Day 1 (1): Anatomy of the Orbit, Eyelid and Lacrimal System Flashcards
Borders of the bony orbit
Superior: Anterior cranial fossa
Medial: Nasal cavity and ethmoid air cells
Inferior: Maxillary sinus
Lateral: Middle cranial fossa and temporal fossa
7 Bones of the Bony Orbit
- Frontal bone
- Ethmoid bone
- Lacrimal bone
- Maxillary bone
- Zygomatic bone
- Sphenoid bone
- Palatine bone
Descriptors of the bony orbit
- Shape: Quadrilateral pyramid but spheroidal
- Base: Orbital margin
- Apex: Optic strut (between medial end of SOF and optic foramen)
- Orientation: anteriorly, laterally & inferiorly
- Widest part: 10-15 mm behind the anterior orbital rim (corresponds to equator of globe)
Dimensions of bony orbit
- Volume: 30 mL (constant unlike volume of orbital soft tissues)
- H x W of entrance: 35 mm x 40 mm
- Medial wall length: 45 mm
- Distance post. globe to optic foramen: 18 mm
- Length of orbital segment of ON: 30 mm
Hence, the S-shaped contour of the ON
Most common cause of unilateral or bilateral lid retraction and axial proptosis
Thyroid Eye Disease
Types of Thyroid Eye Disease
Type 1: fatty hyperplasia + tissue edema WITHOUT restrictive myopathy
Type 2: EOM enlargement WITH restrictive myopathy
- IR > MR > SR > LR [“Eye (I) Mo So Laki]
Anterior displacement of the eyeball due to increase in orbital content volume
Form of anterior decompression of the orbit
Proptosis
CT scan difference of proptosed vs unproptosed eye
NORMAL
1. Equator (widest part of the globe) should coincide with the widest part of the bony orbit behind the anterior orbital rim
2. ON with S-shaped contour
PROPTOSED
- Increase in orbital fat volume (Type I) OR
- Enlargement of extraocular muscles (Type 2)
1. Anterior displacement of globe
2. Equator is anterior to orbital rim/margin
3. Straightening of the ON
Remember:
Orbital volume remains constant at 30 mL
Roof of the orbit
rooFS
2 bones: Frontal + Lesser wing of Sphenoid
DEMARCATIONS:
Lateral:
Superior orbital fissure (separates Lesser wing from Greater wing)
Frontosphenoidal suture
Frontozygomatic suture
Medial:
Frontoethmoidal suture
Frontolacrimal suture
Frontomaxillary suture
Landmarks/Important Structures in the Roof of the Orbit
Lacrimal fossa: lacrimal gland
Trochlear fossa: trochlea of SO
Supraorbital notch: supraorbital vessels and nerve
Bones forming middle cranial fossa
Sphenoid bone (shaped like wings of a bat) and 2 temporal bones on either side
Boundaries of the SOF and IOF
SOF: between 2 wings of the sphenoid
IOF: between maxillary bone and greater wing of the sphenoid
Disease presenting with absence of orbital roof
Sphenoid bone dysplasia
- prolapse of contents of middle cranial fossa into orbit
Presentation of Neurofibromatosis Type 1 or Recklinghausen’s Disease?
- Sphenoid bone dysplasia: pulsating proptosis
- anterior and inferior displacement of globe due to prolapse of middle cranial fossa contents - Optic nerve glioma
- Plexiform neurofibroma/Fibroma molluscum
- Cafe-au-lait spots
- Axillary freckling
- Lisch nodules: 1 to 2 mm yellowish-brown dome-shaped solid lesions over the iris surface
- X-ray: remodelling and thickening of orbit due to chronicity
Thinnest wall of the orbit
Medial wall
Characteristics of medial wall
- Length: 45 mm
- Parallel to each other (25 mm apart) and to the sagittal plane
4 bones of the medial wall
SMEL
- Sphenoid bone (lesser wing)
- Maxillary bone (frontal process)
- Ethmoid bone (orbital plate)
- Lacrimal bone: THINNEST bone of orbit
Landmarks in the medial wall
Lacrimal Sac Fossa
Borders:
Anterior Lacrimal Crest: anterior border of LF; part of maxillary bone
Posterior Lacrimal Crest: posterior border of LF; part of lacrimal bone
Normal relationship of lacrimal sac fossa, ethmoid air cells and middle turbinate
N: LSF should be anterior to both tip of middle turbinate and ethmoid air cells
When entering the nasal cavity through the orbit, structures encountered:
1. Lacrimal bone
2. +/- Ethmoid air cells if anteriorly placed
3. Nasal cavity SUPERO-ANTERIOR to the middle turbinate
Shortest wall of the orbit
Floor of the orbit
- triangular in shape
3 Bones of the Orbital Floor
PaMaZa
- Palatine Bone
- Maxillary bone: THINNEST bone of the floor
