Conjunctiva + Orbicularis Oculi Flashcards
What is the difference between orbital and preseptal cellulitis?
Preseptal: anterior to orbital septum
Orbital: posterior to orbital septum
What raises/depresses the eyebrow?
Raised by frontalis muscle
Depressed by procerus, corragtor supercilii and orbicularis oculi
Innervated by facial nerve branches
What are the origins and insertion of the frontalis muscle?
Originates midway from epicranial aponeurosis and SOM
Inserts onto thick skin of the eyebrows not to bone
Describe the corrugator muscle
Lies beneath frontalis and orbicularis oculi Supratrochlear nerve passes through Supraorbital nerve passes under it Inserts onto underside of frontalis Pulls eyebrows medially and inferiorly
Describe the procerus muscle
Pulls forehead inferiorly-aging frown lines
Fat protrudes under each edge to assist movement
Extends vertically between the eyebrows
Merges with frontalis
What is the embryological origin of the eyelid?
ECTODERM (surface)-> skin
ECTODERM (inner layer) -> conjunctiva
Fusion of eyelids occurs at 9 weeks and the eyelids separate at 25 weeks
Describe the surface anatomy of the eyelid
30-32mm horizontal
8-11mm vertical
Laterally eyelid is contact with the globe
Medially eyelid is displaced from the globe
Point of maximum concavity: UL medial to pupil. LL lateral to pupil.
What is normal upper lid height and which muscles maintain this?
1-2mm below superior limbus
Maintained by balance between upper eyelid retractors+protractors (levator muscle, Muller’s muscle, frontalis muscle and orbicularis oculi)
What is the definition of the ptosis?
Marginal reflex distance of <2.5mm
Mild 2mm
Moderate 3mm
Severe 4mm
What are the gender differences in eyebrows?
Male: straight heavy low brow
Female: high arch brow, more defined eye crease
What is the eyelid margin?
Transition zone between skin and conjunctiva
Keratanised squamous epithelium-> non keratin SSE-> columnar epithelium of conjunctiva
Posterior margin applied to globe, anterior margin holds eyelashes
What is the grey line?
Junction between anterior and posterior lamellae
Meibomian glands open behind the grey line
What are the glands of the eyelids?
Sebaceous glands: Meibomian glands-not associated with follicles. 25 UL, 20LL
-> form chalazion when blocked
Apocrine glands
Eccrine glands (sweat)
Describe the eyelashes
3-4 layers UL
1-2 layers LL
Entropion can cause lash ptosis
What are the layers of the eyelid?
Anterior lamellae: skin, orbicularis oculi
Posterior lamellae: tarsal plate, conjunctiva
6 structural planes: Skin (very thin) Loose connective tissue (no fat) Orbicularis oculi (CN VII) Orbital septum (dense fibrous sheet) Tarsal plates/ meibomian glands Levator palpebrae superioris (superior lid only CN III) + Muller muscle (sympathetic) Palpebral conjunctiva
Describe the skin of the eyelid?
Epidermis: 3-4 cell layers thick Thinnest skin in body Attached loosely to orbicularis Firmly attached to canthal tendons No subcutaneous fat, ideal for skin grafts for reconstruction of lower eyelid
Describe the orbicularis oculi muscle
Closes lids
Flat sheet muscles encircling lids
Orbital
Preseptal + Pretarsal layers
Describe the attachments of the orbital part of the OO
Attached from supraorbital notch of frontal bone to near infraorbital foramen
Spreads onto forehead, covers corrugator, continues laterally over anterior temporalis fascia
Covers origins of elevator muscles of upper lip and the origin of the masseter
Describe where the preseptal and pretarsal muscles lie
Fixed medially and laterally and the canthal tendons
Circumnavigates around the eye
Preseptal: lies anterior to orbital septum + helps in lacrimal pump
Pretarsal: lies on tarsal plate
Describe the two heads of the pretarsal orbicularis
Superficial/ anteror: forms anterior limb of medial canthal tendon. Lies anterior to canaliculus and inserts onto maxillary bone
Deep/posterior: horner’s muscle. Inserts into lacrimal fascia and posterior lacrimal crest
What is at the medial canthus?
