PAS407 - Updated Study Material on Ocular Anatomy and Associated Nerves

superior wall of orbit:

frontal bone and lesser wing of sphenoid

medial wall of orbit:

ethmoid bone, maxilla, lacrimal, sphenoid bones

the trochlea is found in?

medial wall, superiorly

inferior wall of orbit:

maxilla, zygomatic, palatine bones

lateral wall of orbit:

formed by zygomatic, sphenoid

o strongest, thickest wall

what are the 3 supporting apparatuses of the eye?

1. fascial sheath

2. check ligaments

3. retrobulbar fat

what envelops the eyeball?

fascial sheath

o forms actual socket for eyeball

what does the fascial sheath of the eyeball do passively?

passively elevate/depress superior/inferior eyelids during upward/downward gaze

what helps with stabilization of the eye?

check ligaments

- limit abduction, adduction

what is the retrobulbar fat of the eye?

provides padding, support to resist posterior movement of eye during compression, muscle contraction

inophthalmos: what is it?

retraction of eyeball into orbit during periods of starvation, due to shrinking of retrobulbar fat

What is the lacrimal apparatus?

produces, distributes, and removes tears

what are the portions of the lacrimal apparatus? (3)

1. lacrimal gland

2. lacrimal canaliculi

3. nasolacrimal duct

what is the lacrimal gland?

Almond shaped gland tucked in superolateral lacrimal fossa

secretes lacrimal fluid

· watery physiological saline

· moistens, lubricates surfaces of conjunctiva, cornea

what is the lacrimal canaliculi?

drain lacrimal fluid to lacrimal sac (dilated superior part of nasolacrimal duct)

what is the nasolacrimal duct?

conveys lacrimal fluid to inferior nasal meatus in nasal cavity

describe the flow of fluid/tear production (5)

1. fluid production stimulated by parasympathetic impulses from facial nerve

2. eyelids come together in lateral-to-medial sequence, pushing fluid medially over cornea

3. drains by capillary action through lacrimal puncta, lacrimal canaliculi to lacrimal sac

4. fluid passes to inferior nasal meatus of nasal cavity through nasolacrimal duct.

5. drain posteriorly across floor of nasal cavity, eventually swallowed

what is the lacrimal sac?

provides passage of lacrimal fluid towards nasal cavity

what are the extraocular muscles of the orbit? (7)

Levator Palpebrae Superioris

lateral rectus

medial rectus

superior rectus

inferior rectus

inferior oblique

superior oblique

what do these muscles primarily work to do? where do they mostly originate?

· seven muscles work together to move superior eyelids, eyeballs.

· Most originate off common tendinous ring - fibrous cuff that surrounds optic canal, part of superior orbital fissure at apex of orbit

what muscle is associated with Horner's syndrome? (ptosis of the eyelid due to loss of sympathetic tone)

levator palpebrae superioris

this is because this muscle's primary function is to keep the eyelids open

levator palpebrae origin

roof of orbit

levator palpebrae insertion

upper eyelid

levator palpebrae action

elevates superior eyelid

levator palpebrae innervation

oculomotor nerve (CNIII)

lateral rectus origin

common tendinous ring

lateral rectus insertion

lateral surface of eye

lateral rectus action

abduction

lateral rectus innervation

abducens nerve

medial rectus origin

common tendinous ring

medial rectus insertion

medial surface of eyeball

medial rectus action

adduction

medial rectus innervation

Oculomotor nerve (CN III)

superior rectus origin

common tendinous ring

superior rectus insertion

superior surface of eyeball

superior rectus action

turns eyeball superiorly

superior rectus innervation

Oculomotor nerve (CN III)

inferior rectus origin

common tendinous ring

inferior rectus insertion

inferior eye

inferior rectus action

depresses eye

inferior rectus innervation

Oculomotor nerve (CN III)

inferior oblique origin

anteromedial floor of orbit

inferior oblique insertion

inferior, lateral surface of eyeball

inferior oblique action

Abducts, elevates, externally (extorsion) rotates the eye

inferior oblique innervation

oculomotor nerve

superior oblique origin

posterior orbit

superior oblique insertion

superior, lateral surface of eyeball

superior oblique action

abducts, depresses and internally (intorsion) rotates the eye

superior oblique innervation

trochlear nerve

what are the ocular muscles not innervated by the oculomotor nerve?

1. superior oblique m. -> trochlear n.

2. lateral rectus m. -> abducens n.

what are the main nerves of the orbit? (5)

1. optic nerve

2. oculomotor nerve

3. abducens nerve

4. trochlear nerve

5. opthalmic nerve

what does the oculomotor nerve do?

controls eye movement

what are the divisions of the oculomotor nerve and what do those divisions do? (2)

1. superior division

- supplies superior rectus, levator palpebrae superioris

2. inferior division

- supplies medial, inferior rectus, inferior oblique

- carries presynaptic parasympathetic fibers to ciliary ganglion, postsynaptic parasympathetic fibers to eye

where does the trochlear nerve pass?

medial surface of superior oblique muscle

where does the abducens nerve pass?

directly to inferior rectus muscle

what 3 branches does the Opthalmic nerve divide into, in the orbit? (Remember, the Opthalmic nerve is a branch of the trigeminal nerve)

1. frontal

2. nasociliary

3. lacrimal

where do the frontal, nasociliary, and lacrimal nerves pass through?

superior orbital fissure

what do the frontal, nasociliary, and lacrimal nerves supply?

supply structures related to anterior orbit (e.g., lacrimal gland, eyelids, face, scalp)

what artery mainly supplies the orbit?

Opthalmic artery

the ophthalmic artery branches from what?

internal carotid a.

what are the sub-arteries of the orbit? (3)

1. infraorbital a. (from external carotid)

2. central artery of retina (from ophthalmic artery)

3. short and long ciliary arteries

the venous drainage of the orbit is done through what veins?

1. superior ophthalmic vein

2. inferior opthalmic vein

where do the superior and inferior ophthalmic veins pass through?

superior orbital fissure

where do the superior and inferior vena cava veins empty?

cavernous sinus

Opthalmic nerve:

what two branches come off the frontal branch of the Opthalmic nerve?

1. supraorbital

2. supratrochlear

what does the Opthalmic nerve and its frontal branches supply?

skin of the forehead

Opthalmic nerve:

what branches come off the nasociliary branch of the Opthalmic nerve?

1. posterior ethmoidal

2. anterior ethmoidal

3. infratrochlear

what does the opthalmic nerve and it's nasociliary branches supply?

ethmoidal air cells, external nose, cutaneous bridge of nose

Optic canal

Superior orbital fissure

Fossa for lacrimal gland

Sphenoid bone

palatine bone

Ethmoid bone

Lacrimal bone

Zygomatic bone

Inferior orbital fissure

Maxilla

Palpebral Conjunctiva

Tarsus

Eyelashes

Orbital septum

Medial palpebral ligament

Lateral palpebral ligament

Inferior check ligament

Facial sheath

Retrobulbar fat

Lacrimal gland

Lacrimal gland

Lacrimal punctum

Lacrimal canaliculi

Nasolacrimal duct

Retina

Blood vessels

Fovea

Macula

Iris

Cornea

Pupil

Lens