- especially thin in the area MEDIAL to the infraorbital groove - Zygomatic bone
Landmarks in the Floor of the Orbit
- Infraorbital Groove
- in the middle of the posterior part of the orbital surface of the maxillary bone
- passage of infraorbital artery, vein and nerve which all exit the orbit through the Infraorbital Foramen - Nasolacrimal Groove
- houses nasolacrimal duct
Most common type of blow-out fracture
Orbital Floor Blow-out Fracture
- due to inherent thinness of the maxillary bone medial to the infraorbital groove
- d/t blunt trauma from a NON-PENETRATING object –> posterior compression of orbital contents towards apex –> sudden increase in intra-orbital pressure –> fracturing of the bone at the weakest point
- compressive forces at the orbital rim –> direct deformation of floor
Most common locations of orbital bone fractures
- Medial wall (lacrimal +/- ethmoid bone): thinnest wall
- Orbital floor medial to the infraorbital groove (maxillary bone)
- causes entrapment of orbital soft tissues or even IR prolapsing into maxillary sinus
Signs of orbital floor blow-out fracture
- Enophthalmos: posterior displacement of the eye (sunken eye)
- Diplopia: double vision due to impaired binocularity of the eyes
- Limitation on up-gaze (IO) and downgaze (IR)
- Infraorbital nerve dysfunction due to entrapment of infraorbital nerve in the groove
- Lid edema
- Lid emphysema: entry of air from maxillary sinus into orbit
Difference of Exophthalmos vs Proptosis
Exophthalmos: protrusion due to TED
Proptosis: protrusion due to other causes
Thickest wall of the orbit
Lateral wall
- triangular
- 45 degree angle with medial wall
Bones of lateral wall of orbit
Sa Zide
- Greater wing of Sphenoid bone
- Zygomatic bone
Landmarks of Lateral Wall of Orbit
- Frontozygomatic suture: between frontal bone and zygomatic bone
- Superior Orbital Fissure
- space between the two wings of the sphenoid
- boundary of lateral wall and roof
+ Greater wing: lateral wall
+ Lesser wing: roof - Inferior Orbital Fissure
- space between the maxillary bone and greater wing of sphenoid
- boundary of lateral wall and floor
+ Greater wing: lateral wall
+ Maxillary bone: floor
Surgical access into the orbit is most accessible through which route?
Lateral Orbitotomy
- through the lateral wall
What are the different apertures in the orbit?
Medial to Lateral:
- Nasolacrimal Canal: housing the NLD
- Ethmoidal Foramina (Anterior and Posterior)
- Optic Foramen: leading into optic canal
- Superior Orbital Fissure: between 2 wings of Sphenoid
- Inferior Orbital Fissure: between maxillary bone and greater wing of Sphenoid
- Zygomaticotemporal and Zygomaticofacial Canals
What passes through the ethmoidal foramina?
Ethmoidal artery, vein and nerves
Clinical correlate: Route of entry for infection and neoplasms from ethmoid sinuses and nasal cavity into the orbit
Most common cause of orbital cellulitis?
Ethmoid Sinusitis
- gaining entry into the orbit via the Ethmoidal Foramina
- with or without abscess formation
- cranial CT: hyperdensity of the ethmoid with hypodensity in the adjacent orbit signifying abscess formation
What are the 8 structures passing through the the Superior Orbital Fissure?
In between the greater wing (lateral wall) and lesser wing (roof) of Sphenoid bone
Contents: LFSTONOAS
Lateral part:
1. Lacrimal nerve (V1)
2. Frontal nerve (V1)
3. Superior Ophthalmic Vein
4. Trochlear nerve (IV)
Medial part: within the Annulus of Zinn
5. Oculomotor nerve - Superior division (III S)
6. Nasociliary nerve (V1)
7. Oculomotor nerve - Inferior division (III I)
8. Abducens nerve (VI)
9. Sympathetic nerve fibers
- proximally: travel with CN6
- distally: travel with CN5A as it enters SOF
Presentation of SOF fracture
- Ophthalmoplegia: paralysis of EOMs
- limitation of EOM movement due to neuropathy of CN III, IV and VI - Ptosis: drooping of upper lids (CN III to LPS)
- Proptosis: decreased EOM tension with loss of innervation +/- soft tissue edema
- Fixed pupil: CN III to iris sphincter (parasympathetic constrictor) and sympathetic fibers to iris dilator
- Lacrimal hyposecretion: lacrimal nerve to lacrimal gland (V1)
- Loss of corneal sensation: nasociliary nerve to cornea (V1)
What structures pass through the Inferior Orbital Fissure?
