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8 - Eye Flashcards

1
Q

What are the openings into the orbital cavity?

A

Superior orbital fissure
Inferior orbital fissure
Optic canal

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2
Q

What structures are in close proximity to the orbit and why is this dangerous?

A

Paranasal air sinuses - maxillary and ethmoid
Nasal cavity
Anterior cranial fossa
Orbital trauma, fracture through wall could cause damage
Potential spread of infection

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3
Q

What is an orbital blow out fracture?

A

Sudden increase in intra-orbital pressuer from retropulsion of the eyeball, fracturing the floor of the orbit

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4
Q

What are the consequences of an orbital blow out fracture?

A

Orbital contents and blood can prolapse into maxillary sinus
Fracture site can trap extra orbital muscles near floor

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5
Q

What are the symptoms of an orbital blow out fracture?

A

Painful periorbital swelling
Double vision
Impaired vision
Anaesthesia over ipsilateral side as infra-orbital nerve (V2) is damaged

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6
Q

What are the contents of the orbital cavity?

A 
Lacrimal apparatus 
Nerves and blood vessels 
Orbital fat 
Eyeball 
Extrinsic ocular muscles
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7
Q

What is the function of the eyeball and orbital septum?

A

Act as a barrier against infection spreading from pre to post septal space

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8
Q

What constitutes the orbital septum?

A

Fibrous sheet from orbital rim, blends with tendon of levator palpebrae superioris and tarsal plates

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9
Q

What is the function of the tarsal plates?

A

Provide a connective tissue skeleton to the eyelid, giving firmness and shape

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10
Q

What is the function of the orbital septum?

A

Seperates intra-orbital contents from eyelid fat and oribicularis oculi

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11
Q

What causes periorbital cellulitis?

A

Infection from bites, periorbital trauma, fronto-ethmoidal sinus infections

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12
Q

What are the consequences of periorbital cellulitis?

A

Abscess formation and spread of infection intracranially causing cavernous sinus thrombosis

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13
Q

Which type of periorbital cellulitis is most dangerous and why?

A

Post-septal > Pre-septal
Pre-septal is localised
Post-septal, route for infection via veins of orbit to cavernous sinus, pterygoid venous plexus and facial veins

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14
Q

What is a Meibomian cyst?

A

Blockage of the Meibomain glands on the tarsal plate

Non painful

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15
Q

What is the function of the Meibomian glands?

A

Secrete an oily substance onto edges of lid, prevent evaporation of tear film and tear spillage
Keeps eye lubricated

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16
Q

What is a stye?

A

Painful swelling on eyelid caused by eyelash follicles being blocked by staph infection

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17
Q

What is the conjuctivae?

A

Transparent secretory mucosa, covering sclera and inside of eyelids (but not cornea)
Lubricates conjuctival and corneal surfaces with mucous and tears

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18
Q

What constitutes the lacrimal apparatus?

A

Lacrimal glands, arranged around levator palpebrae superioris
Lacrimal sac
Nasolacrimal duct

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19
Q

How is the eye kept lubricated?

A

Blinking, washes tear film across conjunctivae and cornea

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20
Q

What is the difference between conjunctivitis and subconjunctival haemorrhages?

A

Conjuctivitis - inflammation and infection, redness all over eye
Subconjunctival haemorrhage - blood vessel popped in conjuctivae, red in one corner

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21
Q

Describe the blood supply to the eye

A

Arterial: Opthalmic (branch of IC)
Venous: Opthalmic into cavernous sinus, pterygoid plexus and facial vein

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22
Q

What nerve provides general sensation to eye?

A

Opthalmic (V1)

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23
Q

What nerve provides special sensory innervation from retina?

A

Optic (I)

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24
Q

What nerves give motor innervation to muscles of eye?

