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2.3.1. Head, Neck & Neuroanatomy > Functional Anatomy and Common Disorders of the Eye > Flashcards

Functional Anatomy and Common Disorders of the Eye Flashcards

1
Q

What bones form the walls of the orbit?

A

Roof = frontal, lesser wing of sphenoid

Floor = maxilla, palatine, zygomatic

Medial = ethmoid, sphenoid

Lateral = zygomatic, greater wing of sphenoid

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2
Q

Which bones of the orbit are must vulnerable to orbital injuries

A

Medial wall and floor

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3
Q

Which direction does the apex of the orbit point?

A

posteriorly

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4
Q

Which direction does the base of the orbit point?

A

Anteriorly

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5
Q

Name the 3 openings at the orbit apex and what they transmit

A

Superior orbital fissure = trochlear (CN IV), oculomotor (CN III), abducens (CN VI), superior ophthalmic vein

Inferior orbital fissure = maxillary N (branch of CN V), inferior ophthalmic vein

Optic canal = optic N, ophthalmic artery

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6
Q

What structures are closely related to the orbit?

A

Ethmoid air cells

Maxillary sinus

Anterior cranial fossa

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7
Q

What is an orbital blow out fracture?

A

Sudden increased in intra-orbital pressure = fractures floor

Orbital contents can prolapse to maxillary sinus

Fracture site can trap structures (extra orbital muscle located near floor)

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8
Q

Outline the presenting features of an orbital blow out fracture?

A

Bruising

Eye not moving = anchoring by nipping of the orbital contents

Periorbital swelling = eyelids might be closed

Double vision

Anaesthesia over affected cheek = cutaneous branches of maxillary division of trigeminal N = infra orbital N runs through floor of orbit, out through infraorbital foramen and innervates cheek and lower eye

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9
Q

How does an orbital blow out fracture present on x-ray?

A

Tear drop sign = prolapse of orbit contents to maxillary sinus through orbital floor

Evidence of fluid in axilla = blood accumulation

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10
Q

What is the role of the eyelids?

A

Protect eye when palpebral fissure is closed

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11
Q

What is the contents of the eyelid?

A

Tarsal plates (fibrous skeleton) = tarus superior/inferior

Muscles

Glands at the edges of eyelids

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12
Q

Outline the contents of the orbital cavity

A

Lacrimal apparatus

Nerves

Blood vessels

Orbital fat

Globe of eye, and its internal structures

Extra-ocular muscles = 6 move the eye

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13
Q

What are the tarsal plates of the eye?

A

Provide connective tissue skeleton to the eyelid

Firmness and shape

Contain tarsal glands

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14
Q

Describe the orbital septum

A

Thin sheet of fibrous tissue

Originating from orbital rim

Blends with tendon of LPS and tarsal plate

Separates intra-orbital contents from eyelid fat and orbicularis oculi muscle

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15
Q

What acts as a barrier against infect spreading from the pre-septal space to post-septal space?

A

Orbital septum

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16
Q

Outline periorbital cellulitis

A

Can be pre-septal (in front of orbital septum) OR post-septal (behind orbital septum)

Cellulitis of orbital structures

Secondary to = infection from bites, periorbital trauma, sinuses

Complications = abscess, spread of infect intracranially (= cavernous sinus thrombosis)

Treat = IV Abx

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17
Q

What enables infection to spread from the orbit, to intracranially?

A

Via venous drainage

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18
Q

Name the glands of the eyelid

A

Meibomian = within tarsal plates, secrete to edge of eyelid

Glands of Zeis = edge of eyelash follicle

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19
Q

Outline the role of glands within the tarsal plate

A

secrete an oily (lipid-rich) substance onto edges of lid = help prevent evaporation of tear film and tear spillage

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20
Q

Describe a meibomian cyst

A

Blockage of meibomain glands within the tarsal plate

No pain, red

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21
Q

Describe a stye

A

Blockage of eyelash follicles – staph infection

Painful, red

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22
Q

What is the lacrimal apparatus?