Between orbital floor and lateral wall (maxillary bone and greater wing of Sphenoid)
- Inferior Ophthalmic Vein
- Maxillary nerve (CN5B): continues as Infraorbital nerve after exit of branches
- Infraorbital artery and vein: travel in the infraorbital groove –> canal –> foramen
- Zygomatic nerve (CN5B):
- branch of the Maxillary nerve
- branches into the ZygomaticoTemporal + ZygomaticoFacial nerve - Parasympathetic fibers to lacrimal gland
- Collateral Meningeal Arteries
What structures pass through the ZygomaticoTemporal and ZygomaticoFacial foramen?
Branches of the Zygomatic nerve:
1. ZGT Foramen: ZygomaticoTemporal NAV
2. ZGF Foramen: ZygomaticoFacial NAV
What structure passes through the nasolacrimal canal?
Nasolacrimal Duct
- continuation of lacrimal sac located in the lacrimal sac fossa between the lacrimal and maxillary bone (frontal process)
- exits into the INFERIOR meatus under the INFERIOR turbinate
What structures are contained in the optic canal?
- 8 - 10 mm long canal terminating in the orbit via the optic foramen
- located in the LESSER wing of sphenoid bone
Optic Strut
- apex of the orbit
- part of the LESSER wing of the sphenoid bone that separates the SOF from the optic canal
Contents:
1. Optic Nerve
2. Ophthalmic Artery
Common presentation of Sphenoid Wing Fracture and Sphenoid Wing Meningioma?
Blurring of vision due to compression of CN II at the level of the optic canal
Sphenoid Wing Meningioma:
- arises from the arachnoid membrane
- 20% of intracranial meningiomas
- causes hyperostosis or bone thickening
Hyperostosis
- MC skull change associated with meningioma
- either due to the tumor stimulating osteoblastic activity in the adjacent bone or from periosteal stimulation via tumor invasion
- (+) prominent temple
6 Structures passing within the Annulus of Zinn?
Optic Canal
1. Optic Nerve (2)
2. Ophthalmic Artery
Superior Orbital Fissure
3. Oculomotor nerve - Superior Division (3S)
4. Nasociliary nerve (5A)
5. Oculomotor nerve - Inferior Division (3I)
6. Abducens nerve (6)
Primary arterial supply of the orbit?
Internal Carotid Artery:
Ophthalmic Artery:
- primary arterial supply of the orbit
External Carotid Artery:
1. Facial Artery: along the angle of the mandible
2. Maxillary Artery: terminal branch
3. Superficial Temporal Artery: terminal branch
What are the 9 branches of the Ophthalmic Artery?
DR MCLESSI
- Dorsal Nasal Artery
- (Central) Retinal Artery
- Muscular Artery
- Ciliary Arteries (Long Posterior, Short Posterior, Anterior)
- Lacrimal Artery
- Ethmoidal Arteries (Anterior and Posterior)
- Supraorbital Artery
- Supratrochlear Artery (Frontal Artery)
- Internal Palpebral Artery (Lateral and Medial)
Ocular group: vessels to the globe and EOMs
CAMP
1. Central retinal artery
2. Posterior ciliary arteries (Long and Short)
3. Anterior ciliary artery
4. Muscular arteries (Superior and Inferior)
Orbital group: vessels to the orbit
SSLIDE
1. Lacrimal artery
2. Supraorbital artery
3. Supratrochlear artery/Frontal artery
4. Ethmoidal artery (Anterior and Posterior)
5. Internal palpebral artery (Medial and Lateral)
6. Dorsal nasal artery
Describe the branching of the Ophthalmic Artery
- Central Retinal Artery: first and most important branch of the OA
- end artery and no collateral circulation
- branches off before OA crosses over the ON
Lateral Branch
- Ciliary Artery
- Lacrimal Artery
- (Lateral) Internal Palpebral Artery
Medial Branch
- Muscular Artery
+ Ciliary Artery - Supraorbital Artery
- Anterior and Posterior Ethmoidal Artery
+ (Medial) Internal Palpebral Artery - Supratrochlear Artery
- Dorsal Nasal Artery
What structures are supplied by the branches of the OA?
- Central Retinal Artery
- ONH & ant. 2/3 of retina (NFL, GCL, IPL, INL) - Ciliary Arteries:
- Short Posterior CA: posterior choroid, posterior 1/3 of retina (OPL, ONL, PRL, RPE) and ONH (via the Circle of Zinn-Haller)
- Long Posterior CA and Anterior CA: anterior segment, ciliary body and anterior choroid - Lacrimal Artery: lacrimal gland
- Internal Palpebral Artery: upper and lower eyelid
- Muscular Artery: EOMs
- Supraorbital Artery: SR, LPS, skin, muscles and periosteum of forehead
- Ethmoidal Artery: ethmoidal air cells, lateral wall of nasal cavity, nasal septum
- Supratrochlear Artery: skin, muscles and periosteum of forehead
- Dorsal Nasal Artery: lacrimal sac, NLD, dorsum of nose
Central Retinal Artery Occlusion (CRAO)
- Ophthalmic emergency
- Causes: ICA/OA/CRA atherosclerosis, embolism, vasculitis
- Sequelae: rapid ischemia and infarction of ON and inner retina
- Presentation: ACUTE, UNILATERAL, PAINLESS VISION LOSS
What does the branches of the ECA supply in relation to the orbit?
