Orthoptics 1 - Orbit and Extraocular Muscles

What bones form the roof of the orbit?1

Frontal bone and lesser wing of sphenoid

What bones form the floor of the orbit?1

zygomatic, maxilla and palatine

What bones form the lateral wall of the orbit?

zygomatic and greater wing of sphenoid

What bones form the medial wall of the orbit?

maxilla, lacrimal, ethmoid, sphenoid

What are the three main pathways into the orbit?

optic canal, superior orbital fissure and orbital apex

What is contained within the optic canal?

optic nerve (CN II) and ophthalmic artery

What is contained within the superior orbital fissure?

oculomotor nerve (CN III)
trochlear nerve (CN VI)
trigeminal nerve division 1 (CN V1): lacrimal, frontal and nasociliary nerve)
abducens nerve (CN VI)
superior ophthalmic vein

What is contained within the orbital apex?

zygomatic nerve (maxillary branch of trigeminal nerve)
infraorbital nerve (also from maxillary branch)
inferior ophthalmic vein

What is the primary blood supply to the orbit? Where does it come from?

Ophthalmic artery which comes from the internal carotid artery

DR MCLESSI (branches of ophthalmic artery)

D - dorsal nasal artery
R - (central) retinal artery
M - muscular branches --> anterior ciliary
C - (posterior) ciliary arteries (long and short)
L - lacrimal artery
E - ethmoid artery (anterior and posterior)
S - supraorbital artery
S - supratrochlear artery
I - internal/medial palpebral artery

What is the superior ophthalmic vein made up of?

superior vortex veins

What makes up the inferior ophthalmic vein?

inferior vortex veins

Where do the superior and inferior ophthalmic veins drain?

Into the cavernous sinus

Which of the ciliary veins is anterior and which is posterior?

LONG = anterior
SHORT = posterior

Name the 6 extraocular muscles

superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique

How far, in mm, is the superior rectus from the edge of the cornea?

7.7 mm

How far, in mm, is the medical rectus from the edge of the cornea?

5.5 mm

How far, in mm, is the inferior rectus from the edge of the cornea?

6.5 mm

How far, in mm, is the lateral rectus from the edge of the cornea?

6.9 mm

Where do all recti muscles originate?

common tendinous ring

Describe the common tendinous ring

a fibrous ring of connective tissue posterior to the orbital apex

Describe the superior rectus

Origin: superior part of the common tendinous ring
Insertion: anterosuperior sclera
Primary action: elevation
Secondary action: intorsion and adduction
Innveration: oculomotor nerve

Describe the inferior rectus

Origin: inferior common tendinous ring
Insertion: anteroinferior sclera
Primary action: depression
Secondary action: extorsion and abduction
Innveration: oculomotor nerve

Describe the medial rectus

Origin: medial common tendinous ring
Insertion: anteromedial sclera
Primary action: adduction
Innveration: oculomotor nerve

Describe the lateral rectus

Origin: lateral common tendinous ring
Insertion: anterolateral sclera
Primary action: abduction
Innervation: abducens nerve

Describe the main differences between the recti and oblique muscles

the recti muscles run straight from origin to globe whereas the obliques are diagonal

Describe the superior oblique

Origin: body of the sphenoid (posterior wall of orbit)
Insertion: tendon passes around the trochlea in the superomedial cavity before inserting into the superolateral quadrant of the sclera
Primary action: intortion
Secondary action: depression and abduction
Innveration: trochlear nerve

Describe the inferior oblique

Origin: inferomedial orbital floor
Insertion: inferolateral sclera, posterior to lateral rectus
Primary action: extortion
Secondary action: elevation and abduction

What is the main arterial supply of the EOMs?

muscular branches of ophthalmic artery
- superior branch: superior rectus, superior oblique, levator palpebrae superioris and lateral rectus
- inferior branch: inferior rectus, inferior oblique abd medial rectus

What supplies the lateral rectus?

lacrimal artery

Describe the lacrimal gland

exocrine gland that secretes lacrimal fluid

What is the purpose of the lacrimal fluid?

cleans, nourishes, lubricates the eyes, as well as having antibacterial properties

Where is the lacrimal gland located?

superolateral orbit, within the lacrimal fossa of the frontal bone

What are the anatomical relations of the lacrimal gland?

