Head And Neck: Anatomy Of The Eye Flashcards
(24 cards)
Where is the lacrimal gland located?
Where does it drain into?
The lacrimal gland is located at the superior lateral border of the eye (eg the edge of the eyebrow)
It drains into the lacrimal canal at the corner of the eye into the nasolacrimal duct
What part of the orbit is the weakest?
The inferior border
What bones make up the boundaries of the orbit?
Roof = frontal and sphenoid Lateral = zygomatic and sphenoid Medial = ethmoid, maxillary, lacrimal and sphenoid Floor = maxillary and zygomatic
What are the foramen within the orbit?
The optic canal
Superior and inferior orbital fissures
What structures pass through each of the foramen?
Optic canal: optic nerve
Inferior orbital fissure: inferior ophthalmic vein
Superior orbital fissure: everything else inc V1 of trigeminal, abducens, occulomotor, trochlear
What are the 3 layers surrounding the eyeball?
Sclera: the outer fibrous layer which helps to keep shape. Turns into the cornea anteriorly
The choroid: the middle vascular layer, contains choroid, ciliary body and iris. Supplies nutrients to avascular structures eg lens and back of eye
The retina: the inner layer, consists of rods and cones that transmit light into nerve impulses
When looking at a photograph of the retina, how can you tell which eye it is?
The optic disc is always on the nasal side of the fundus (the picture)
What features can you see on a photo of the retina?
The optic disc
The fovea and macula (dark spot)
The blood vessels
Why anatomically does the retina tear first from trauma?
The sclera and choroid develop together therefore they are more strongly bounded together - so the retina will tear first
What is retinal detachment?
Can it be treated?
Occurs from trauma - the retina is torn away from the choroid.
It can be reattached surgically but w/o blood supply it is too late
What are the layers surrounding the optic nerve?
The pia mata, arachnoid mata and dura mata
(From inside out)
These are the same layers that surround the brain
Why does meningitis cause photophobia?
The dura mata surrounds the optic nerve so inflammation can irritate the optic nerve and cause photophobia
What are the chambers of the eye?
The eye can be split into an anterior segment (everything in front of the lens inc the lens) and the posterior segment
Anterior segment:
Anterior chamber contains aqueous humor and sits in front of the lens, the posterior chamber is either side of the lens
Posterior segment:
The vitreous body
What structure produces the aqueous humor?
How does the a humour drain?
The ciliary body produces the aqueous fluid
It drains via a trabecular mesh work
What pathology causes open angle glaucoma?
Why does this distort vision?
There is a blockage in the trabecular meshwork so the aqueous humour is unable to drain.
The pressure increases and presses on to the optic nerve at the back of the eye and distorts vision
Explain the mnemonic LR6 SO4 R3?
LR6: lateral rectus supplied by CN6
SO4: superior oblique supplied by CN4
R3: Rest of the muscles supplied by CN3
(Medial, superior and inferior rectus, inferior oblique, levator palpebrae superioris)
What is a blow out fracture?
Increased pressure in the eye (eg a punch) causes the inferior of the orbit to fall through.
The contents of the orbit fall down producing a ‘tear drop sign’ on xray
Why can someone with a blowout fracture not look up?
The inferior rectus muscle gets stuck in the fracture so tethers the eye down
What is the blood supply to the eye?
The ophthalmic artery (branch of the internal carotid)
Gives rise to the central retinal artery
What condition would cause a ‘cherry red spot on a pale background’ when looking through at ophthalmoscope?
Central retinal artery occlusion - the retina is ischaemic so appears pale
The macula and fovea are pigmented so appear red
What is the venous drainage of the eye?
The central retinal vein - drains into superior ophthalmic vein- drains into cavernous sinus
What is the conjuctiva?
A thin film surrounding the entire eyeball inc the iris and pupil
What are the structures in the eyelid?
Muscles: the levator palpebrae superioris and superior tarsal (accessory)
Glands:
Tarsal gland and ciliary gland (keep eyelid moist)
Palpebral conjuctiva
How do you test each of the extra-ocular muscles?
Superior rectus: look up and out Inferior rectus: look down and out Medial rectus: look in Lateral rectus: look out Superior oblique: look down and in Inferior oblique: look up and in
