Eye Part 2

Question 1

What are the hemisphere and quadrants of the eye ?

Answer 1

temporal - (lateral )

nasal - (near nose) - medial

Quadrants - superior temporal
superior nasal
Inferior temporal
inferior nasal

Question 2

Opthalmic a . an central retinal artery - supply of eye ?

Answer 2

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 )

Question 3

Opthalamic a. branches

Answer 3

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.

Question 4

importance of central retinal a. ?

Answer 4

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

Question 5

what is the optic nerve ?ttthhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

Answer 5

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.

Question 6

What is monocuar vision loss ?

Answer 6

complete loss of vision in one eye.

Question 7

What is scotoma ?

Answer 7

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.

Question 8

What is the optic radiation /?

Answer 8

Extends from lateral geniculate body to primary visual cortex in occiptal lobe.

Question 9

PITS

Answer 9

pits

parietal lobe tumour give rise to inferior quadrantanopia

PITS

P - Parietal lobe tumour

I - inferior quadrantanopia

T - temporal lobe lesion

S- superior quarantopia.

Question 10

What causes ipsilateral nasal hemianopia ?

Answer 10

the lateral (outside ) optic nerves run close to the Internal carotid a.

Aneurysm of ICA can compress the nerve

Question 11

What structures make up the eye orbits ?

-borders ?

Answer 11

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 .

Question 12

What are the pathways into the orbit ?

Answer 12

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.

Question 13

What are the types of orbital fractures are there ?

Answer 13

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

Question 14

Consequences of orbital fractures .?

Answer 14

0 increased intraorbital pressure ——————————————————————> Exophtamlos (protrusion on eye )

0 hemorrhage into neighboring sinus

Question 15

What is Exophtamlos & enophthalmos ?

• Causes

Answer 15

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.

Question 16

What are the axis of the eye - more than one ?

Answer 16

0 Orbital axis - line passes through apex of orbit (optical canal ) —————————–> to middle of anterior aspect of orbit.

0 Eyeball axis