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HNN > Anatomy + Conditions Of The Eye I > Flashcards

Anatomy + Conditions Of The Eye I Flashcards

1
Q

Describe the orbital cavity

A
  • pyramidal shape with apex pointing posteriorly
  • four bony walls
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2
Q

Bones forming the orbital cavity

A

Frontal
Ethmoid
Lacrimal
Maxilla
Palatine
Zygomatic
Sphenoid

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3
Q

What are the weakest parts of the orbital cavity?
Why?

A
  • Inferior (floor) wall (maxillary bone)
  • Medial wall (ethmoid bone)
  • Not supported by solid bone
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4
Q

What happens in an orbital blowout fracture?

A
  • Sudden increases in intra-orbital pressure from trauma to eye/orbit which fractures the orbital floor
  • orbital contents prolapses > bleeding into maxilllary sinus
  • entrapment of tissues near orbital floor > prevents upwards gaze
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5
Q

Important anatomical relations to the orbit

A
  • anterior cranial fossa
  • ethmoid air cells (air sinuses)
  • maxillary air sinus
  • nasal cavity (via nasal lacrimnal duct)
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6
Q

Borders of the orbital cavity

A
  • roof: orbital plates of frontal bone
  • floor: maxilla bone
  • medial: ethmoid + lacrimal bones
  • lateral sphenoid + zygomatic bones
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7
Q

Management of orbital blowout fracture

A
  • CT of orbit
  • avoid nose blowing, valsalva manoeuvres + driving (until diplopia resolves)
  • surgical repair if symptoms persists 1-2 weeks post injury
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8
Q

What eye movement is restricted in orbital blowout fracture?
Why?

A

Upward gaze
Entrapment of the tissues near the orbital floor in fracture site

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9
Q

How does orbital cellulitis occur?

A
  • Ethmoidal air cells become infected (acute sinusitis)
  • infection can break through the thin lamina papyracea
  • infection spreads into orbit
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10
Q

What is the lamina papyracea?

A

Part of the ethmoid bone forming the medial wall of the orbit
‘Paper thin’

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11
Q

When does an orbital blowout fracture occur?

A

Sudden increased in intra orbital pressure from trauma to eye/orbit

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12
Q

Openings in the apex of the orbital cavity

A

Optic canal
Superior orbital fissure
Inferior orbital fissure

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13
Q

What structures pass through the optic canal?

A

Optic nerve
Ophthalmic artery

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14
Q

What structures pass through get superior orbital fissure?

A
  • oculomotor nerve III
  • trochlear nerve IV
  • abducens nerve VI
  • ophthalmic division of trigeminal nerve Va
  • superior ophthalmic vein (communicates with cavernous sinus)
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15
Q

What structures pass through the inferior orbital fissure?

A
  • infraorbital nerve (branch of Vb)
  • inferior ophthalmic vein (communicates with pterygoid venous plexus)
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16
Q

What nerve carries pain from the orbit?

A

Ophthalmic division of trigeminal nerve Va

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17
Q

What is the orbital septum?

A
  • Thin fibrous sheet originating from orbital rim
  • Separates intra-orbital contents from muscle + subcutaneous tissue of eyelid
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18
Q

What is the orbital septum continuous with?

A

Tarsal plate

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19
Q

Function of the orbital septum

A

Barrier against infection spreading from the superficial eye lid region (pre septal) into the orbital cavity (post-septal)

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20
Q

What is periorbital cellulitis?

A

Infection confined to skin + tissues of eyelid superficial to the orbital septum (pre-septal)

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21
Q

Affect of periorbital cellulitis on eye movement + vision

A

Eye movement + vision unaffected as it is outside the orbit

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22
Q

What is orbital cellulitis?

A

Infection within the orbit posterior or deep to the orbital septum (post-septal)

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23
Q

Presentation of orbital cellulitis

A

Proptosis
Reduced eye movements +/- pain
Reduced visual acuity

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24
Q

What does the eyelid consist of?

A

Skin
Subcutaneous tissue
Muscles
Tarsal plate

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25
Q

Key muscles within the eyelid

A

Palpebral part of orbicularis oculi
Levator palpebrae superioris

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26
Q

What glands are located in the eyelids?

A

Meibomian glands
Glands associated with lash follicle

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27
Q

Function of Meibomian glands

A

Modified sebaceous fluid
Provide lipid layer of tear film
Prevent tear evaporation + spillage over lid

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28
Q

What is released from glands in the eyelids?

A

Sebaceous fluid - oily substance

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29
Q

What glands are located in the tarsal place?

A

Meibomian glands

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30
Q

Describe a stye

A
  • located on the outer part of eyelid
  • painful
  • red with white puncture
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31
Q

Treatment of stye

A

Warm compress +/- oral antibiotics

32
Q

What causes a stye?

A

Infection
staphylococcus

33
Q

Describe a Meibomian cyst

A
  • deeper within lid
  • painless
  • firm lump palpable which enlarges gradually
34
Q

What causes a Meibomian cyst?

A

Blocked duct
(Non infective)

35
Q

Treatment of Meibomian cyst

A

1/3 resolve on their own
Surgical incision if persists

36
Q

What is blepharitis?