Superior - zygomatic process of the frontal bone
Inferolateral - lateral rectus
Anterior - orbital septum
Posterior - orbital fat

What are two main parts of the lacrimal gland?

Orbital lobe and palpebral lobe

Describe the orbital lobe of the lacrimal gland

larger aspect
sits on the lateral margin of the levator palpebrae superioris

Describe the palpebral lobe of the lacrimal gland

smaller, comprised of lobules, located in the inner surface of the eyelid
acini produce lacrimal fluid

Where does the lacrimal fluid secreted by the acini of the palpebral gland go?

secreted through excretory ducts into superior conjunctival fornix where it is spread across the conjunctiva when blinking

What is the arterial supply of the lacrimal gland?

lacrimal artery

What is the venous supply of the lacrimal gland?

superior ophthalmic vein --> cavernous sinus

Where is lymphatic drainage from lacrimal gland?

superifical parotid lymph nodes (just above ear)

What innervates the lacrimal gland?

lacrimal nerve from the ophthalmic branch of the trigeminal nerve
- parasympathetic fibres stimulate fluid secretion
- sympathetic fibres inhibit fluid secretion

Describe the lacrimal apparatus

allows drainage of fluid via the medial canthus --> lacrimal sac via upper/lower lid puncta and canaliculus, where fluid travels down the nasolacrimal duct to the inferior meatus

What are the 3 main functions of the eyelids?

1. protection from excess light
2. protect eye form injury
3. lacrimal fluid distribution

What is the name of the location where the upper and lower eyelids meet?

medial and lateral canthi

What is the name of the opening between the two eyelids?

Palpebral aperture

What are the 5 main layers of the eyelids?

1. superficial: skin and subcutaenous tissue
2. orbicularis oculi
orbital septum (a fibrous barrier) follows but is not a layer
3. levator apparatus
4. tarsal plate
5. conjunctiva (touches eye)

Describe the skin and subcutaneous layer of the eyelid

contains eyelashes (cilia) from the anterior lid margin
associated with sweat glands (glands of Moll) and sebaceous glands (glands of Zeis)

Describe the orbicularis oculi

concentric bands of muscle with strong medial and lateral canthi ligament attachements
orbital and palpebral aspect
action --> tight and gentle closure of eyelids
innervated by the facial nerve (CN VII)

Describe the orbital septum

Extension of the periosteum (connective tissue around the orbit)
- seperates anterior lamella from posterior lamella
- blends with LPS (superior lid)
- inserts into the tarsal plate (inferior lid)
acts as a protective barrier against infection and inflammation

Describe the levator palpebrae superioris

solitary, striated muscle extended from facial tissue via levator aponeurosis
origin - lesser wing of sphenoid, immediately above optic foramen
insertion - superior tarsal plate of upper eyelid
action - elevation of upper eyelid
innveration - oculomotor nerve

Describe the superior tarsal muscle (Mullers muscle)

smooth muscle
originates from underside of LPS
inserts on superior tarsal plate
innervation: sympathetic fibres from internal carotid artery, passing within the oculomotor nerve

Describe the tarsal plate

Dense connective tissue posterior to orbicularis oculi, split into superior tarsus (upper lid) and inferior tarsus (lower lid) and acts as scaffolding

What are meibomian glands?

Sebaceous glands of the eyelids within tarsal plate
makes lacrimal fluid oily so it does not evaporate

What is the deepest layer of the eyelid?

palpebral conjunctiva

What supplies the eyelid?

External and internal carotid arteries

Describe the external carotid artery supply

facial artery --> angular artery: supplies medial lid
superficial temporal artery supples lateral lid

Describe the internal carotid artery supply

ophthalmic artery --> lacrimal, medial, palpebral, supraorbital, supratrochlear and dorsal nasal arteries: upper lid supply

Venous drainage of the eyelid

pre-tarsal system drains into the internal and external jugular veins
deeper system (post-tarsal) drains into the cavernous sinus

Describe the nerve supply to the eyelid

ophthalmic and maxillary branches of the trigeminal nerve
- also the mandibular branch