HNS 6 - Eye and Orbit Flashcards
List the bones of the orbit
- Roof is the orbital plate of the frontal bone
- The floor is the orbital plate of the maxilla
- Laterally there is the zygoma and the greater wing of the sphenoid
- Medial wall is made of the frontal process of the maxilla, lacrimal bone, orbital plate of ethmoid, and lesser wing of the sphenoid
List the optic foramina
- Optic canal (optic nerve and ophthalmic artery)
- Inferior orbital fissure (maxillary nerve and infraorbital vessels)
- Superior orbital fissure (ophthalamic nerve, oculomotor, trochlear, abducens nerves, ophthalmic vessels and sympathetic fibres)
Where is the optic canal?
Embedded in the lesser wing of the sphenoid bone
Where is the superior orbital fissure?
Between the greater and lesser wings of the sphenoid bone
Where is the inferior orbital fissure?
Below the greater wing of the sphenoid bone
List the recti muscles
- Inferior
- Superior
- Medial
- Lateral
Where do the recti muscles origionate?
Common tendinous ring
Where do the recti muscles insert?
Sclera (5mm behind the corneal margin)
Describe the nerve supply of the recti
- Inferior superior and medial is oculomotor
- Lateral is abducens
List the oblique muscles of the eye
- Inferior
- Superior
Describe the origin of the oblique muscles of the eye
- Inferior: orbital surface of maxilla
- Superior: body of sphenoid
Where do the oblique muscles insert?
- Inferior: posterior inferior quadrant
- Superior: posterior superior quadrant via the trochlea (temporal side)
Describe the nerve supply of the obliques
- Internal oculomotor
- Superior by trochlear nerve
What is the levator palpebrae superioris?
Muscle of the upper eyelid
What is the origin of the levator palpebrae superioris?
Lesser wing of sphenoid
What is the insertion of the levator palpebrae superioris?
- Superior tarsal plate
- Skin of eyelid
Describe the nerve supply of the levator palpebrae superioris
- Oculomotor nerve
- Sympathetic to smooth muscle (Horners syndrome)
What is the trochlea of the orbit?
The bone that permits contraction of the superior oblique muscle
What is the common tendinous ring of the orbit?
- Where the recti muscles originate from
- Optic nerve passes through here
List the isolated muscle actions of each muscle of the eye
- Lateral rectus abduction
- Medial rectus adduction
- Superior oblique depressor and abductor
- Inferior oblique is an elevator and abductor
- Superior rectus adduction and elevation
- Inferior rectus abduction and depression
How are muscle actions tested clinically?
- Lateral rectus and medial rectus - abduct and adducting. Testing opposite muscle in each eye
- Adduct the eye then ask the patient to look down (superior oblique) and up (inferior oblique)
- Abduct the eye then ask to look down (inferior rectus) and up (superior rectus)
List the nerves of the orbit
- Optic (ganglion cell axons)
- Oculomotor (two rami - motor to MR, SR, IR, IO, LPS as well as parasympathetic constrictor fibres)
- Trochlear (motor to SO)
- Abducens (motor to LR)
List the branches of the opthalmic division of the trigeminal nerve
- Frontal (supratrochlear and supraorbital supplies innervation to the forehead)
- Lacrimal (supplies the lacrimal gland)
- Nasociliary (branch of ciliary ganglion, ethmoidal and infratrochlear)
Where is the cavernous sinus?
- Either side of the sphenoid bone
- Internal carotid artery
- Where the nerves pass before they enter the orbit
Describe the arrangement of nerves in the cavernous sinus
- Oculomotor nerve, trochlear nerve, ophthalamic division of the trigeminal nerve, and maxillary division of the trigeminal nerve are all on the lateral wall
- Abducens runs alongside the internal carotid artery
What is the importance of the nerves in the cavernous sinus?
They will all be damaged by a infection of the cavernous sinus
Describe the parasympathetic innervation of the eye
- Ciliary ganglion
- Preganglionic fibres in inferior ramus of oculomotor
- Postganglionic in short ciliary nerves
- Sphincter pupillae and ciliary muscle
Describe the blood supply of the eye
- Opthalmic artery (central artery, muscular branches, ciliary, lacrimal, supratrochlear and supraorbital branches)
- Opthalmic veins (superior joins back into the cavernous sinus ROUTE OF INFECTION, and inferior joins into the pterygoid plexus)
Describe the lacrimal system
- Lacrimal gland is in the anterolateral superior orbit, passes via the parasympathetic secretomotor fibres are from the facial nerve (from pterygopalatine ganglion via zygomaticotemporal and lacrimal nerves)
- Lacrimal sac drains via the lacrimal duct into the inferior meatus of the nose