Lacrimal drainage apparatus
Medial canthal tendon
Rounded angle and hollowing
Describe the 3 limbs of the medial canthal tendon
Superior: inserts onto orbital process frontal bone. Provides vertical support and lacrimal pump mechanism
Anterior: inserts onto orbital process of maxilla anterior and above ALC, provides main support
Posterior: passes posteriorly between superior and inferior canaliculi, keeps lid apposed to the globe. May or may not exist
Describe the lateral canthal tendon
Y shaped fibrous thickening in the orbital septum runs from the end of the tarsal plates Whitnall’s tubercle
Describe the orbital septum
Originates at acrus marginalis at orbital rim
Divides eyelid into anterior and posterior
Keeps orbital fat posterior
Fuses with upper lid near superior tarsal border and capsulopalpebral fascia of the lower lid
Where does the orbital septum sit in terms of the lateral and medial canthal tendons
Sits in front of LCT
Passes in front of superior oblique trochlear pulley and runs backwards between OO and PL
Where does the orbital septum become thin and why?
Superomedially to allow passage of infratrochlear NVB and branches of superior ophthalmic vein
How do you identify the orbital septum during surgery?
Firm resistance to traction due to attachment to arcus marginalis
Do not ever suture
What are the tarsal plates?
Dense fibrous tissue providing structural integrity of the eyelids
25mm horizontally
1-1.5mm thick 3.5-4mm thick in lower lid
What is the function of the preaponeurotic fat pad in UL
Cushion to eyelid
Important surgical landmark as eyelid retractors are immediately posterior
UL : medial and centrl fat pads
LL: 3 fat pads, medial, central and temporal
IO separates medial from central fat pads
What is the superficial masculoaponeurotic system?
Fibromuscular layer connecting all muscles of facial expression
What are the orbital retaining ligaments?
Attach OO to orbital rim and beyond
Runs from periosteum to LO margin
Where does the lacrimal gland sit?
Superolateral orbit in lacrimal fossa Wrapped around posterior border lateral horn levator aponeurosis Anterior: orbital septum Posterior: orbital fat Inferior: IR laterally Palpebral part 1/3 size of orbital part
What are the upper lid retractors?
Levator muscle +Mullers muscle elevate eyelid
What is the origin and insertions of the levator palpebrae superioris?
Arises from lesser wing of sphenoid by short tendon
35-40mm long
Passes forward horizontally ends as aponeurosis vertically
Supplied by occulomotor nerve
What is Whitnall’s superior transverse ligament?
Thickens LPS
Inserts medially onto trochlea, bone and SON
Inserts laterally onto capsule of lacrimal gland and orbital wall
Part of circum-orbital fascial ring with Lockwoods ligament
Should not be severed during ptosis surgery
Contributes to suspensory ligament of superior fornix
Describe the levator aponeurosis
2 horns
30mm wide
Inserts into OO at level skin crease below anterior surface
Medial horn more tenuous than lateral- accounts for lateral shift of superior tarsus in the elderly- should not be severed
Lateral horn inserts onto zygomatic bone. Severed in surgery for thyroid eye disease but should not be damaged in ptosis surgery
Where does Muller’s muscle sit?
Arises under LPS
15-20mm wide
Descends between levator aponeurosis and conjunctiva to insert on upper border of the tarsal plate
Adherent to conjunctiva and very vascular
Supplied by sympathetic nerves
What retracts the lower lid?
Capsulopaplebral fascia and inferior tarsal muscle
Arise as a direct extension of the inferior rectus
What are the 3 components of the conjunctiva?
Palpebral (connected to posterior surface tarsus)
Forniceal (superior fornix is 10mm above limbus)
Bulbar
What is the blood supply to the eyelids?
