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Head and Neck > Anatomy of the Orbit and Eye > Flashcards

Anatomy of the Orbit and Eye Flashcards

1
Q

Pathology affecting the bony orbit arteries and nerves

A

Orbital blow out

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2
Q

Pathology affecting eyelids

A

Stye

Meibomian cyst

Blepharitis

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3
Q

Pathology affecting orbital septum

A

Pre or post septal cellulitis

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4
Q

Pathology affecting lacrimal apparatus

A

Blockage

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5
Q

Pathology affecting eyeball

A

Acute red eye

Central retinal artery occlusion

Glaucoma

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6
Q

Describe the shape of the orbital cavity

A

Pyramidal shaped with apex pointing posteriorly (deepest part within head)

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7
Q

Bones forming the orbit

A

Frontal bone
Ethmoid bone
Lacrimal bone
Sphenoid bone
Zygomatic bone
Maxilla

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8
Q

What forms the 4 walls of the orbit?

A

Medial - ethmoid bone

Base pyramid (most anterior) - tough orbital rim

Floor - Maxillary

Roof - orbital plates of frontal bone

Lateral - Zygomatic bone

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9
Q

Weakest parts of orbit

A

Floor and medial wall - ethmoid bone and maxilla have air sinuses making them weaker

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10
Q

What lies directly above the orbit?

A

The anterior cranial fossa

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11
Q

What lies directly medial to orbit?

A

Ethmoid air cells (sinuses) within ethmoid bone

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12
Q

What lies directly below orbit?

A

Maxillary air sinus (within maxillary bone)

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13
Q

What does the orbit connect to?

A

Nasal cavity - via the nasolacrimal duct (boney channel)

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14
Q

What do these anatomical relations, alluded to above, mean for the orbit?

A

Means there are implications with orbital surgery

Spread of infection - sinusitis involving ethmoid sinus can spread into orbit

Orbital trauma (could even affect frontal lobe as just above?)

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15
Q

What occurs in an orbital blowout fracture?

A

Trauma directly to anterior eye - usually with fist/ball

Eye is propelled into back of socket towards apex (retropulsion)

This causes increase in intraocular pressure = fractures floor of orbit (maxilla, weakest part)

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16
Q

What happens following orbital blow out fracture?
+Implications of this:

A

Orbital contents prolapse and bleed into maxillary sinus

Soft tissue and muscles near fracture can also trap within the fracture site.

This can prevent upward gaze (and other eye movements)

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17
Q

Why does intraocular pressure increase in orbital blowout fracture?

A

Squeezing eyeball into smaller area (apex remember triangle shape of cavity)

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18
Q

Why can orbital blowout affect eye movements?

A

Extraocular muscles attach to underside of sclera and around sclera

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19
Q

Presentation of orbital blowout fracture

A

History of trauma to eye
Swelling
Painful
Periorbital swelling + bruising
Double vision - worse on vertical gaze
Numbness over cheek, lower eyelid and upper lip

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20
Q

Why do you get numbness or cheek, lower eyelid and upper lip in OBF?

A

Maxillary division of trigeminal nerve is damaged (runs in close proximity to base of orbit, infra orbital branch runs through inferior orbital fissure)

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21
Q

What will pt do on eye affected in OBF if asked to look up?

A

Eye affected will be unable to elevate

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22
Q

Management for orbital blowout fracture

A

CT orbit - refer to opthalmology
Prophylactic abx
Avoid nose blowing, driving (until dipoplia resolves)

Follow up in 1 week - if resolved symptoms, no treatment needed (oedema decreases, resolves)

If symptoms persist - may need surgical repair

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23
Q

Orbital cavity openings

A

Optic canal
Superior orbital fissure
Inferior orbital fissure

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24
Q

What goes through optic canal?

A

Optic nerve
Ophthalmic artery (+ branches and central retinal artery)

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25
Q

What goes through superior orbital fissure?

A

Ophthalmic division of trigeminal nerve
CN III - oculomotor
CN IV - trochlear
CN VI - abducens

Superior ophthalmic vein (communicating with cavernous sinus)

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26
Q

What goes through inferior orbital fissure?

