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Head And Neck > Anatomy Of Orbit and Eye > Flashcards

Anatomy Of Orbit and Eye Flashcards

1
Q

What is the Orbital cavity?

How many walls does it have?

A

A pyramid shaped bony cavity with the apex pointing posteriorly

4 walls (Superior/ Roof, Inferior/ Floor, Medial and Lateral)

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2
Q

Which walls of the Orbit are the weakest?
Of these 2 bones which one most often fractures?
What does direct impact to front of eye result in?

A
  • Inferior/ Floor and Medial Walls
  • Inferior Wall/ Floor
  • Sudden increase in intraorbital pressure
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3
Q

What do you call a fracture of Inferior/ Medial wall of the Orbit?

A

An orbital blow-out fracture

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4
Q

What bone forms the Medial wall of the orbit?

What do we call the part of this bone in particular that forms the medial wall?

A
  • Ethmoid

- Lamina Papyracea

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5
Q

Despite the Medial Wall of the Orbit being thinner than the Inferior Wall, why does the inferior wall more often fracture upon impact?

A

Walled air cells (Ethmoid air sinuses) in the Medial Wall add extra strength to the wall

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6
Q

The Walled Air Cells of the Medial Wall of the Orbit can become infected (Acute Sinusitis).

What can this lead to, given their proximity to the orbit?

A
  • Infection can break through the thin Lamina Papyracea and track into the orbit OR into cranial cavity
  • Causing Orbital Cellulitis
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7
Q

List the 3 holes of the Orbit and state what structures pass through each

A

Optic Canal;

  • Optic nerve
  • Ophthalmic artery

Superior Orbital Fissure;

  • CN III, IV and VI
  • CN Va
  • Superior Opthalmic Vein

Inferior Orbital Fissure;

  • Inferior Opthalmic Vein
  • Infraorbital nerve
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8
Q

How might a fracture of the Floor of the Orbit affect eye movement?

A
  • Fracture site can ‘trap’ structures (such as Extra-ocular muscles) located near orbital floor
  • Prevents upwards gaze on affected side
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9
Q

List the layers of the eyeball from superficial to deep

A
  • Sclera
  • Choroid
  • Retina
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10
Q

Describe the Sclera in 4 ways

A
  • Fibrous and continuous anteriorly as the Cornea (transparent)
  • Provides attachment for the extra-ocular muscles
  • Gives shape to eyeball
  • Continuous with Dural sheath covering the Optic Nerve at the back of eye
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11
Q

What is the Limbus?

A

Junction between Sclera and Cornea

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12
Q

What happens to the blood vessels running in the Conjunctivae when it becomes inflamed? (Conjunctivitis)

What do patients with Viral Conjunctivitis often report?

A
  • Vessels dilate and eye appears red

- Eye feels uncomfortable and Gritty (as opposed to painful), with tearing of the eye (watery eyes)

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13
Q

Conjunctivitis is highly contagious and can spread very easily.

How do we generally treat?

A
  • Reassurance
  • Hygiene advice
  • Topical chloramphenicol eye drops
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14
Q

Suggest a cause of Conjunctivitis in the neonatal period and a treatment

A

Chlamydial conjunctivitis picked up from mother’s vaginal mucosa

Systemic antibiotics (Erythromycin)

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15
Q

Describe the layer that covers the Sclera

A
  • Thin, transparent cellular layer called the Conjunctivae
  • Extends to edge of the Limbus anteriorly
  • Running posteriorly, reflects onto inner surfaces of eyelids
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16
Q

Other than Conjunctivitis suggest and describe a conjunctival cause of ‘Red Eye’

A

Subconjunctival haemorrhage;

  • Small conjunctival vessels rupture and blood is under conjunctivae
  • Looks worse than it is
  • Common, Painless
  • Only need to reassure that it will slowly resolve
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17
Q

Describe the Middle Layer of the eyeball

A

Choroid;

  • Vascular area
  • Continues anterior as the Ciliary Body and Iris
  • Ciliary body is both Vascular and Muscular (Consists of a Ciliary Process and muscle)
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18
Q

What structure is made up of the Ciliary Body, Iris and Choroid

A

Uvea

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20
Q

How does Uveitis present?

