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Anatomy + Conditions Of The Eye I Flashcards

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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
Key muscles within the eyelid
Palpebral part of orbicularis oculi Levator palpebrae superioris
26
What glands are located in the eyelids?
Meibomian glands Glands associated with lash follicle
27
Function of Meibomian glands
Modified sebaceous fluid Provide lipid layer of tear film Prevent tear evaporation + spillage over lid
28
What is released from glands in the eyelids?
Sebaceous fluid - oily substance
29
What glands are located in the tarsal place?
Meibomian glands
30
Describe a stye
- located on the outer part of eyelid - painful - red with white puncture
31
Treatment of stye
Warm compress +/- oral antibiotics
32
What causes a stye?
Infection *staphylococcus*
33
Describe a Meibomian cyst
- deeper within lid - painless - firm lump palpable which enlarges gradually
34
What causes a Meibomian cyst?
Blocked duct (Non infective)
35
Treatment of Meibomian cyst
1/3 resolve on their own Surgical incision if persists
36
What is blepharitis?
Inflammation of eyelid margin
37
Presentaiton of blepharitis
Crusting Dry eyelids +/- swollen + red
38
Treatment of blepharitis
Warm compress Lid hygiene
39
What conditions can affect the eyelids?
Stye Meibomian cyst Blepharitis
40
What are the lacrimal apparatus
Structures involved in tear film production + drainage
41
What are the layers of the tear film? Where are the layers secreted from?
Three layers: **Oily** - Meibomian gland **Water** - lacrimal gland **Mucous** - goblet cells
42
How is the position of the eyeball maintained?
- suspensory ligament - extra ocular muscles attach - orbital fat
43
How can retro-orbital pathology change the position of the eye?
Displaces globe anteriorly
44
What is the outer anterior surface of the eyeball covered with to the limbus)
Transparent conjunctival membrane (Not over the cornea)
45
What is the junction between the sclera + cornea?
Limbus
46
Presentation of conjunctivitis
- gritty feeling - watery +/- discharge
47
Three causes of conjunctivitis
Viral (most common) Bacterial Allergic
48
Describe subconjunctival haemorrhage?
- When a blood vessels breaks in the conjunctiva - Painless with no other symptoms
49
What are the layers of the eyeball?
- White **sclera** (outermost) - Vascular **choroid** - Photosensitive **retina** (innermost)
50
What is the uveal tract?
Choroid, iris + ciliary body are continuous
51
What does the sclera become as it reaches the anterior eye?
Cornea
52
What is the blood supply to the eye?
Ophthalmic artery
53
What is the blood supply to the retina?
- outer 1/3: **capillaries in the choroid** - inner 2/3: **central retinal artery**
54
What is the globe of the eye filled with?
- **Aqueous humor** (watery) anterior to lens - **Vitreous humor** (firm jelly-like) posterior to lens
55
What does the ciliary body contain?
Ciliary muscles Ciliary processes
56
Drainage of the aqueous humor
- produced by ciliary body - posterior chamber - anterior chamber - iridocorneal angle - trabecular mesh work into canal of Schlemm
57
What are the chambers of the aqueous humour?
- **anterior**: between cornea + iris - **posterior**:between iris + lens/ciliary body
58
What could a painful acute red eye be?
- **corneal injury** *e.g. abrasion, ulcer* - **keratitis**: inflamed cornea - **scleritis**: inflamed sclera - **uveitis**: inflamed uveal tract - **acute glaucoma**
59
What could a painless acute red eye be?
Conjunctivitis Subconjunctival haemorrhage
60
Complication of scleritis
Eyeball rupture as sclera thins
61
What is acute glaucoma?
Optic nerve damage secondary to raised intraocular pressure (inside the eyeball)
62
What produces the aqueous humor?
Ciliary body
63
What happens in acute glaucoma?
- narrowing of iridocorneal angle (closed angle) - aqueous humor cannot drain - increasing intraocular pressure - damage to optic nerve
64
Presentation of acute glaucoma
- older person - acutely painful red eye - blurred vision (due to corneal oedema) - irregular oval shaped pupil - N+V
65
Treatment of acute glaucoma
Medications to reduce pressure Then surgical treatment
66
Is acute or chronic glaucoma more common?
Chronic
67
What is chronic glaucoma?
Optic nerve damage secondary to raised intraocular pressure
68
What happens in chronic glaucoma?
- 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
What is seen on a fundoscopy in a patient with glaucoma?
Glaucomatous cupping (Larger bright yellow circle)
70
What is the macula + fovea in the eye?
Point of highest acquit vision (central vision)
71
Where are the photoreceptors located?
Deepest layer of the retina (Rods + cones)
72
What is the most common cause of blindness in the UK?
Macula degeneration
73
What does the macula look like during fundoscopy? Why?
Dark circle Thinnest part of retinal layer
74
What happens in a central retinal artery occlusion?
Sudden painless loss of vision in one eye over seconds *e.g. due to embolus causing occlusion* Amaurosis fugax
75
What would you see in a patient with a central retinal artery occlusion on fundoscopy?
- Pale retina due to ischaemia - small cherry red spot is the macula
76
Venous drainage of the orbit + eye
- **Superior ophthalmic vein** > to cavernous sinus - **Inferior ophthalmic vein** > to pterygoid venous complex
77
What is mydriasis?
Dilated pupil With no response to light

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