Chapter 30 - Orbital Surgery

Question 1

Most common cause of proptosis in adults

Answer 1

Thryoid eye disease

Is also most common extra-thyroid manifestation of graves disease

Question 2

7 bones of orbit

Answer 2

lesser wing sphenoid, frontal (roof), maxillary, palatine, zygomatic (floor), ethmoid, maxillary, lacrimal, sphenoid (medial wall), zygomatic, greater sphenoid (lateral)

Question 3

Orbit dimensions

Answer 3

30mL

Entrance height 35mm, width 40mm

Question 4

Optic foramen

Answer 4

through lesser wing of sphenoid from MCF to orbital apex

Contains CN II, ophthalmic a, SNS from carotid plexus

Question 5

Supraorbital foramen

Answer 5

medial third superior margin rim

Supraorbital n/a/v

Question 6

Anterior ethmoid foramen

Answer 6

frontoethmoidal suture
24mm posterior to rim
anterior ethmoid vessels/nerve

Question 7

Posterior ethmoidal foramen

Answer 7

12mm posterior to ant ethm foramen, jxn medial wall/roof

posterior ethmoid vessels/nerve

Question 8

24/12/16 rule

Answer 8

Anterior ethmoid artery (24mm)
Posterior ethmoid (12mm)
Optic nerve (6mm) in sequential measurements from posterior lacrimal crest

Question 9

Two foramen in lateral wall of orbit

Answer 9

Zygomaticotemporal/facial

Question 10

Nerves going through Sup and Inf portions of SOF

Answer 10

Sup: frontal, lacrimal br V1, IV

Inf: III, nasociliary V1, VI, SOV, SNS

División vía lateral rectus

Question 11

Nerves through IOF

Answer 11

V2 branches

IOV

Question 12

One EOM not originating at apex

Answer 12

Inferior oblique - originates from shallow depression in orbital plate of maxillary bone

Question 13

Blood supply to EOM

Answer 13

Ophthalmic, lacrimal, infraorbital

Question 14

Blood supply to eye

Answer 14

Ophthalmic branches (central retinal, lateral/medial posterior ciliary, lacrimal, muscular, supraorbital, A/P ethmoid, suprateochlear, nasofrontal, dorsonasal aa

Question 15

Orbital anastomoses between ECA, ICA

Answer 15

Lacrimal a, transverse facial/STA

Dorsonasal, angular

Question 16

Infraorbital a is branch of?

Answer 16

Maxillary a

Question 17

Describe venous drainage of orbit

Answer 17

IOV … pterygoid plexus…SOV…Cav Sinus

SOV originates sup/med, crosses midorbit below sup rectus, joined by lacrimal v

Question 18

Anatomy of lacrimal gland

Answer 18

8-13 ductules into fornix

Accessory lacrimal glands (for basal tearing) in eyelid…papillae medal posterior lid, lead to lacrimal sac

Question 19

Valve of rosenmuller

Answer 19

Medial end of common canaliculus (tract from accessory gland upp/low eyelid, prior to entering sac), to prevent tear reflux

Question 20

Advantages of endoscopic DCR

Answer 20

Preserve orbic pump mechanism
Better anatomy preservation (medial canthus)
Dec bleed

Question 21

Main Indication for DCR

Answer 21

Epiphora

Question 22

Causes of epiphora

Answer 22

NLDO

infxn, stone, tumors, other obstruction

Question 23

How to Dx NLDO

Answer 23

Dye disappearance test
Lacrimal irrigate/probe
Scintigraphy
Contrast dacryocystography

Question 24

Importance of maxillary line in DCR

Answer 24

Corresponds to suture between frontal process maxilla, lacrimal bone

Landmark for lacrimal sac, uncinate, superior attach middle turb

Question 25

How to do DCR

Answer 25

Sickle knife for mucosal flap over lacrimal sac Remove lacrimal bone and frontal process maxilla to expose medial lacrimal sac Incise and marsupialize sac into nasal cavity, silicone intubation stent

Question 26

Pathogenesis thyroid eye disease

Answer 26

TSH receptor autoantigen in eye Fibroblasts, adipocytes Cytokine-mediated immunologic Response Tissue inflammation, hypertrophy

Question 27

Sx of thyroid eye disease

Answer 27

Blurry, FB sensation, photophobia, tear, diplopia, dull pain, discomfort Eyelid retract (90%), periorbital ST swell, lid lag, lagophthalmos, conj inject, exposure keratopathy, restrictive myopathy, exophthalmos, optic neuropathy

Question 28

imaging findings graves opthalmopathy

Answer 28

Fusiform enlargement EOM | May see optic nerve compression (MRI)

Question 29

Conservative Tx TED

Answer 29

Self-limited 80% Ocular lubrication, cool compress, sunglasses Thyroid meds Steroids if active Rads, immumod

Question 30

Indications for surgery TED

Answer 30

Compressive optic neuropathy, exposure keratopathy, disfigure proptosis Diplopia common presentation Orbital Decom Stage 1 Then strabismus surgery Then eyelid

Question 31

Optic nerve anatomy and segments

Answer 31

Covered by dura Intraocular, orbital, canalicular, cranial Optic canal formed by lesser wing sphenoid, travels with ophthalmic a

Question 32

When to do surgery: indirect vs direct traumatic optic neuropathy

Answer 32

Indirect (neuropathy due to anything but the actual traumatic force), however medical management may suffice (systemic steroids), definitely consider surgery if incomplete vision loss and fail steroids Direct is from penetrating trauma injuring nerve

Question 33

How to access orbit for decompression

Answer 33

Intranasal | Transconj