A

Infraorbital nerve (branch of maxillary trigeminal nerve)

Inferior ophthalmic vein (communicating with pterygoid venous plexus)

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27
Q

Sensation of pain to eye nerve supply is…

A

Ophthalmic division of trigeminal nerve

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28
Q

Main blood supply to orbit and eye

A

Ophthalmic artery - first branch of internal carotid artery

Central retinal artery (branch of ophthalmic, supplies retina)

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29
Q

Main venous drainage of orbit and eye

A

Ophthalmic veins (superior and inferior)

Connecting to cavernous sinus, facial vein and pterygoid plexus

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30
Q

Where does the central retinal artery run?

A

Within the optic nerve

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31
Q

What does it mean that orbit communicates with cavernous sinus?

A

Route for infection to run extracranially to intracranial

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32
Q

Two arterial supplies to retina

A

Choroid layer (underlies it)
Central retinal artery

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33
Q

Blood supply to choroid layer

A

Ciliary arteries (posterior and anterior)
Feed capillary bed within choroid layer - choriocapillaries

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34
Q

Can the retina just rely on one supply (central retinal or choroid layer) at any one time?

A

NOOO - needs both otherwise will not function properly

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35
Q

Function of eyelid

A

Protects the eye

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36
Q

What does eyelid consist of?

A

Skin
Subcutaneous tissue
Muscles
Tarsal plate

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37
Q

Key muscles within eyelid

A

Orbicularis oculi - palpebral part, closes eyelid, supplied by facial nerve

Levator palpebrae superioris - retracts eyelid, skeletal supplied by oculomotor, smooth muscle (superior tarsal) supplied by sympathetic.

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38
Q

Other muscles present around orbit area

A

Frontalis
Mullers muscle

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39
Q

Tarsal plate structure

A

Connective tissue which is firm, gives shape to eyelid

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40
Q

Two types of glands present in eyelid and where they are

A

Meibomian glands - tarsal plate

Glands associated with lash follicle

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41
Q

What do meibomian glands secrete and why?

A

Lipid layer of tear film - prevents tear evaporation and spillage over lid

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42
Q

What type of gland is the meibomian gland?

A

Modified sebaceous

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43
Q

what type are they and what do the glands associated with lash follicles secrete?

A

Sebaceous - oily substance

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44
Q

What happens when either of these glands (Meibomian or glands associated with lashes) in the lids gets blocked?

A

Lump in eyelid

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45
Q

Stye vs Meibomian cyst

A

Stye:
Outer part of lid (superficial, blockage of eyelash follicle)
Painful
Red with white punctum (dot)
Infective cause - staphylococcus
Treat with warm compress +/- oral abx

Meibomian cyst:
Deeper within lid (tarsal plate)
Painless
Firm lump palpable and enlarges gradually
1/3 resolve spontaneously, surgical incision if persists

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46
Q

What glands are involved in stye?

A

Blockage of glands of Zeis

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47
Q

What is Blepharitis?

A

Inflammation at the base of the eye lid margin (base lashes)

48
Q

Cause of blepharitis

A

Multifactorial - staphylococcus, meibomian gland dysfunction

49
Q

Signs/symptoms of blepharitis

A

Crusting, Dry eye lids +/- swollen and red

50
Q

Treatment for blepharitis

A

Not serious - warm compress and eyelid hygiene (clean along margin)

51
Q

What is the orbital septum?

A

Thin fibrous sheet originating from orbital rim extending up and down to tarsal plates

52
Q

Function of orbital septum

A

Seperates intra-orbital contents from muscle and subcutanous tissue - barrier for infection spreading from superficial eye (pre-septal) to orbital cavity proper (post-septal)

53
Q

What is the orbital septum continuous with?

A

Tarsal plate

54
Q

Is orbital septum and tarsal plate superficial or deep to orbicularis oculi?

A

Orbital septum and tarsal plate are deep

Orbicularis oculi is superifical

55
Q

What is pre-septal periorbital cellulitis?

A

Infection involving superficial tissues and skin of eyelid (anterior to septum)

56
Q

What is post-septal cellultis?

A

Infection involving tissues WITHIN orbit -posterior or deep orbital septum

57
Q

What is usually the cause of periorbital (pre-septal) cellulitis?