What is it typically associated with?

A
  • Red Eye
  • Painful, worse when focusing/ looking at bright lights

Autoimmune conditions such as;

  • Ankylosing Spondylitis
  • Inflammatory Bowel Disease
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21
Q

What is Iritis?

List 3 ways it presents

A

Anterior uveitis (Inflammation of iris)

  • Painful
  • Red Eye
  • Photosensitivity
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22
Q

Presence of Red Eye with Acute Pain requires urgent referral.

Give an example of such a condition and state 2 possible complications

How may it be treated?

A
  • Uveitis, Inflammation of the Choroid Layer
  • Can lead to Cataracts and Glaucoma
  • Corticosteroids
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23
Q

Briefly describe the inner layer of the eyeball

A

Retina;

  • Photosensitive and Non-photosensitive parts
  • Neurosensory and Pigmented Epithelial Cell layers
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24
Q

Describe the Pigmented Epithelial Cell Layer of the Retina as well as its cells and their function

A
  • PECL lies between Choroid and NSL
  • Its cells contain Melanin which absorbs scattered light that has passed into the eye

This;

  • Reduces reflection, allowing us to focus images appropriately onto the retina
  • Absorbs excess light preventing damage
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25
Q

Very briefly, describe the Neurosensory Layer of the Retina

A
  • Area of retina that senses light

- Where the Photoreceptors (Cones and Rods) are found

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26
Q

Briefly, describe the Cones’ function and state where many of them are concentrated

A
  • Responsible for High Visual Acuity and Colour Vision

- Many are concentrated in the Macula (Centre of your vision)

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27
Q

How does the Macula appear on fundoscopy?

What is the Fovea? What Photoreceptors are found here?

A
  • Slightly darker area of retina, lying just lateral to the Optic Disc

Fovea;

  • Centre of Macula
  • Only Photoreceptors present are Cones
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28
Q

What are the types of Cones?

Name and describe the condition resulting from the absence/ dysfunction of one of these cones

A

Red, Green and Blue-sensitive cones

Colour blindness;

  • Inherited
  • Affects males more frequently than females
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29
Q

How many more Rods are there than Cones?

What do they do?

Where are they more abundant?

A
  • 20 times
  • Responsible for vision in Low Intensity Light (Do not discern colours)
  • Peripheral parts of retina
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30
Q

How do the Rods work?

A

Light energy converted into electrical impulses, which reach Optic Disc

Impulses move along visual pathway to Occipital Lobe

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31
Q

Describe the Optic Disc

A
  • Represents accumulation of Retinal Axons leaving as Optic Nerve
  • Devoid of Photoreceptors, thus called the ‘Blind Spot’
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32
Q

Name 2 structures involved in protecting the surface of the eye

A
  • Eyelids
  • Lacrimal Glands

(Protect from drying out or being injured)

33
Q

By what structures are the eyelids strengthened and given their shape?

What glands do these structures contain?

A

Tarsal Plates, contain Tarsal/ Meibomian Glands

34
Q

State the functions of the oily secretions of the Tarsal/ Meibomian Glands

A

Lubricate edge of eyelid and mix with tear film, preventing tears from evaporating too quickly

35
Q

What can develop if a Tarsal/ Meibomian gland becomes blocked?

How does this present?

A
  • Meibomian Cyst/ Chalazian

- Presents as a lump within the eyelid

36
Q

A Stye can also cause an eyelid lump

How does this present? How is it caused?

A
  • Painful

- Caused by an infected/ blocked Eyelash Follicle OR Sebaceous Gland

37
Q

Blepharitis can also cause an eyelid lump.

What is Blepharitis?

A

Inflammation of eyelids (Including skin, lashes and Meibomian glands)

38
Q

What is the Orbital Septum?

A

Thin sheet of fibrous tissue that fills the base of the orbital cavity

  • Blends with Orbital Rim Periosteum and Tarsal Plates
39
Q

Describe the function of the Orbital Septum and Tarsal Plates

A

Separate Subcutaneous tissue of Eyelid and Orbicularis Oculi from Intra-orbital contents

40
Q

What is Peri-orbital/ Pre-septal Cellulitis?

