Chapter 30 - Orbital Surgery Flashcards
Most common cause of proptosis in adults
Thryoid eye disease
Is also most common extra-thyroid manifestation of graves disease
7 bones of orbit
lesser wing sphenoid, frontal (roof), maxillary, palatine, zygomatic (floor), ethmoid, maxillary, lacrimal, sphenoid (medial wall), zygomatic, greater sphenoid (lateral)
Orbit dimensions
30mL
Entrance height 35mm, width 40mm
Optic foramen
through lesser wing of sphenoid from MCF to orbital apex
Contains CN II, ophthalmic a, SNS from carotid plexus
Supraorbital foramen
medial third superior margin rim
Supraorbital n/a/v
Anterior ethmoid foramen
frontoethmoidal suture
24mm posterior to rim
anterior ethmoid vessels/nerve
Posterior ethmoidal foramen
12mm posterior to ant ethm foramen, jxn medial wall/roof
posterior ethmoid vessels/nerve
24/12/16 rule
Anterior ethmoid artery (24mm) Posterior ethmoid (12mm) Optic nerve (6mm) in sequential measurements from posterior lacrimal crest
Two foramen in lateral wall of orbit
Zygomaticotemporal/facial
Nerves going through Sup and Inf portions of SOF
Sup: frontal, lacrimal br V1, IV
Inf: III, nasociliary V1, VI, SOV, SNS
División vía lateral rectus
Nerves through IOF
V2 branches
IOV
One EOM not originating at apex
Inferior oblique - originates from shallow depression in orbital plate of maxillary bone
Blood supply to EOM
Ophthalmic, lacrimal, infraorbital
Blood supply to eye
Ophthalmic branches (central retinal, lateral/medial posterior ciliary, lacrimal, muscular, supraorbital, A/P ethmoid, suprateochlear, nasofrontal, dorsonasal aa
Orbital anastomoses between ECA, ICA
Lacrimal a, transverse facial/STA
Dorsonasal, angular
Infraorbital a is branch of?
Maxillary a
Describe venous drainage of orbit
IOV … pterygoid plexus…SOV…Cav Sinus
SOV originates sup/med, crosses midorbit below sup rectus, joined by lacrimal v
Anatomy of lacrimal gland
8-13 ductules into fornix
Accessory lacrimal glands (for basal tearing) in eyelid…papillae medal posterior lid, lead to lacrimal sac
Valve of rosenmuller
Medial end of common canaliculus (tract from accessory gland upp/low eyelid, prior to entering sac), to prevent tear reflux
Advantages of endoscopic DCR
Preserve orbic pump mechanism
Better anatomy preservation (medial canthus)
Dec bleed
Main Indication for DCR
Epiphora
Causes of epiphora
NLDO
infxn, stone, tumors, other obstruction
How to Dx NLDO
Dye disappearance test
Lacrimal irrigate/probe
Scintigraphy
Contrast dacryocystography
Importance of maxillary line in DCR
Corresponds to suture between frontal process maxilla, lacrimal bone
Landmark for lacrimal sac, uncinate, superior attach middle turb
How to do DCR
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
Pathogenesis thyroid eye disease
TSH receptor autoantigen in eye
Fibroblasts, adipocytes
Cytokine-mediated immunologic Response
Tissue inflammation, hypertrophy
Sx of thyroid eye disease
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
imaging findings graves opthalmopathy
Fusiform enlargement EOM
May see optic nerve compression (MRI)
Conservative Tx TED
Self-limited 80%
Ocular lubrication, cool compress, sunglasses
Thyroid meds
Steroids if active
Rads, immumod
Indications for surgery TED
Compressive optic neuropathy, exposure keratopathy, disfigure proptosis
Diplopia common presentation
Orbital Decom Stage 1
Then strabismus surgery
Then eyelid
Optic nerve anatomy and segments
Covered by dura
Intraocular, orbital, canalicular, cranial
Optic canal formed by lesser wing sphenoid, travels with ophthalmic a
When to do surgery: indirect vs direct traumatic optic neuropathy
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
How to access orbit for decompression
Intranasal
Transconj