A

Superficial infections from bites/wounds around eye

58
Q

Area affected in pre-septal cellulitis

A

Just the tissues SUPERFICIAL to the orbital septum (and tarsal plates)

59
Q

Symptoms of pre-septal cellulitis

A

Painful, red, swollen lid
Eye movements and vision unaffected

60
Q

How to tell between pre-septal and post-septal cellulitis?

A

Difficult to diiferentiate
In post-septal, eye movements and vision can be affected.

If in doubt urgently refer

61
Q

Usual cause of post-septal cellulitis

A

Spread of infection from paranasal air sinus (maxillary, ethmoid etc)

62
Q

Signs/symptoms of post-septal cellulitis (orbital cellulitis)

A

Proptosis/exopthalmous - protrusion of eyeball
Reduced +/- painful eye movements
Reduced visual acuity

63
Q

Problem with orbital cellulitis

A

Orbital veins drain to cavernous sinus –> can spread intracranially

Cause cavernous sinus thrombosis
Meningitis
Damage to optic nerve - blindness?

64
Q

Contents of the orbital cavity

A

Nerves (II, III, IV, Va, VI)
Blood vessels (ophthalmic artery and vein)
Fat +++
Lacrimal apparatus
Eyeball (globe)
Extra-ocular muscles q

65
Q

What is tear film and lacrimal apparatus?

A

Structures involved in tear production and drainage

66
Q

3 layers of tear film

A

Oily
Water
Mucus

67
Q

What produces what for tear film?

A

Meibomian - oily
Lacrimal - water
Goblet cells in conjuctiva - mucous

68
Q

Where are the lacrimal glands?

A

Supero-lateral eyeball

69
Q

Blinking function for tear flm

A

Distributes film across surface of eye - rinsing and lubricating conjunctivae and cornea

70
Q

What is the lacrimal apparatus for?

A

Collect and drain tear fluid

71
Q

What does obstruction to drainage (lacrimal apparatus) cause?

A

Epiphora (overflow of tears over lower eyelid)

72
Q

Structure order of tear production and drainage

A

Lacrimal glands - produce

Drain to:
Lacrimal punctum
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct
Inferior meatus of nasal cavity

Pools can sometimes nearly drown infants

73
Q

How can nasolacrimal duct be obstructed?

A

Infection
Injury
Stenosis

74
Q

What is the hole in your inner eye draining tears called?

A

Lacrimal punctum

75
Q

What is the eyeball position maintained by?

A

Suspensory ligament (sits under like sling)
Extra-ocular muscles
Orbital fat

76
Q

What is the outer surface of the eyeball covered with?

A

Transparent mucous membrane - conjunctival membrane, reflects onto inner surface of lids

77
Q

What part is not covered by conjuctivae?

A

Cornea - does not extend past limbus (junction between sclera and cornea)

78
Q

What does the conjunctival membrane contain?

A

Blood vessels - vascular

79
Q

Two pathologies affective conjunctivae causing acute red eye

A

Conjunctivitis

Sub-conjunctival haemorrhage

80
Q

Conjunctivitis described

A

Red eye
Uncomfortable, gritty
Watery +/- discharge
Infectious cause - viral (adenovirus)
CONTAGIOUS
Self limiting, will resolve

81
Q

Sub-conjuctival haemorrhage described

A

Burst blood vessel in conjunctiva - very red eye
Painless
No other symptoms
Often no cause - spontaneous
Reassure pt will resolve itself

82
Q

Three layers of the eye:

A

Outer - Sclera (continuous as cornea anteriorly)

Middle - Choroid (vascular) - continues with ciliary body and iris (uveal tract, pigmented)

Inner - Retina - photosensitive layer

83
Q

Region at the back of the eye with indentation

A

Macula - point of highest acuity vision, thinnest part of retinal layer with lots of cones - for CENTRAL vision

Indent is fovea

84
Q

What attaches ciliary body to lens?

A

Suspensory ligaments

85
Q

What does macula appear as when using fundoscope?

A

Red dot
(optic disc is pale disc, start of optic nerve)

86
Q

Blood supply to retina

A

Central - central retinal artery
Outer - blood vessels withion underlying choroid

87
Q

Layers of back of eye

A

Rods and cones closest to choroid (deepest)

Retinal ganglion cells - eventually merging together to form optic nerve

88
Q

What happens when you get an occlusion of the central retinal artery?