- Facial Artery –> Angular Artery: lacrimal sac and NLD (with Dorsal Nasal Artery)
- Maxillary Artery –> IOF –> Infraorbital Artery: IR, IO, lacrimal sac (with Dorsal Nasal Artery to lacrimal sac and Muscular Artery to EOMs)
- Superficial Temporal Artery –> Zygomatico-Orbital Artery –>
- ZygomaticoTemporal Artery: pass through ZGT foramen
- ZygomaticoFacial Artery: pass through ZGF foramen
- orbicularis oculi
- anastomosis with Lateral Internal Palpebral Artery and Lacrimal Artery (from the OA <— ICA)
Discuss blood supply of eyelids
- Derived from both facial system (from ECA) and orbital system (from OA and ICA) with multiple anastomosis and collateral circulation
- includes ff. arteries:
1. Supratrochlear A. –> Frontal A.
2. Supraorbital A.
3. Lacrimal A.
4. ZygomaticoFacial & ZygomaticoTemporal A.
5. Infraorbital A.
6. Facial A. –> Angular A.
7. Dorsal Nasal A.
8. Medial and Lateral Internal Palpebral A. - Thus, even with complete occlusion of the OA, there may be no eyelid s/sx due to collateral circulation
Marginal Arcade
- 3 mm from free border of eyelid, just above ciliary follicles
- either between tarsal plate and OO or within tarsus
Peripheral Arcade
- along upper margin of tarsal plate, between the Muller muscle and the Levator Aponeurosis
GENERALIZED, GRANULOMATOUS inflammation of the blood vessels?
Temporal Arteritis/Giant Cell Arteritis/Horton’s Arteritis
Involves:
1. Superficial Temporal Artery (from ECA)
- (+) pain and tenderness in the scalp of temple
- Posterior Ciliary Arteries (from OA) to ON
- (+) sudden diplopia
- (+) U or B vision loss from Arteritic Anterior Ischemic Optic Neuropathy (AAION)
Dx:
Arterial Biopsy
- multi-nucleated giant cells in the vessel walls
Venous drainage of orbit
- veins with same name run along the arteries
- Superior Ophthalmic Vein: exits via SOF –> Cavernous Sinus
- MAJOR venous drainage - Inferior Ophthalmic Vein: exits via the IOF –> Pterygoid Plexus –> Maxillary Vein –> IJV
- MINOR venous drainage
Venous drainage of the eyelids
- veins with same name run along the arteries
- venous circulation of the eyelids via the SOV connect the Facial Vein and the Cavernous Sinus forming a route for spread of infection and thrombosis
- SUPERFICIAL or PRE-tarsal System
- Facial vein –> Internal Jugular Vein
- also drains the Danger Triangle of Face - DEEP or POST-tarsal System
- Superior Ophthalmic Vein –> Cavernous Sinus
What is the Cavernous Sinus?
- one of the dural venous sinuses creating a cavity called the Lateral Sellar Compartment
- located on both sides of the sphenoid bone and pituitary gland
- the only anatomic location in the body where an artery completely travels through and within a venous structure
- convergence site of the cranial nerves, ICA, pituitary gland and sphenoid sinus
Borders:
Roof: Optic nerve, chiasm and tract, ICA
Floor: Foramen lacerum, junction of sphenoid body and greater wing
Medial: Pituitary gland (in the sella turcica), Sphenoid sinus
Lateral: Temporal lobe
Anterior: Orbital apex
Posterior: Petrous temporal bone
Contents:
1. Medial wall
- Abducens nerve (CN6)
- Internal Carotid Artery
2. Lateral wall: superior –> inferior (OTOM)
- Oculomotor nerve (CN3)
- Trochlear nerve (CN4)
- Ophthalmic nerve (CN5A)
- Maxillary nerve (CN5B)
3. Sympathetic nerve fibers
- proximally: travel with CN6
- distally: travel with CN5A as it enters SOF
Note:
- ALL nerves (including CN5A) enter the orbital apex via the SOF except the Maxillary nerve (CN5B) which exits via the FORAMEN ROTUNDUM
- Mandibular nerve (CN5C) does NOT enter the cavernous sinus; will exit cranium via the FORAMEN OVALE
What is the Sella Turcica?
- saddle-shaped depression in the body of the sphenoid bone
- located postero-medial to the two orbits
Hypophyseal Fossa
- most inferior aspect
- contains the pituitary gland
Most common cause of Carotid-Cavernous Fistula?
