurosis

Question 5

What provides static support to lower lid

Answer 5

tarsal plate and its assoc medial and lateral canthal tendons

Question 6

What provides dynamic support to lower lid

Answer 6

adhesion of pretarsal portion of orbicularis to tarsal plate

Question 7

What structure in lower lid is analogous to levator aponeurosis of upper lid

Answer 7

capsulopalpebral fascia

Question 8

what are the lower eyelid retractors

Answer 8

capsulopalpebral fascia and inferior tarsal muscle

Question 9

What lines the posterior surface of eyelid

Answer 9

palpebral conjunctiva

Question 10

what creates gray line in lid margin

Answer 10

muscle of riolan

Question 11

what does the gray line divide

Answer 11

anterior and posterior lamella

Question 12

What is the origin of the superior tarsal muscle (of Muller)

Answer 12

Deep side of the levator palpebrae superioris

Question 13

What structure forms the medial canthal tendon

Answer 13

superficial head of the pretarsal fibers of the orbicularis oculi muscle

Question 14

What are the 3 limbs of the medial canthal tendon

Answer 14

Superior, anterior, posterior

Question 15

What limb of the medial canthal tendon covers the lacrimal fossa

Answer 15

superior

Question 16

What is Whitnall’s tubercle

Answer 16

insertion site of lateral canthal tendon

Question 17

Which part of lacrimal system is most vulnerable to injury

Answer 17

The inferior canaliculus near the medial canthal tendon

Question 18

In relation to the anterior lacrimal crest, where are the anterior and posterior ethmoid arteries and the optic canal

Answer 18

24-12-6 rule

Question 19

What does the medial epicanthal fold cover?

Answer 19

lacrimal lake

Question 20

What is the fnc of the deep head of the orbicularis oculi?

Answer 20

inserts on posterior lacrimal crest and provides structural support to lid

Question 21

what happens with disruption of deep head of orbicularis oculi

Answer 21

lateral and anterior displacement of the medial canthal angle

Question 22

where does the lateral canthal tendon insert

Answer 22

orbital tubercle located 5 mm posterior to the lateral orbital rim

Question 23

what is the fleshy pink mound of tissue in medial canthus

Answer 23

lacrimal caruncle

Question 24

what glands are contained w/in tarsal plates

Answer 24

tarsal glands (meibomian)

Question 25

which muscles are innervated by superior division of CN III

Answer 25

superior rectus and levator palpebrae superioris

Question 26

which muscles are innervated by inferior division of CN III

Answer 26

inferior oblique, inferior rectus, medial rectus

Question 27

What passes through superior orbital fissue

Answer 27

CN III, IV, VI, V1

Superior ophthalmic vein

Question 28

what is trichiasis

Answer 28

abnl direction of eyelashes

Question 29

what is gross asymmetry of eye mvmt

Answer 29

heterotropia

Question 30

What is an Argyll Robertson pupil

Answer 30

Accomodates but doesnt react (reacts to accomodation but not light) a/w syphilis