2-32,33 Orbit

Question 1

Describe the orbital floor
- What bones make it up?
- Damage?

Answer 1

Orbital portion of zygomatic bone + maxillary bone + orbital process of palatine bone
- Post. medial portion of maxillary bone is relatively weak so blunt force trauma usually fractures this. If breaks, things can leak from orbit to maxillary sinus

Question 2

Describe the orbital roof
- What bones make it up?
- Damage?

Answer 2

orbital plate of frontal bone + lesser wing of sphenoid bone.
- Thin + fragile

Question 3

Describe the orbital lateral wall
- What bones make it up?
- Damage?

Answer 3

Zygomatic bone + greater wing of sphenoid bone
- Thickest and strongest wall of the orbit
- Separated from orbital floor by inferior orbital fissure
- Still susceptible to damage due to eyeball protrusion past margin of wall

Question 4

Describe the orbital medial wall
- What bones make it up?
- Damage?

Answer 4

Maxillary bone + Lacrimal bone + Ethmoid bone + Sphenoid bone (both lesser + greater wings)
- Paper thin (ethmoid is thinnest). If fracture, orbit content leak to ethmoid sinus.
Note: Notches and grooves allow different structures to pass through.

Question 4

Describe the optic canal and orbital fissure
- Where is it?
- What does it contain?

Answer 4

Optical canal:
- Within lesser wing of sphenoid
- Sometimes called optical foramen
- Transmits optic nerve and ophthalmic artery
Orbital fissure:
- Kinda resembles NZ, separated into sup. and inf.
- Sup. Contains:
– Lacrimal nerve
– Frontal nerve
– Trochlear nerve
– Sup. Division of ocular motor nerve
– Nasocillary nerve
– Inf. Division of ocular motor nerve
– Abducens nerve
– Also has sup. And inf. Ophthalmic vein
- Sup. orbital fissure also divided into two parts: Sup. and Inf. Depending on where annulus of Zinn is (which makes up recti muscles)
- Inferior Orbital Fissure has nerves + BVs that go through that supply stuff around the eye.

Question 5

Generaly symptoms of orbital involvement?

Answer 5

• Red + watery + painful eye (pain w/ movement = EOM)
• Lid or conj. swelling
• Double/blurry vision (EOM)
• Changing eye appearance
• Pulsating sensation/tinnitus (abnormal blood flow in orbit)

Question 6

Signs of soft tissue involvement?

Answer 6

• Eyelid + periocular oedema -> “ptosis”
• Ecchymosis (bruising) (from BV leakage)
• Conj. chemosis
• Epibulbar injection (inflammation spills over anteriorly)

Question 7

Describe proptosis/exophthalmos
- What is it?
- How much?
- 2 types?

Answer 7

• Abnormal protrusion of eye
• Uni or bilateral
• > 20mm (bony prominence of lateral margin to corneal apex)
• Axial (more likely at annulus of Zihn) or eccentric (more likely outside annulus)

Question 8

Methods of measuring proptosis?
- Different types measured how?

Answer 8

Axial proptosis:
- Regular ruler
- Luedde exophthalmometer (edge can fit lateral canthus)
- Hertel exophthalmometer (Bar w/ 2 side attachments that align to lateral canthi)

Dystopia horizontal:
- Use regular ruler and take from middle of nose bridge to medial limbus

Dystopia vertical:
- Use 2 rulers. One horizontal on nose bridge, other measures from canthus to apex

Question 9

Describe Enophthalmos

Answer 9

• Eye goes backwards into globe
• Uni or bilateral
• Pseudo-ptosis possible
• > 2-3mm difference between eyes
• Axial or eccentric

Question 10

Describe Ophthalmoplegia
- How to test it?

Answer 10

• EOM paralysis (can be more than one)
• Either restrictive or neurological
  Forced duction test:
• Under anaesthesia, forcefully pull EOM and feel if restricted (+ve result)
  Differential IOP:
• Measure IOP at different gazes
• > = 6mmHg difference = +ve result = restrictive (normally, small increases can be seen)

Question 11

Fundus changes in orbital diseases?

Answer 11

• ONH swelling
• Optic atrophy
• Optocilliary shunts
• Choroidal folds