TRAUMA
- abnormal connection between the cavernous segment of the ICA with the cavernous sinus
- blood is shunted from the high-flow ICA into the low-flow CS without an intervening capillary bed
- capillary bed is important to dissipate the pressure due to its high surface area
- increase in venous pressure in the CS causes impaired venous drainage of the orbit
- presentation:
1) congestion due to impaired drainage
2) ischemia due to shunting of blood
3) mass effect due to congestion and edema - CT scan:
1) proptosis
2) enlarged SOV
Primary sensory nerves of orbit?
- Optic nerve (II): vision
- Trigeminal nerve (V): sensory innervation of eyes, conjunctiva, cornea, lacrimal gland and nasal mucosa
Primary motor nerves of orbit?
- Oculomotor nerve (III): LPS, SR, IR, MR, IO
- Trochlear nerve (IV): SO
- Abducens nerve (VI): LR
- Facial nerve: orbicularis oculi, muscles of facial expression
Remember: SO4LR6
Branches of the Trigeminal nerve pertinent to the orbit?
- Ophthalmic Division (V1)
- enters orbit via SOF
- Lacrimal nerve
- Frontal nerve
- Nasociliary nerve - Maxillary Division (V2)
- exits via Foramen Rotundum then enters orbit via the IOF
- Infraorbital nerve: continuation of V2
- Zygomatic nerve: branch
Nerves of the Ophthalmic Division of CN V (V1)
A. Lacrimal n: lacrimal GLAND, LATERAL upper lid and conjunctiva
B. Frontal n: 2 branches
1. Supraorbital n: CENTRAL upper lid and conjunctiva
2. Supratrochlear n: MEDIAL upper lid and conjunctiva
C. Nasociliary: 5 branches
1. Ciliary ganglion: gives off the Short ciliary n.
2. Long ciliary n: cornea, iris, ciliary body and sympathetic fibers to the iris dilator
3. Anterior ethmoidal n: anterior ethmoidal sinus
4. Posterior ethmoidal n: posterior ethmoidal sinus + sphenoid sinus
5. Infratrochlear n: MEDIAL upper lid and conjunctiva, lacrimal SAC
Nerves of the Maxillary Division of CN V (V2)
A. Infraorbital n: LOWER lid and conjunctiva
B. Zygomatic n: 2 branches
1. ZygomaticoTemporal n: lateral temple
2. ZygomaticoFacial n: lateral lower lid & cheek
Sensory presentation of orbital floor blow-out fracture?
Numbness over lower lid and cheek area
Due to entrapment and compression of the Infraorbital nerve and Zygomatic nerves
Function of the Facial nerve (CN VII)
Innervates the following:
1. Orbicularis Oculi:
- closes the eyes and brings lids together
- Muscles of facial expression
- Frontalis
- Procerus
- Corrugator supercilii
Palsy:
- eyelid laxity
- lagophthalmos: inability to close eyelids
- exposure keratitis
- drooping or inability to move facial muscles
What are the 7 extraocular muscles?
- Levator Palpebrae Superioris
- first muscle you see after removal of orbital plate of frontal bone - Superior Rectus
- Inferior Rectus
- Medial Rectus
- Lateral Rectus
- Superior Oblique
- Inferior Oblique
What are the innervation of the EOMs?
LPS, SR: Oculomotor n. (Superior division)
MR, IR, IO: Oculomotor n. (Inferior division)
SO: Trochlear n.
LR: Abducens n.
Where do the EOMs originate?
LPS
- Lesser wing of Sphenoid bone ABOVE the Annulus of Zinn
SR, IR, LR, MR
- Annulus of Zinn
SO
- Lesser wing of Sphenoid bone MEDIAL to the Annulus of Zinn and optic foramen
IO
- depression on the medial aspect of the Maxillary bone near the orbital rim
Where do the EOMs insert in the globe?
Recti muscles: Spiral of Tillaux
- attached anterior to equator
- distance from the corneal limbus: MILS
+ MR: 5.5 mm
+ IR: 6.5 mm
+ LR: 6.9 mm
+ SR: 7.7 mm
Remember: long axis of orbit is NOT THE SAME as the long axis of the globe; the EOMs lie along the long axis of the orbit
LPS:
- terminates as the levator aponeurosis and inserts into the:
1. trochlea
2. supraorbital notch
3. superior tarsus
4. lateral orbital tubercle
5. posterior lacrimal crest
SO:
- through the trochlea then under the SR and attach posterior to equator
IO:
- posterior inferotemporal quadrant at the level of the macula
What are the blood supply of the EOMs?