A

Sudden painless loss of sight developing over seconds

Usually due to embolus

89
Q

Sign of CRAO on fundoscope

A

Paler retina - ischaemia

Cherry red spot - macula is still getting blood supply by choroid layer but rest of retina is ischaemic so contrasts massively

90
Q

What is the globe of the eye filled with?

A

Aqueous humour (watery)
Vitreous humour (jelly, fills rest of eye)

91
Q

What part does aqueous humour fill?

A

anterior chamber - between cornea and iris
Posterior chamber - between irus and lens/ciliary body

92
Q

What does ciliary body contain?

A

Ciliary muscle
Ciliary process - produces aqueous humour

93
Q

Flow of aqeuous humour

A

Posterior chamber
Through pupil
To anterior chamber -
Nourishes lens and cornea as these have no BV as are transparent

94
Q

Where does aqeuous humour drain?

A

Via iridocorneal angle - between iris and cornea

95
Q

What does aqueous humour drain via after through iridocorneal angle?

A

Via trabecular meshwork and into canal of schlemm –> venous circulation

96
Q

what is glaucoma?

A

Optic nerve damage due to raised intraocular pressure

97
Q

Cause of glaucoma

A

Drainage of aqueous humour from anterior chamber is blocked causing rise in intraocular pressure

98
Q

Chronic glaucoma

A

Open angle glaucoma - most common

Caused by trabecular meshwork deterioration (deteriorates with age so slower onset) ANGLE is FINE

99
Q

Symptoms of chronic open angle glaucoma

A

Asymptomatic - picked up on routine eye tests

100
Q

Progression of chronic glaucoma

A

Increase IOP = optic disc cupping
Gradual loss of peripheral vision

101
Q

Acute glaucoma

A

Closed angle glaucoma (less common)
Narrowed iridocorneal angle is problem
OPHTHALMIC EMERGENCY
–> sight threatening

102
Q

Glaucoma on fundoscopy

A

Glaucomatous cupping of optic disc - increased size of lighter patch on optic disc

103
Q

Presentation of acute angle closure glaucoma

A

Older pt - 55+
Acute painful red eye
Irregular oval pupil (fixed)
Blurred vision
Halo’s around lights
Nausea/vomitting

104
Q

Treatment for acute angle closure glaucoma

A

Drugs to reduce IOP then surgery

105
Q

What must happen to light for us to see?

A

Must reach and be focused onto macula

106
Q

How do we ensure light reaches macula?

A

Transparent lens+cornea

Pupil - regulates light entre

Tear film/cornea - refracts light to bring into focus (bends)

Shape of eyeball - too long (short sighted, myopic) too short (long sighted, hypermetropic)

107
Q

What is the accomodation relfex?

A

To see close objects, this requires a greater refraction of light - beyond cornea capability

(light is very spread out across eye, needs focussing)

108
Q

What happens in the accomodaation reflex?

A

Pupil constricts - limits light coming in

Eyes converge - ensure image remains focused at same point on back of retina

Lens becomes more biconvex (fatter) by contracting ciliary muscle

109
Q

Problem with lens as we age

A

Gets stiffer as we get older, more difficult to see close up objects as eye cannot accomodate - people hold things far away to see them

110
Q

What is age related inability to focus on near objects?

A

Presbyopia

111
Q

What refracts the most light?

A

Tear lined cornea

112
Q

What is phototransduction?

A

Photoreceptors convert light signals (photons) into action potentials

113
Q

Two types of photoreceptors

A

Cones
Rods

114
Q

What do cones do?

A

Colour vision
High definition
Active at high light levels
LOTS at macula and fovea

115
Q

What do rods do?

A

Non-colour vision
Low acuity
Active at low light levels
LOTS at peripheral retina

116
Q

Where do the action potentials go after cones/rods?

A

Propagated via retinal ganglion cells
These collect in area of optic disc forming optic nerve
Then along visual pathway to occipital lobe

117
Q

What is the blind spot?

A

There are no photoreceptors where optic disc is as this is where retinal ganglia collect - blind

Head and Neck (26 decks)

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