Eye Part 2 Flashcards
What are the hemisphere and quadrants of the eye ?
temporal - (lateral )
nasal - (near nose) - medial
Quadrants - superior temporal
superior nasal
Inferior temporal
inferior nasal
Opthalmic a . an central retinal artery - supply of eye ?
Ophthalmic artery - branch of internal carotid artery
0 arises directly after carotid sinus.
then passes through optic foramen —– > optic canal (with optic nerve) —–> course inferiolaterally to optic nerve ——- > crosses over (rarely under) optic nerve switching from lateral to medial. —— > merges from optic canal —— > divides into branches
Ophthalmic artery gives off 10 branches :
- central
retinal artery - 1st branch - supplies optic nerve & inner 6/7 layers of retina. (first branch gives off just before crossing of ophthalmic a. across optic nerve within optic canal )
Opthalamic a. branches
DR MCLESSI - has 2 terminal branches.
D - Dorsal nasal - terminal branch a. - supply nasalacrimal sac and dorsum of nose.
R - rentinal a. (central )
M - Muscular a. - supply extraocular muscles (superior rectus etc. )
C - Cillary arteries (posterior ) - 2 sets - long and short - supply sclera (white of the eye ) on posterior aspect of eyeball.
L - Lacrimal a. supplies lacrimal gland , eyelids , conjunctiva and art of dura mater.
E - ethmoid a. - anterior and posterior
0 anterior - anterior and medial ethmoid cells and nasal septum
0 Posterior - posterior ethmoid cells and nasal septum , lateral wall of nasal cavity.
S - Supraorbital a. - supplies superior rectus and levator palpbrae.
S -
supratrochlear a.
0 terminal
branch of
opthalamic
a. - supplies
skin ,
muscles and
periosteum (
protective
sheath
covering
outer surface
of bone ) of
forehead.
I - Internal palpebral a.
importance of central retinal a. ?
Occlusion - central retinal a occlusion - due atherosclerosis , blood clot.etc.
retina - contains cone and photo receptors.
medical emergency - needs to be treated early.
Terminal branches of central retinal a. are end arteries (end artery - artery is the only supply to a portion of tissue ) - occlusion of these will completely cut off blood circulation and result in :
0 Rapid
ischemia
0 infarction
0 complete
blindness
complete blindness
what is the optic nerve ?ttthhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
Cranial nerve 2
formed from outpocketing of fore brain - directly derived from brain - part of CNS and surrounded by cranial meninges and CSF.
Because it is surrounded by CSF
Increased intracranial pressure - can cause CSF to bulge out and cause visual disturbance - in the form of Papilledema
Papilledema - swelling of optic nerve as it enters the back of eye at optic disc.
What is monocuar vision loss ?
complete loss of vision in one eye.
What is scotoma ?
scotoma - focus area of visual loss or disturbance.
Central scotoma - blind spot in central vision.
- Can happen when there is partial damage to optic nerve before chiasm and crossing over.
What is the optic radiation /?
Extends from lateral geniculate body to primary visual cortex in occiptal lobe.
PITS
pits
parietal lobe tumour give rise to inferior quadrantanopia
PITS
P - Parietal lobe tumour
I - inferior quadrantanopia
T - temporal lobe lesion
S- superior quarantopia.
What causes ipsilateral nasal hemianopia ?
the lateral (outside ) optic nerves run close to the Internal carotid a.
Aneurysm of ICA can compress the nerve
What structures make up the eye orbits ?
-borders ?
orbit -pyrimidal structure -
o apex
(posterior
- opening
to optic
canal)
o base -
anteriorly
0 Roof - (superior ) Frontal bone and lesser wing of sphenoid bone.
0 Lateral - zygomatic bone & greater wing of sphennid bone
0 Floor - (inferior ) maxilla , palatine , zygomatic bones.
0 Medial wall - Maxilla , ethmoid , lacrimal & sphenoid bone ————- ethmoid separates orbit from ethmoid sinus
0 apex - opening of optic canal - optic foramen
0 base -bounded by eyelids -oribital rim .
What are the pathways into the orbit ?
Optic canal – transmits the optic nerve and ophthalmic artery.
Superior orbital fissure – transmits the
0 lacrimal,
0 frontal,
0 oculomotor (CN III (3)
0 trochlear (CN IV - 4)
0 abducens (CN VI - 6) nerves.
0 Nasocillary
0 superior ophthalmic vein.
Inferior orbital fissure – transmits the zygomatic branch of the maxillary nerve,
- the inferior ophthalmic vein
- sympathetic nerves.
What are the types of orbital fractures are there ?
0 Orbital rim fracture – fracture of the bones forming the outer rim of the bony orbit.
- It usually occurs at the sutures joining the three bones of the orbital rim – the maxilla, zygomatic and frontal.
0 Blow out fracture - partial herniation of the orbital contents through one of its walls.
- usually occurs via blunt force trauma to the eye.
The medial and inferior walls are the weakest, orbital content herniates into :
o ethmoid sinus - through medial wall
o maxillary sinus - through inferior wall
Consequences of orbital fractures .?
0 increased intraorbital pressure ——————————————————————> Exophtamlos (protrusion on eye )
0 hemorrhage into neighboring sinus
What is Exophtamlos & enophthalmos ?
- Causes
Exopthalmos (proptosis ) - protrusion of eye caused by:
o Graves
disease -
hyperthyroidism
- swelling of
muscle & fat -
autoimmune
attack -
o orbital
fracture
0 Enopthalmos - withdrawal of eyeball deep into socket.
o causes :
loss of fat due
to starvation
prolonged
illness or old
age.