SR, SO, LPS:
- Lateral (Superior) Muscular Artery
IR and IO:
- Medial (Inferior) Muscular Artery
- Infraorbital Artery
MR:
- Medial (Inferior) Muscular Artery
LR:
- Lateral (Superior) Muscular Artery
- Lacrimal Artery
What are the basic movements of the EOMs?
Elevation: UPWARD movement along the vertical axis
Depression: DOWNWARD movement along the vertical axis
Adduction: MEDIAL movement (towards midline) along the horizontal axis
Abduction: LATERAL movement (away from midline) along the horizontal axis
Intorsion/Internal Rotation: rotation of the 12-hour clock position TOWARDS THE MIDLINE along the Z-axis (through the pupil)
Extorsion/External Rotation: rotation of the 12-hour clock position AWAY FROM THE MIDLINE along the Z-axis
What does the primary, secondary and tertiary actions of EOMs mean?
Primary: main and most powerful action
Secondary: second most powerful action
Tertiary: least powerful action
Action of the MR?
1: Adduction
Action of the LR?
1: Abduction
Action of the LPS?
1: Upper eyelid elevation
Action of the SR?
1: Elevation
2: Internal Rotation/Intorsion
3: Adduction
Action of the IR?
1: Depression
2: External Rotation/Extorsion
3: Adduction
Action of the SO?
1: Internal Rotation/Intorsion
2: Depression
3: Abduction
Action of the IO?
1: External Rotation/Extorsion
2: Elevation
3: Abduction
What are the adductors of the eye?
Medial Rectus - primary
Superior Rectus
Inferior Rectus
What are the abductors of the eye?
Lateral Rectus - primary
Superior Oblique
Inferior Oblique
What are the elevators of the eye?
Superior Rectus - primary when abducted; INTERNAL ROTATOR when adducted
Inferior Oblique - primary when adducted; EXTERNAL ROTATOR when abducted
What are the depressors of the eye?
Inferior Rectus - primary when abducted; EXTERNAL ROTATOR when adducted
Superior Oblique - primary when adducted; INTERNAL ROTATOR when abducted
What are the internal rotators of the eye?
Superior Oblique - primary when in primary gaze/abducted; DEPRESSOR
Superior Rectus - primary when adducted; ELEVATOR
What are the external rotators of the eye?
Inferior Oblique - primary in primary gaze/abducted; ELEVATOR
Inferior Rectus - primary when adducted; DEPRESSOR
Notes on EOM actions:
Recti: adductors (anteriorly inserted)
Obliques: abductors (posteriorly inserted)
Superiors = intortion
Inferiors = extortion
Remember:
INFERIOR people EXTORT
OBLIQUES move eye OUT
Layers of the eyelid?
A. ANTERIOR LAMELLA
1. Skin
2. Orbicularis Oculi
B. ORBITAL SEPTUM
C. POSTERIOR LAMELLA
1. Preaponeurotic Fat Pads
2. LPS (Levator Aponeurosis)/Inferior Retractors
3. Muller’s muscle (superiorly)
4. Tarsus (inferiorly)
5. Conjunctiva
Cutaneous landmarks in and around the orbit
- Upper lid crease: levator aponeurosis
- Lower lid crease: inferior retractors
- Infraorbital hollow: inferior border of lower lid
- Tear Trough + Nasojugal Fold: medial border
- Palpebromalar Fold: lateral border
Locations of elective skin incisions for better cosmetic results
- Transcoronal
- Pretrichial
- Mid-forehead
- Suprabrow
- Infrabrow
- Upper Lid Crease
- Lower Lid Crease
- Infraciliary: lateral to lateral canthus
- Nasojugal Fold
Wrinkles
- natural creases of the face
- perpendicular to underlying muscle
- elective surgical incisions should be placed along these creases for better cosmesis
Fibrous layer that contains the facial muscles
Superficial Musculo-Aponeurotic System (SMAS)
The safe avascular plane for tissue dissection in the face is between what layers?
Between deep galea aponeurotica and periosteum
SMAS of the orbit?
Orbicularis Oculi
SMAS of the scalp?
Galea Aponeurotica:
- splits into two superior to the frontalis muscle
A. Superficial GA:
- anterior sheath of frontalis and OO
B. Deep GA:
- posterior sheath of frontalis and OO
- apposed to the periosteum
- ensheaths the Brow Fat Pads (–> Preseptal Fat Pad inferiorly)
- splits at level of eyebrows into:
1. Anterior Deep GA
2. Posterior Deep GA
OIANA of the Orbicularis Oculi
Origin: Orbital Rim
Insertion:
- medial: Anterior and Posterior Lacrimal Crest
- lateral: Whitnall’s/Lateral Orbital Tubercle
- central: Eyelid skin
Action: Closes the eyelids
Innervation: Facial Nerve
Supply:
- Supraorbital A.
- Supratrochlear A.
- Zygomatico-Orbital A.
- Lacrimal A.