State 3 features

A
  • Infection occurring within eyelid tissue
  • Superfical to Orbital Septum
  • More common children
  • Ocular function unaffected
  • Can be difficult to differentiate between Peri-orbital and more severe orbital cellulitis
41
Q

How would you treat Pre-Septal/ Peri-Orbital Cellulitis?

A

IV Antibiotics and Surgical Drainage

42
Q

What is Orbital/ Post-Septal Cellulitis?

Suggest 2 causes

A

Infection within the orbit, deep to the Orbital Septum

  • Infection spread from Paranasal air sinuses
  • Pre-Septal infection spread
43
Q

How does Orbital/ Post-Septal Cellulitis present?

A
  • Proptosis/ Exopthalamos
  • Reduced eye movements, may be painful
  • Reduced Visual Acuity
44
Q

The Lacrimal Apparatus refers to the structures involved in tear film production and drainage.

List these structures

A
  • Lacrimal gland (Secretes tears/ Lacrimal fluid)
  • Lacrimal ducts
  • Lacrimal Canaliculi
45
Q

What are the 3 components of Tear Film?

Which glands secrete each component?

A
  • Outer Oily layer, from Meibomian gland
  • Middle Water layer, from Lacrimal gland
  • Inner Mucus layer, from Goblet cells in Conjunctiva
46
Q

Describe the movement of Lacrimal Fluid after release fro Lacrimal Gland

A
  • Enters conjunctival sac through Lacrimal Ducts
  • Passes into Lacrimal lake at medial angle of eye
  • Drains into Lacrimal Sac, then through the Nasolacrimal Duct into the Nasal cavity
47
Q

What can obstruction to Lacrimal Drainage result in?

A

Epiphora (Overflow of tears over lower eyelid)

48
Q

What can result from dirt/particles damaging the cornea?

Why does the Cornea easily regenerate if damaged?

A
  • Corneal abrasions and ulceration (very painful)
  • Outer epithelial layer is constantly undergoing mitosis (Injuries beyond epithelial layer can lead to permanent scarring and visual impairment)
49
Q

What are the 3 chambers of the eye?

What are they filled with

A

Anterior and Posterior;
- Both filled with transparent Aqueous Humour

Vitreous;
- Filled with transparent Vitreous Humour

50
Q

Describe the Anterior Chamber and state how it communicates with the Posterior chamber

A
  • Space between Cornea and Iris

- Communicates with posterior chamber through the pupil (The aperture in the Iris)

51
Q

Describe the Posterior Chamber and its contents

A
  • Space between Iris and Lens
  • Contains Ciliary Body and Processes (in body)
  • Ciliary Processes secrete Aqueous Humour which fills Anterior and Posterior chambers
52
Q

What are 2 functions of the Aqueous Humour?

A
  • Support shape of eyeball

- Provides nourishment to Lens and Cornea (don’t have their own blood supply, are avascular)

53
Q

Describe drainage of the Aqueous Humour

A
  • Drains through Irido-Corneal angle in Anterior Chamber
  • Into Canal of Schlemm, via Trabecular Meshwork
  • Eventually enters Venous Circulation
54
Q

Describe the Blood Supply to the Eye

A

Branches of Ophthalmic Artery supply eye structures

Retina supplied by;

  • Central Retinal Artery
  • Underlying Choroid layer
  • Ciliary arteries (posterior and anterior) feed extensive capillary bed in Choroid Layer
55
Q

Name 4 branches of the Ophthalmic Artery

A
  • Supratrochlear artery
  • Supraorbital artery
  • Central Retinal artery
  • Ciliary arteries
56
Q

What are 2 ways the Retina appears in Central Retinal Artery Occlusion

Why is Choroid still perfused?

