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Head and neck > Lecture 15– The Eye: Orbit and Lacrimal apparatus (Pt1) > Flashcards

Lecture 15– The Eye: Orbit and Lacrimal apparatus (Pt1) Flashcards

1
Q

orbital cavities

A

x2

  • Pyramidal shaped with apex pointing posteriorly and medially
  • House eye balls, extraocular eye muscles, lacrimal apparatus, fat, nerves, blood vessels
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2
Q

how many walls does the orbital cavity have

A
  • 4 walls
    • Lateral
    • Medial
      • Mostly the ethmoid and lacrimal bone
    • Roof
    • Floor
      • Mostly the maxillary
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3
Q
  • Base of pyramid faces
A

anteriorly- tough orbital rim

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4
Q

number of openings into/out of orbit

A
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5
Q

main arterial supply to orbit

A
  • Ophthalmic artery (first branch off the internal carotid sinus after cavernous sinus) and subsequent branches
    • Comes into the eye via the optic canal
    • Including central retinal artery
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6
Q

Main venous supply of the orbit

A
  • Ophthalmic veins (superior and inferior)
  • Drains venous blood into cavernous sinus, pterygoid plexus and facial vein
  • Via the superior and inferior orbital fissures
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7
Q

Nervous supply of contents of orbit

A
  • Special sensory vision from retina- Optic nerve – CN II
  • General sensory (touch, pain) from the eye (including conjunctive and cornea)- Ophthalmic division of Trigeminal nerve- CN Va
  • Motor nerves to muscles (extraocular muscles)
    • Oculomotor
    • Trochlear
    • Abducens
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8
Q

the floor of the orbita has a close anatomical relationship

A

inferiorly with the maxiallary air sinues (paranasal air sinus)

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9
Q

medial wall has a close anatomical relationship with

A

ethmoid bone

  • Air filled cavities near the ethmoid (paranasal air sinus)
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10
Q

roof has a close anatomical relationship with

A
  • rbital plates of frontal bone
    • Superior relationship- anterior cranial fossa and forntal lobe house within it
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11
Q

another important anatomical relation of the orbit

A
  • Nasal cavity also important anatomical relationship- connection between the orbit and nasal cavity by the nasolacrimal duct

Implications for: orbital trauma and spread of infection

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12
Q

……….. and ………….of orbit are the weakest parts of the orbital cavity

A

Medial wall and floor of orbit are the weakest parts of the orbital cavity

  • Ethmoid and maxillary bone have paranasal air sinuses- more prone to fracture
  • Floor of orbit weakest
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13
Q

orbital blow out fracture

A
  • Sudden increase in infraorbital pressure (e.g. from retropulsion of eye ball (globe) by fist or ball) fractures floor of orbit (maxilla)
  • Opacity= blood
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14
Q

CT and x-ray of orbital blow out fracture

A
  • Orbital content can prolapse and bleed into maxillary sinus
  • Fracture site can trap structures e.g. soft tissue extraocular muscle located near orbital floor
  • Prevents upward gaze on affected side
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15
Q

presentation of orbital blow out fracture

A
  • hisotry of trauma to the eye/orbit
  • periorbital swelling\
  • painful
  • double vision- worse on vertical gaze
  • numbness over cheek, lower eyelid and upp lip (and upper teeth ad gums) on effacted side
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16
Q

eyelids function

A

protect the eye

17
Q

eyelids are made up of a number of different tissues

A
  • Skin (most superficially)
  • Loose subcutaneous tissue
  • Orbicularis oculi (palpebral part)- CN VII)
    • Protects front of eye
  • Tarsal plate
  • Levator palpebrae superioris muscle
    • Arises from within orbital cavity and swings forwards anterior becomes aponeurotic and blends into tissue of upper eyelid
    • Retracts and elevates eyelid
    • Small smooth muscle components- mullers muscle- small contribution to elevation of the lid via sympathetic action
    • Bulk of muscle- CN III – oculomotor
  • Glands (contribute to tear film)
    • Prevents damage
      • Meibomian glands
      • Sebaceous glands associated with lash follicle
    • These can become blocked problems related to eyelids
18
Q