- Infraorbital A.
- Internal Palpebral A.
Parts of the Orbicularis Oculi
- Each portion has a SUPERFICIAL and DEEP head MEDIALLY
- SUPERFICIAL heads attach to ANTERIOR Lacrimal Crest
- DEEP heads attach to POSTERIOR Lacrimal Crest
- Lacrimal Sac: sandwiched between the superficial and deep heads of the palpebral OO
Parts:
A. Orbital OO - adjacent to the orbital rim
B. Palpebral OO
- PreSEPTAL: anterior to orbital septum
- Jones’ Muscle: medial DEEP head - PreTARSAL: anterior to tarsus
- Horner’s Muscle: medial DEEP head
- Riolan’s Muscle/Pars Ciliaris: marginal portion adjacent to eyelid margin
Superficial portion of Riolan’s Muscle is seen along the eyelid margin as a colored line called?
Gray Line
Thickening of the periosteum at the orbital rim
Arcus marginalis
What structures form the medial and lateral retinaculum?
Retinaculum
- fibrous bands of fascia around tendons that keep them in place
MEDIAL Retinaculum
1. Deep Head of PreTARSAL OO (Horner’s Muscle)
2. Medial Canthal Tendon
3. Orbital Septum
4. Medial Horn of Levator Aponeurosis (superiorly)
5. Whitnall’s Ligament (superiorly)
6. Lockwood/Suspensory Ligament (inferiorly)
7. Check Ligaments of the MR
LATERAL Retinaculum
1. Lateral Canthal Tendon
2. Orbital Septum
3. Lateral Horn of Levator Aponeurosis (superiorly)
4. Whitnall’s Ligament (superiorly)
5. Lockwood/Suspensory Ligament (inferiorly)
6. Check Ligaments of the LR
What is the Lockwood/Suspensory Ligament?
- Fusion of the capsulopalpebral fascia anterior to the IO
- Forms a support hammock below the globe extending from the lateral orbital tubercle to the medial canthal tendon
- Prevents inferior displacement of the globe
- Origin of the inferior tarsal muscle
What is the capsulopalpebral fascia?
- Lower eyelid retractor
- Extends anteriorly from the IR muscle sheath, splitting around the IO, fusing with the inferior orbital septum and inserting into the inferior border of the inferior tarsal plate.
What is the fibrous sheath beneath the OO?
Orbital Septum
Origin: Arcus marginalis
Insertion:
- Lateral: Whitnall’s Tubercle
- Medial: Posterior Lacrimal Crest
- Inferior: Levator aponeurosis (upper lid), Capsulopalpebral fascia or inferior border of inferior tarsal plate (lower lid)
Describe the 5 orbital fat pads.
Beneath the orbital septum
Upper lid (2):
1. Nasal fat pad
2. Preaponeurotic fat pad
Lower lid (3):
3. Nasal fat pad
4. Central fat pad
5. Temporal fat pad
Describe the Levator muscle and its aponeurosis.
Origin: Lesser wing of Sphenoid above the Annulus of Zinn
Length: 40 mm
Aponeurosis: tendinous portion anterior to the Whitnall’s Ligament
Insertion: fuses with Orbital Septum to insert into the skin (forming upper eyelid crease) and ANTERIOR surface of superior tarsal plate
Function: elevates the upper eyelid
Innervation: CN 3 (Oculomotor nerve - Superior Division)
Supply: Supraorbital Artery
Differentiate the superior tarsus from the inferior tarsus.
Superior Tarsus
- larger
- semilunar
- 10 mm in height
- anterior surface: Levator Aponeurosis
- superior margin: Superior Tarsal Muscle
Inferior Tarsus
- smaller and thinner
- elliptical
- 5 mm in height
- inferior margin: Inferior Tarsal Muscle and Capsulopalpebral Fascia
Drooping of the upper eyelid
Blepharoptosis
Analogous structures of the upper and lower lids
Levator Muscle :: Capsulopalpebral Head
Levator Aponeurosis :: Capsulopalpebral Fascia
Whitnall’s Ligament :: Suspensory Ligament
Muller’s Muscle :: Inferior Tarsal Muscle
What is the Whitnall’s Ligament?
Condensed fascia of the levator muscle 14-20 mm above superior border of superior tarsal plate
Attachments:
- medial: trochlear fascia and medial canthal tendon
- lateral: lacrimal gland capsule and Whitnall’s tubercle
Function: acts like a pulley that converts A-P pulling force of the LPS to a S-I direction to elevate the upper eyelids
Differences of Asian vs Caucasian eyes
Asians:
- Eyelid skin thicker
- Tarsal plates are smaller
- Preseptal and preaponeurotic fat pads extend more inferiorly down to superior tarsal border
- Levator aponeurosis insertion onto skin at the upper lid crease is less developed (monolid appearance)
- Levator aponeurosis and septum fuse below the tarsal border
What are the retractors of the lower lid?