A

Secretes tears into conjunctival sac

Made up of =

1) Lacrimal gland
2) Lacrimal sac
3) Nasolacrimal duct

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23
Q

Outline the role of blinking

A

washes tear film across front of eye

rinsing and lubricating the conjunctivae and cornea

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24
Q

What is the conjunctiva and its role?

A

Transparent mucous membrane

Produces mucous and tears

Covers sclera and lines inside of eyelids = forming conjunctival sacs

Highly vascular

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25
Q

Describe conjunctivitis (pink eye)

A

Inflamed conjunctiva

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26
Q

Describe subconjunctival haemorrhage

A

Haemorrhage in the conjunctiva

Treat = resolves self

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27
Q

Outline the blood vessels of the orbit

A

Veins = drain to cavernous sinus, pterygoid venous plexus and facial veins

Arteries = ophthalmic A (brach of internal carotid)

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28
Q

Name the nerves of the orbit

A

Ophthalmic Va of trigeminal = general sensory

Optic N = special sensory

Oculomotor, trochlear, abducens = motor Ns

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29
Q

What maintains the position of the eyeball

A

Suspensory lig
Rectus muscle
Orbital fat

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30
Q

Name the structures, out to in, of the eye

A

Cornea = clear

Aqueous humour

Iris = dilate/constrict under autonomic control

Pupil

Lens = inside fibrosis capsule, suspended by ligs attached to ciliary body

Vitreous chamber = vitrous humour

Retina

Macula

Optic disk

Optic N

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31
Q

What is the macula?

A

Near the centre of the retina in the eye,

Region of keenest vision = high conc of cones

Visible on fundoscopy (slightly darker area of retina)

32
Q

What is the optic disc?

A

Raised disc on the retina at the point of entry of the optic nerve

Lacking visual receptors and so creating a blind spot.

33
Q

What is the retina?

A

Inner photosensitive layer = nerve impulses that pass to optic N

Outer pigmented layer lying nearest to choroid

34
Q

What pulls the lens into a flat shape?

A

Ligs and ciliary body muscle

Naturally = fat shape

35
Q

What fills the vitreous chamber?

A

Transparent, jelly-like vitreous humour

36
Q

Where is the anterior chamber of the eye?

A

Aqueous humor-filled space

Between cornea and iris

Communicates with posterior chamber via the pupil

37
Q

Where is the posterior chamber of the eye?

A

Aqueous humor-filled space

Between iris and suspensory lig of lens/ciliary processes

38
Q

How is aqueous humour of the eye produced?

A

Ciliary processes within ciliary body

Flows from posterior chamber, through pupil into anterior chamber

39
Q

What is the role of aqueous humour?

A

Nourishment of the lens which is avascular

40
Q

How is aqueous humour of the eye drained?

A

Iridocorneal angle = between iris and cornea

Into the canal of Schlemm via trabecular meshwork

41
Q

What is glaucoma?

A

Narrowed iridocorneal angle = build up of aqueous humour = rise in intra-ocular pressure = press on optic N

Open-angle glaucoma = blockage within trabecular meshwork

42
Q

How does the photosensitive layer of the retina generate action potentials in response to light?

A

Refraction = light (photons) reaches retina = detected by rods/cons = AP generated = pass ganglion of optic disk = optic nerve

43
Q

Outline refraction in the eye

A

Bending of light by the cornea

Through the vitreous humour

To the retina

44
Q

How is light refracted when focusing on near objects?

A

Light from near-objects – more divergent = requires more refraction

Accommodation reflex =

1) pupil constricts
2) eyes converge = image brought to focus on same point of retina in both eyes
3) lens becomes fatter by suspensory ligs from ciliary body releasing

45
Q

How does age effects the lens?

A

Lens becomes stiffer = cant become fatter= cant focus = keep objects at arms length

Presbyopia

46
Q

Outline cataracts

A

Effects lens = protein deposits in the lens

Light cant pass through lens to retina

47
Q

Name the extrinsic muscles of the eye

A

Inferior oblique (CN III)

Superior oblique (CN IV)

Medial rectus (CN III)

Lateral rectus (CN VI)

Inferior rectus (CN III)

Superior rectus (CN III)

48
Q

Name the intrinsic muscles of the eye

A

Ciliary muscle = changes thickness of lens

Iris = constricts/dilates pupil

49
Q

Which cranial nerves supply the muscles that move the eyeball?