Anterior lamellae: branches of external carotid (transverse facial, superficial temporal and angular arteries)
Posterior lamellae: arcades- superior medial palpebral artery and superior lateral palpebral artery (from lacrimal)
Multiple anastomoses between supratrochlear and supraorbital arteries, infraorbital and facial arteries
What does the lacrimal artery supply?
Lacrimal gland
Upper Eyelids
Forehead
Scalp
What is the venous drainage of the eyelids?
Veins are in fornices
Medial: Angular vein drains into superior orbital vein posteriorly and inferiorly into the facial vein
Lateral: superficial temporal artery and vein
Venous blood drains inferior ophthalmic vein
What is the lymphatic drainage of the eyelids?
Lateral 2/3 UL and later 1/3 LL to preauricular lymph nodes
Medial 1/3 UL and medial 2/3 LL to submandibular lymph nodes
What is the sensory nerve supply of the lids?
V1 and V2
Infratrochlear nerve= medial UL and LL
Infraorbital nerve=central LL
Lateral lid, temple= zygomaticofacial nerve
What is the motor supply of the eyelids?
Facial nerve
Runs from stylomastoid process to the mandible
Enters parotid and divides into 5
What are the 5 branches of the facial nerve?
Temporal Zygomatic Buccal Mandibular Cervical
What is Horner’s syndrome?
An interruption of the sympathetic pathway from the hypothalamus to the orbit
What are 3 orders of neurons involved in Horner’s syndrome?
1st order- posterolateral hypothalamus runs to lower cervical upper thoracic spinal cord
Preganglionic (2nd)-leave spinal cord, travel up apex lung around subclavian artery to the superior cervical ganglion at the angle of mandible
3rd- ascends along carotid sheath, may follow ophthalmic artery through cavernous sinus, travels along CNV through ciliary ganglion
What are the clinical features of Horner’s syndrome?
Ptosis Miosis Anisocoria Apparent enophthalmos Ipsilateral facial hyperemia
What is different about the asian eyelid?
Absent skin crease
Septum inserts lower on aponeurosis
How do the eyelids change over time?
Loss of collagen Atrophic dermis Atrophy of orbital fat Laxity of orbital septum Entropion and exotropion Brow ptosis Loss of lacrimal secretion
How does the lateral canthus differ from the medial canthus?
Lateral canthus 2mm higher than medial
What are the two potential spaces of the eyelid?
Pretarsal space- visible surgically
Preseptal space-not visible surgically as the orbicularis muscle is firmly adherent to the underlying septum
What are the boundaries of the pretarsal space?
Fusiform in shape Anterior: levator aponeurosis+OO Posterior: Tarsal plate +Mullers muscle Apex:Mullers muscle and levator muscles Lower edge: insertion of aponeurosis into tarsal plate
What are the borders of the preseptal space?
Triangular
Anterior: OO
Posterior: Septum and aponeurosis fibres piercing the OO muscle
What are the key differences between the upper and lower lids?
- size of tarsal plates
- # and rows of eyelashes
- direction of eyelashes
- development of retractor complex
- distribution of accessory lacrimal glands
- absence of LL peripheral arterial archade
- definition of skin crease
- number of fat pads
What separates the muscle of Riolan from the pretarsal orbicularis?
Glands of moll
Can be both superficial and deep to Meibomian glands
What is the Jones muscle?
The deep portion of the preseptal orbicularis oculi muscle
Where do vessels of the orbit run relative to the connective tissue?
Orbital arteries are not enclosed within connective tissue septa but are enclosed within
Veins are embedded within the septae
The superior ophthalmic vein lies in a connective tissue hammock
What smooth muscle is present in the orbit, superiorly, inferiorly, medially and laterally?
Superior: Muller’s muscle
Inferior: inferior palpebral muscle
Medial: scattered fibres in tenons capsule
Lateral: none
What is the most common muscular eye issue in the case of trauma to the orbit?
Deficient upgaze