A
  • Pale due to Ischaemia
  • ‘Cherry red spot’ represents Macula

Choroid supplied by Ciliary arteries

57
Q

Suggest 3 structures that lose supply when the Ciliary arteries are occluded

A
  • Choroid
  • Optic nerve
  • Deep layer of Retina (Including photoreceptors)
58
Q

Describe the Iris in 3 ways

A
  • Thin, contractile diaphragm
  • Gives colour to eye
  • Consists of 2 muscles, Sphincter and Dilator Pupillae
59
Q

Describe the Lens

A
  • Transparent, Biconvex, Enclosed in a capsule
  • Aneural and Avascular, only receives nutrients from Aqueous Humour
  • Edges of Lens Capsule attached to Ciliary Body by Suspensory Ligaments
60
Q

As we age, proteins in the lens degrade causing it to become Clouded and less transparent.

What is this called? How can it be treated?

A

Cataracts, can be treated with surgery

Occur gradually and cause significant visual impairment

61
Q

How is your sight affected if your eyeball is too;

  • Long
  • Short
A

Too long;
- Short sightedness (Myopic)

Too short;
- Long sightedness (Hypermetropic)

62
Q

At rest describe the;

  • Ciliary muscle
  • Suspensory ligaments
  • Lens
A

CM: Relaxed
SL: Taut
Lens: Relatively flat

63
Q

How does the Lens change to focus on nearer objects?

A

Becomes fatter/ more biconvex (rounder)

64
Q

List the structures of the eye that acts to refract light to focus it onto the retina.

Of these, which is the main refractor?

A
  • Cornea (Main one)
  • Conjunctiva
  • Tear Film
  • Aqueous and Vitreous Humour
65
Q

In what 3 ways does the eye increase its refractive power when looking at very near objects?

A

Via the Accommodation Reflex;

  • Pupil Constriction (less light comes through)
  • Eye Convergence (ensures that both retina are focused on same object at one time)
  • Lens thickening (via Ciliary muscle contraction)
66
Q

Why does the Accommodation Reflex weaken with age?

What is this called?

A

Lens becomes stiffer and less able to change shape

Presbyopia (Age related inability to focus on near object)

67
Q

Describe how the Lens changes in the Accommodation Reflex

A
  • Ciliary muscle contracts, reducing tension of Suspensory Ligaments
  • Elasticity of Lens causes it to become more Biconvex/ fatter
68
Q

What 3 key anatomical structures maintain the eyeball’s position?

A
  • Suspensory ligaments (Sits underneath like a sling)
  • Extra ocular muscles
  • Orbital fat
69
Q

What is Astigmatism?

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

A

Irregularity of Corneal surface

Age related Macular degeneration

70
Q

With age, aqueous humour drainage can get obstructed leading to raised Intra-ocular pressure (IOP).

What can this lead to if untreated?

A

Glaucoma (Irreversible damage and death of Optic nerve) causing visual impairment or even blindness

71
Q

What is the most common type of Glaucoma?

What causes it?

A

Open-angle Glaucoma, caused by blockage within the Trabecular Meshwork (drains aqueous humour into Canal of Schlemm)

72
Q

List 2 signs of Open-Angle Glaucoma

It develops painlessly, initially asymptomatic

A
  • Optic disc cupping

- Gradual loss of Peripheral Vision

73
Q

How can Open-Angle Glaucoma be treated?

A

Topical medications that reduce AH production and/ or increase its drainage, reducing IOP

Surgery may be needed

74
Q

What is Closed-Angle Glaucoma caused by?

(This is an emergency, as permanent sight loss can occur in a few hours)

How does it present?

A

Narrowing of the Irido-Corneal Angle-> Rapid rise in IOP

  • Sudden onset painful, red eye
  • Blurred vision/ Halos around lights (due to corneal oedema)
  • Semi-dilated, Irregular, Oval-shaped pupil
  • Nausea and Vomiting
  • Eye fees Hard and Tender to palpate through upper eyelid
75
Q

How is Closed-Angle Glaucoma treated?

A
  • Diuretics
  • Muscarinic eye drops (cause pupil constriction, opening IC Angle)
  • Analgesia

Surgery: Making a hole in the Iris (Iridotomy)

76
Q

What is Papillary Oedema?

A

Swelling of the optic nerve as it enters the back of the eye due to raised intracranial pressure

Head And Neck (20 decks)

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