A

CN III
CN IV
CN VI

50
Q

Where do most of the muscles that move the eye originate from?

A

Common tendonas origin – apex of orbital cavity

51
Q

What is the trochlear?

A

Pulley in the eye – superior obliques runs through it, being redirected to attach to the eye laterally

52
Q

Discuss the medial rectus

A

Adducts

Problem = oculomotor N

53
Q

Discuss the lateral rectus

A

Abducts

Problem = abducens N

54
Q

Discus the superior rectus

A

Elevate, medial

= up and in

Test = move eye to lateral position (lateral rectus) then move eyeball up

Problem = oculomotor N

55
Q

Discuss the inferior rectus

A

Depress, medial

= down and in

Tests = move eye to lateral position (lateral rectus) then move eyeball down

Problem = oculomotor N

56
Q

Discuss the superior oblique

A

Depress, lateral, intort

= down and out

Test = move eye into medial position (medial rectus) then move eyeball down

Problem = trochlear N

57
Q

Discuss the inferior oblique

A

Elevate, lateral, extort

= up and out

Test = move eye to medial position (medial rectus) then move eyeball up

Problem = oculomotor N

58
Q

Define intorsion and extorsion

A

Intort = inward rotation

Extort = outward rotation

59
Q

Explain how moving the eyeball to an alternative position and then moving it up or down isolates the testing of an individual muscle?

A

Move eyeball when the direction of gaze is inline with pull of muscle in order to test it

60
Q

What is a cranial nerve palsy?

A

Cranial nerve pathology = complete or partial weakness/paralysis

Causes = congenital, trauma, vascular disease (hypertension, DM, strokes, aneurysms, infect, increased ICP

61
Q

Outline CN III palsy (down and out syndrome)

A

Innervates muscle of eyelid = loss = ptosis

Parasympathetic to sphincter pupillae = loss = dilation

Differential = vasculopathic, tumour, aneurysm

62
Q

Outline CN IV palsy

A

Innervates superior oblique muscle

Lose of normal action = eyeball held extorted, up and in

Compensate by tilting head slightly

Report diff looking down medially (walking down stair, reading)

Differential = vasculopathic, tumour, congenital, trauma

63
Q

Outline CN VI palsy

A

Innervated lateral rectus

Unopposed pull of medial rectus muscle

Unable to Abduct eye on affected side

Diplopia

Differential = vasculopathic, tumour, cranial pressure

64
Q

How is light sensed in the eye?

A

Neurosensory layer of the retina

Cones = high visual acuity and colour vision

Rods = vision in low light, do not discern colours

65
Q

Briefly describe retinal detachment

A

Pigmented layer detaches from neurosensory layer

Can occur spontaneous, or via trauma

Strips photoreceptors of blood supply

66
Q

What types of cones exist?

A

Red
Green
Blue

67
Q

What is colour blindness?

A

Absence/dysfunction of one of the cone types

68
Q

What is the optic disk?

A

Accumulation of retinal axons

No photoreceptors = blind spot

69
Q

What are photoreceptors?

A

Rods and cones

70
Q

Define diplopia

A

Double vision

71
Q

Define presbyopia

A

Hardening of the lens of the eye causing the eye to focus light behind rather than on the retina when looking at close objects

72
Q

What is a papilloedema?

A

Optic disk swelling that is caused by increased intracranial pressure

73
Q

Which structure drains tears from the conjunctival sac directly to the nasal cavity?

A

nasolacrimal duct

74
Q

Which two cranial nerves are involved in the corneal reflex?

A

A reflex response to protect the eye, particularly the cornea, involves first sensing the irritation (via CN Va) which is the afferent (=sensory) arm of this reflex.

The reflex efferent (= motor) response is via the facial nerve, to quickly close our eye (orbicularis oculi).

75
Q

Which two cranial nerves are responsible for pupillary light reflex?

A

CN II Optic = afferent

CN III = efferent

2.3.1. Head, Neck & Neuroanatomy (17 decks)

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