A

Occulomotor (III)
Trochlear (IV)
Abducens (VI)

25
How is the eyeball kept in position?
Suspensory ligament Rectus muscles Orbital fat
26
What are the layers of the eyeball?
Outer: Sclera and cornea Middle: Choroid, ciliary body and iris Inner: Retina
27
What is the macula?
High cone density area near centre of retina
28
Describe the production and drainage of aqueous humour
Secreted by ciliary processes in ciliary body Flows from posterior chamber, through pupil, into anterior chamber Drains through iridocorneal angle (between iris and cornea) via trabecular meshwork into canal of Schlemm
29
What is the function of aqeuous humour?
To nourish lens and cornea, they have no blood supply or wouldn't be able to see
30
What is glaucoma?
Blockage of aqueous humour drainage causing high intraocular pressure that damages the optic nerve
31
What causes glaucoma?
Chronic: Open angle glaucoma, trabecular meshwork deteriorates Acute: Closed angle glaucoma, narrowing of iridocorneal angle
32
What structures is light refracted through till it reaches the cornea?
``` Air to liquid tear film Through cornea Through lens Through vitreous humour Retina ```
33
How do near objects change the amount of refraction needed to bring them into focus?
Light rays from near-objects are more divergent so require greater refraction to bring into focus
34
How does the eye focus on a near object?
Pupil constricts to prevent too much light entering Eyes converge, so image is brought to focus on same point of retina in both eyes Lens becomes more biconvex (fat)
35
What is presbyopia?
Lens becomes stiffer and less able to change shape with age, so lose ability to focus on near objects
36
What are cataracts?
Progressive opacities that prevent light from passing through to cornea
37
What is a retinal detachment?
Following head trauma, retina (pigmented, epithelial cells) detach from choroid layer where they receive blood supply from, so photoreceptors no longer able to function creating visual disturbances
38
What is the accommodation reflex?
The changes that occur in the lens that allow maintenance of a clear gaze from far to near points
39
What stages of the accommodation reflex are visible?
Automatic contraction of pupil | Convergence of eyes
40
What stages of the accommodation reflex are not visible?
Contraction of ciliary muscle, pulling ciliary body closer to the lens Loosening of suspensory ligaments Lens becomes biconvex
41
How does the eye focus on distant objects?
Ciliary muscles relax, ciliary body further away from lens Tension increases in the suspensory ligaments Lens become biconcave (thinner)
42
How is the eyelid moved?
Orbicularis oculi muscle - Facial (V) - closes eyelid | Levator palpebrae superioris - oculomotor (III) and sympathetics to open eye
43
What are the extrinsic muscles of the eye and how are they innervated?
Muscles of eyelid and muscles that move the eyeball | Innervated by somatic motor and sympathetics
44
What are the intrinsic muscles of the eye and how are they innervated?
Dilator and constrictor of the pupil | Ciliary muscle
45
Which cranial nerves supply muscles that move the eye?
Oculomotor III Trochlear IV Abducens VI
46
Which muscles move the eyes side to side?
Left: Medial rectus Adducts Right: Lateral rectus Abducts
47
Which muscles move the eyes upwards?
Superior rectus moves eyes upwards and medially Inferior oblique moves eye upwards and laterally Eye moves straight up as superior rectus and inferior oblique cancel each other out
48
Which muscles move the eyes downwards?
Inferior rectus moves eyes down and medially Superior oblique moves eyes down and laterally Eyes move straight down as inferior rectus and superior oblique cancel out
49
What are the actions of superior oblique?
Depresses Roll eye out and down (lateral) Intort eye - clockwise roll
50
What are the actions of the inferior oblique?
Elevates Roll eye up and out (lateral) Extort eye - anticlockwise roll
51
What are the actions of superior rectus?
Elevate | Roll eye up and in (medial)
52
What are the actions of inferior rectus?
Depress | Roll eye down and in (medial)
53
How is the function of lateral and medial rectus muscles tested?
Lateral: Abducts (right) Medial: Adducts (left)
54
How are the muscles moving the eye down tested?
Move eye into medial (in) position then move eye down - tests superior oblique Move eye into lateral (out) position - tests inferior rectus
55
How are the muscles moving the eye up tested?
Move eye into medial (in) position then move eye up - inferior oblique Move eye into lateral (out) position then move eye up - Superior rectus
56
What causes cranial nerve palsies?
Intracranial haemorrhage Tumour Vascular disease - diabetes and hypertension
57
Describe the effect of an occulomotor (III) nerve palsy
Eye displaced laterally by lateral rectus and inferiorly by superior oblique as these aren't innervated by CN III, eye is down and out Constriction of pupil as no longer innervates sphincter pupillae via parasympathetics
58
Describe the effect of a trochlear (IV) nerve palsy
Paralysis of superior oblique - eye ball held up and in so difficulty walking downstairs/reading Diplopia
59
Describe the effect of an abducens (VI) nerve palsy
Paralysis of lateral rectus Unopposed pull of medial rectus, eye looking inwards Diplopia

Head and neck (14 decks)

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