stye

A

sebaceous gland blockages

  • Superficial blockage
  • Painful lump usually in upper eyelid
  • White head
  • Localised infection – staphylococcus
19
Q

chalazian

A
  • Meibomian gland cyst
    • Deeper blockage
  • Painless
  • Not caused by infection
  • Just blockage
  • 1/3 resolve of on own
  • Treatment: warm compress and cleaning along eyelid margin
  • No Abx
20
Q
  • Blepharitis
A
  • Blockage of glands along the eyelid margin
  • More extensive
  • Less of a localised lump
  • Gritty crusting along eyelid margin
  • Simple eyelid hygiene
    • Warm compress
    • Margin
    • Cleaning
21
Q

Orbital septum

A

Thin sheet of fibrous tissue originating from orbital rim periosteum blends with tarsal plates

22
Q
  • Orbital septum and tarsal plates
A
  • separate subcutaneous tissue of eyelid and orbicularis oculi muscle from infraorbital contents
  • Acts as a barrier against superficial infection spreading from the pre-septal dn post-septal space (orbital cavity proper)
23
Q

Periorbital (pre-septal) cellulitis

A

Infection occurring within eyelid tissue, superficial to orbital septum

  • Secondary to superficial infection e.g. bites, wounds
  • Confined to tissues superficial to orbital septum and tarsal plates
  • Therefore:
    • Ocular function- eye movement and vision remains unaffected
  • Can be difficult to differentiate between peri-orbital and more severe orbital cellulitis
  • If in doubt refer urgently- high dose IV antibiotics and surgical drainage
24
Q

Orbital (post-septal) cellulitis

A

Infection WITHIN the orbit posterior or deep to the orbital septum

  • Can arise from pre-septal cellulitis
  • Usually arises from infection from within the orbit
  • Signs
    • Proptosis/ exophthalmos- eye pushed forward
    • Reduced +/- painful eye movement
    • Reduced visual acuity (optic nerve involved)
  • Most dangerous
    • Inferior and superior ophthalmic veins can spread infection to the cavernous sinus causing intracranial infections
      • Varbous sinus thrombosis
      • Meningitis
    • Treatment
      • Abx
      • Surgery
25
Q

postseptal (orbital) is

A

risk to optic nerve (sight threatening) - risk of intracranial spread

26
Q

Contents of orbital cavity

A
  • Nerve sand blood vessels
  • Fat +++
  • Lacrimal apparatus-production and drainage of tears
  • Eyeball (globe)
  • Extraocular muscles
27
Q

situation of the eyeball (globe)

A
  • Globe does not sit on the floor of the orbit
28
Q

eyeball position maintained by

A
  • Suspensory ligament of lockwood- sits under like a sling
  • Extraocular muscles
  • Orbital fat ++
29
Q

Tear film and lacrimal apparatus

Refers to

A

structures involved in tear film production and drainage

30
Q

tear film is

A

Important fluid to ensure anterior surface of the eye (conjunctiva and cornea) are kept lubricated and hydrated

  • Protects surface of the eye
31
Q

how does the tear film protext the surface of the eye

A
  • Blinking washes film over eye and washes debris away
32
Q

tear film has how many layers

A

oily

water

mucus

33
Q

which gland is responsible for the oil in the tearfilm

A

meibomian glands- within tarsal plates of upper and lower eyelids

34
Q

which gland is responsible for the water in the tearfilm

A

lacrimal gland -found deep to the orbital septum, closely related to the lateral edge of the Levator palpebral superioris

35
Q

which cell is responsible for the mucus in the tearfilm

A

goblet cells within the conjunctiva- transparent membrane over surface of the eye

36
Q
  • Drainage of tear film through
A

small ducts made up of the lacrimal punctum (which you can see if you pull inferior tarsal plate down) and the lacrimal canaliculus which drains into the nasolacrimal duct

37
Q

Obstruction of the lacrimal apparatus

*

A
  • Injury to medial aspect of eye
    • Scarring and fibrosis – obstruct drainage
    • Leads to overflow of tears over lower eyelid- epiphora.

Head and neck (51 decks)

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