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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
Describe conjunctivitis (pink eye)
Inflamed conjunctiva
26
Describe subconjunctival haemorrhage
Haemorrhage in the conjunctiva Treat = resolves self
27
Outline the blood vessels of the orbit
Veins = drain to cavernous sinus, pterygoid venous plexus and facial veins Arteries = ophthalmic A (brach of internal carotid)
28
Name the nerves of the orbit
Ophthalmic Va of trigeminal = general sensory Optic N = special sensory Oculomotor, trochlear, abducens = motor Ns
29
What maintains the position of the eyeball
Suspensory lig Rectus muscle Orbital fat
30
Name the structures, out to in, of the eye
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
31
What is the macula?
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
What is the optic disc?
Raised disc on the retina at the point of entry of the optic nerve Lacking visual receptors and so creating a blind spot.
33
What is the retina?
Inner photosensitive layer = nerve impulses that pass to optic N Outer pigmented layer lying nearest to choroid
34
What pulls the lens into a flat shape?
Ligs and ciliary body muscle Naturally = fat shape
35
What fills the vitreous chamber?
Transparent, jelly-like vitreous humour
36
Where is the anterior chamber of the eye?
Aqueous humor-filled space Between cornea and iris Communicates with posterior chamber via the pupil
37
Where is the posterior chamber of the eye?
Aqueous humor-filled space Between iris and suspensory lig of lens/ciliary processes
38
How is aqueous humour of the eye produced?
Ciliary processes within ciliary body Flows from posterior chamber, through pupil into anterior chamber
39
What is the role of aqueous humour?
Nourishment of the lens which is avascular
40
How is aqueous humour of the eye drained?
Iridocorneal angle = between iris and cornea Into the canal of Schlemm via trabecular meshwork
41
What is glaucoma?
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
How does the photosensitive layer of the retina generate action potentials in response to light?
Refraction = light (photons) reaches retina = detected by rods/cons = AP generated = pass ganglion of optic disk = optic nerve
43
Outline refraction in the eye
Bending of light by the cornea Through the vitreous humour To the retina
44
How is light refracted when focusing on near objects?
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
How does age effects the lens?
Lens becomes stiffer = cant become fatter= cant focus = keep objects at arms length Presbyopia
46
Outline cataracts
Effects lens = protein deposits in the lens Light cant pass through lens to retina
47
Name the extrinsic muscles of the eye
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
Name the intrinsic muscles of the eye
Ciliary muscle = changes thickness of lens Iris = constricts/dilates pupil
49
Which cranial nerves supply the muscles that move the eyeball?
CN III CN IV CN VI
50
Where do most of the muscles that move the eye originate from?
Common tendonas origin – apex of orbital cavity
51
What is the trochlear?
Pulley in the eye – superior obliques runs through it, being redirected to attach to the eye laterally
52
Discuss the medial rectus
Adducts Problem = oculomotor N
53
Discuss the lateral rectus
Abducts Problem = abducens N
54
Discus the superior rectus
Elevate, medial = up and in Test = move eye to lateral position (lateral rectus) then move eyeball up Problem = oculomotor N
55
Discuss the inferior rectus
Depress, medial = down and in Tests = move eye to lateral position (lateral rectus) then move eyeball down Problem = oculomotor N
56
Discuss the superior oblique
Depress, lateral, intort = down and out Test = move eye into medial position (medial rectus) then move eyeball down Problem = trochlear N
57
Discuss the inferior oblique
Elevate, lateral, extort = up and out Test = move eye to medial position (medial rectus) then move eyeball up Problem = oculomotor N
58
Define intorsion and extorsion
Intort = inward rotation Extort = outward rotation
59
Explain how moving the eyeball to an alternative position and then moving it up or down isolates the testing of an individual muscle?
Move eyeball when the direction of gaze is inline with pull of muscle in order to test it
60
What is a cranial nerve palsy?
Cranial nerve pathology = complete or partial weakness/paralysis Causes = congenital, trauma, vascular disease (hypertension, DM, strokes, aneurysms, infect, increased ICP
61
Outline CN III palsy (down and out syndrome)
Innervates muscle of eyelid = loss = ptosis Parasympathetic to sphincter pupillae = loss = dilation Differential = vasculopathic, tumour, aneurysm
62
Outline CN IV palsy
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
Outline CN VI palsy
Innervated lateral rectus Unopposed pull of medial rectus muscle Unable to Abduct eye on affected side Diplopia Differential = vasculopathic, tumour, cranial pressure
64
How is light sensed in the eye?
Neurosensory layer of the retina Cones = high visual acuity and colour vision Rods = vision in low light, do not discern colours
65
Briefly describe retinal detachment
Pigmented layer detaches from neurosensory layer Can occur spontaneous, or via trauma Strips photoreceptors of blood supply
66
What types of cones exist?
Red Green Blue
67
What is colour blindness?
Absence/dysfunction of one of the cone types
68
What is the optic disk?
Accumulation of retinal axons No photoreceptors = blind spot
69
What are photoreceptors?
Rods and cones
70
Define diplopia
Double vision
71
Define presbyopia
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
What is a papilloedema?
Optic disk swelling that is caused by increased intracranial pressure
73
Which structure drains tears from the conjunctival sac directly to the nasal cavity?
nasolacrimal duct
74
Which two cranial nerves are involved in the corneal reflex?
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
Which two cranial nerves are responsible for pupillary light reflex?
CN II Optic = afferent CN III = efferent

2.3.1. Head, Neck & Neuroanatomy (17 decks)

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