- Capsulopalpebral Head
- formed by IR muscle sheath
- continues anteriorly to wrap around the IO - Lockwood/Suspensory Ligament
- condensation of the CPH anterior to the IO - Inferior Tarsal Muscle
- part of the CPF running from the Lockwood ligament to the inferior border of the tarsal plate - Capsulopalpebral Fascia
- fibrous expansion of the CPH and Suspensory Ligament anteriorly
- fuses with septum at or inferior to tarsal border
- attachments: skin, orbicularis oculi, inferior tarsal border, Tenon’s capsule and conjunctiva (as the Inferior Suspensory Ligament of the fornix)
Describe the lateral and medial canthal tendon.
Lateral Canthal Tendon
- Superior and Inferior crus join to form the Common tendon and attaches to the Lateral Orbital Tubercle/Whitnall’s Tubercle
Medial Canthal Tendon
- Formed by the preseptal and pretarsal OO
- Superior and Inferior crus join to form the Common tendon which then splits into the Anterior and Posterior limbs
- ANTERIOR limb: stronger; anterior to lacrimal sac; attaches to anterior lacrimal crest
- POSTERIOR limb: smaller; posterior to lacrimal sac and attaches to the posterior lacrimal crest; apposition of medial lid to globe
- SUPERIOR limb: debated; attaches to the frontal bone
What is the function and the parts of the lacrimal secretory apparatus?
Production of AQUEOUS portion of tears
Accessory Lacrimal Glands:
- BASAL tear production
1. Gland of Krause: conjunctival fornix
2. Gland of Wolfring: orbital border of tarsus
Lacrimal Gland
- REFLEX tear production
- exocrine gland similar to mammary and salivary gland
What are the parts of the lacrimal drainage system?
- Superior and Inferior Puncta
- Superior and Inferior Canaliculus
- Common Canaliculus
- Valve of Rosenmuller
- Lacrimal Sac
- Nasolacrimal Duct
- Valve of Hasner
What are the parts of the canaliculus?
Superior and Inferior Canaliculus (10 mm)
1st part: vertical; 2 mm
2nd part: horizontal; 8 mm
Common Canaliculus
- superior + inferior canaliculus
- seen in 90% of the population
What are the parts of the Lacrimal Sac?
- 15 - 20 mm
- Fundus: above Valve of Rosenmuller; 5 mm
- Body: below Valve of Rosenmuller; 10 mm
- Rests on the lacrimal fossa (maxillary and lacrimal bone) in between the anterior and posterior limbs of the MCT
How does the lacrimal pump work?
Pump: OO muscles (preseptal and pretarsal portion)
- when the eyelids are open and the OO relaxed, tears enter the puncta and canaliculi by capillary action and movement from an area of positive pressure (tear lake) to area with negative pressure (canaliculi).
- when eyelids close and OO contract, canaliculi traversing the OO is compressed increasing the pressure and forcing the tears into the lacrimal sac.
- when eyelids open again and OO relax, tears drain to NLD due to gravity and movement of fluid from area with positive pressure (lacrimal sac) to area with negative pressure.
What are the lacrimal valves and their function?
- Folds of mucosa that promote unidirectional flow and prevents backflow of tears
- Valve of Rosenmuller
- only true valve
- common canaliculus to lacrimal sac - Valve of Krause
- lacrimal sac to nasolacrimal duct
- NLD begins at this level - Valve of Hyrtl and Taillefer
- Valve of Hasner/Plica Lacrimalis
- NLD to inferior meatus
Describe the nasolacrimal duct.
- Continuation of the lacrimal sac at the level of the Valve of Krause
- Exits into the inferior meatus via the Valve of Hasner
- 2 parts: 17-20 mm
1. Intraosseous portion: within NL canal; 12 mm
2. Meatal portion: within inferior meatus; 5 mm
What are the common causes of tearing?
- Lacrimation: overproduction of tears
- Epiphora: obstruction of the drainage
How does Nasolacrimal Duct Obstruction (NLDO) present?
- Fullness at the medial canthal area due to dilation of the lacrimal sac
- Redness if inflamed/infected
- Regurgitation of fluid in the puncta after application of pressure over the lacrimal sac
What is Dacryocystorhinostomy?
Establishing a new communication between the mucosa of the lacrimal sac to the nasal cavity (level of the MIDDLE MEATUS) above the site of blockage to facilitate drainage of tears
OIANS of the Muller’s Muscle/Superior Tarsal Muscle?
Origin: Underside of LPS
Insertion: Superior border of superior tarsal plate
Action: Raises/maintains elevation of upper eyelid
Innervation: Sympathetic nervous system
Supply: Ophthalmic Artery via Supraorbital Artery