A

Inflammation of eyelid margin

37
Q

Presentaiton of blepharitis

A

Crusting
Dry eyelids
+/- swollen + red

38
Q

Treatment of blepharitis

A

Warm compress
Lid hygiene

39
Q

What conditions can affect the eyelids?

A

Stye
Meibomian cyst
Blepharitis

40
Q

What are the lacrimal apparatus

A

Structures involved in tear film production + drainage

41
Q

What are the layers of the tear film?
Where are the layers secreted from?

A

Three layers:
Oily - Meibomian gland
Water - lacrimal gland
Mucous - goblet cells

42
Q

How is the position of the eyeball maintained?

A
  • suspensory ligament
  • extra ocular muscles attach
  • orbital fat
43
Q

How can retro-orbital pathology change the position of the eye?

A

Displaces globe anteriorly

44
Q

What is the outer anterior surface of the eyeball covered with to the limbus)

A

Transparent conjunctival membrane
(Not over the cornea)

45
Q

What is the junction between the sclera + cornea?

46
Q

Presentation of conjunctivitis

A
  • gritty feeling
  • watery +/- discharge
47
Q

Three causes of conjunctivitis

A

Viral (most common)
Bacterial
Allergic

48
Q

Describe subconjunctival haemorrhage?

A
  • When a blood vessels breaks in the conjunctiva
  • Painless with no other symptoms
49
Q

What are the layers of the eyeball?

A
  • White sclera (outermost)
  • Vascular choroid
  • Photosensitive retina (innermost)
50
Q

What is the uveal tract?

A

Choroid, iris + ciliary body are continuous

51
Q

What does the sclera become as it reaches the anterior eye?

52
Q

What is the blood supply to the eye?

A

Ophthalmic artery

53
Q

What is the blood supply to the retina?

A
  • outer 1/3: capillaries in the choroid
  • inner 2/3: central retinal artery
54
Q

What is the globe of the eye filled with?

A
  • Aqueous humor (watery) anterior to lens
  • Vitreous humor (firm jelly-like) posterior to lens
55
Q

What does the ciliary body contain?

A

Ciliary muscles
Ciliary processes

56
Q

Drainage of the aqueous humor

A
  • produced by ciliary body
  • posterior chamber
  • anterior chamber
  • iridocorneal angle
  • trabecular mesh work into canal of Schlemm
57
Q

What are the chambers of the aqueous humour?

A
  • anterior: between cornea + iris
  • posterior:between iris + lens/ciliary body
58
Q

What could a painful acute red eye be?

A
  • corneal injury e.g. abrasion, ulcer
  • keratitis: inflamed cornea
  • scleritis: inflamed sclera
  • uveitis: inflamed uveal tract
  • acute glaucoma
59
Q

What could a painless acute red eye be?

A

Conjunctivitis
Subconjunctival haemorrhage

60
Q

Complication of scleritis

A

Eyeball rupture as sclera thins

61
Q

What is acute glaucoma?

A

Optic nerve damage secondary to raised intraocular pressure (inside the eyeball)

62
Q

What produces the aqueous humor?

A

Ciliary body

63
Q

What happens in acute glaucoma?

A
  • narrowing of iridocorneal angle (closed angle)
  • aqueous humor cannot drain
  • increasing intraocular pressure
  • damage to optic nerve
64
Q

Presentation of acute glaucoma

A
  • older person
  • acutely painful red eye
  • blurred vision (due to corneal oedema)
  • irregular oval shaped pupil
  • N+V
65
Q

Treatment of acute glaucoma

A

Medications to reduce pressure
Then surgical treatment

66
Q

Is acute or chronic glaucoma more common?

67
Q

What is chronic glaucoma?

A

Optic nerve damage secondary to raised intraocular pressure

68
Q

What happens in chronic glaucoma?

A
  • the trabecular mesh work into canal of schlemm deteriorates with age
  • pressure slowly rises
  • gradual loss of peripheral vision
    (No issue with iridocorneal angle - open angle glaucoma)
69
Q

What is seen on a fundoscopy in a patient with glaucoma?

A

Glaucomatous cupping
(Larger bright yellow circle)

70
Q

What is the macula + fovea in the eye?

A

Point of highest acquit vision (central vision)

71
Q

Where are the photoreceptors located?

A

Deepest layer of the retina
(Rods + cones)

72
Q

What is the most common cause of blindness in the UK?

A

Macula degeneration

73
Q

What does the macula look like during fundoscopy?
Why?

A

Dark circle
Thinnest part of retinal layer

74
Q

What happens in a central retinal artery occlusion?

A

Sudden painless loss of vision in one eye over seconds
e.g. due to embolus causing occlusion
Amaurosis fugax

75
Q

What would you see in a patient with a central retinal artery occlusion on fundoscopy?

A
  • Pale retina due to ischaemia
  • small cherry red spot is the macula
76
Q

Venous drainage of the orbit + eye

A
  • Superior ophthalmic vein > to cavernous sinus
  • Inferior ophthalmic vein > to pterygoid venous complex
77
Q

What is mydriasis?

A

Dilated pupil
With no response to light

HNN (24 decks)

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