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The Orbit And The Eye Flashcards

0
Q

What bones form the floor of the orbit?

A

Maxilla, zygomatic and palatine

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1
Q

What bones form the roof of the orbit?

A

Frontal and sphenoid bones

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2
Q

What bones form the medial wall of the orbit?

A

Ethmoid, maxilla, lacrimal

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3
Q

What bones form the lateral wall of the orbit?

A

Zygomatic and sphenoid

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4
Q

What is the ornicularis oculi innervated by?

A

The facial nerve (VII)

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5
Q

What is Levator Palpebrae Superioris innervated by?

A

Oculomotor nerve

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6
Q

Which walls of the orbit are most prone to fracture?

A

Medial and inferior wall

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7
Q

Which sinuses can be affected in medial wall fractures?

A

Ethmoidal and sphenoidal

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8
Q

What sinuses can be affected in inferior wall fractures?

A

Maxillary

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9
Q

What happens in a blow- out fracture?

A

The force of the blow displaces the eyeball backwards, increasing the intraorbital pressure and causing a fracture of the floor of the orbit.
The orbital wall and its contents are displaced
Risk of muscle entrapment, diplopia, infection, enophthalmos and pulsatile exopthalmos

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10
Q

Name the 3 fissures in the orbit

A

Optic canal
Superior orbital fissure
Inferior orbital fissure

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11
Q

What travels through the optic canal?

A

Optic nerve

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12
Q

What travels through the superior orbital fissure?

A

Lateral to medial, the pneumonic is Large French Teenagers Sit Numb In Anticipation Of Sweets

Lacrimal nerve
Frontal nerve
Trochlear nerve (CN IV)
Superior branch of the Oculomotor nerve ( CNIII)
Nasociliary nerve
Inferior branch of Oculomotor nerve (CNIII)
Abducens Nerve (CN VI)
Opthalmic Veins
Sympathetic Nerves
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13
Q

What are the coverings of the optic nerve? What is the clinical significance of this?

A

Pia, arachnoid and dura mater of the meninges

Infections of the orbit can spread, tracking backwards to the brain to cause meningitis

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14
Q

What is the structure of the optic nerve?

A

Exits the orbit via the optic canal
1.2 axons from retinal cells
Central artery and vein

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15
Q

What are the consequences of raised intracranial pressure on the optic nerve?

A

Venous engorgement

Papilloedema - optic disc swelling

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16
Q

Name the 7 muscles that move the eyeball and upper eyelid

A

Superior rectus- look up
Inferior rectus- look down
Medial rectus- adducts pupil
Lateral rectus- abducts pupil
Superior oblique- intorsion, depression (in adducted position)
Inferior oblique- abduction and extorsion/ external rotation
Levator Palpebrae Superioris - lifts upper eyelid

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17
Q

What is the lateral rectus muscle innervated by?

A

CN VI- Abducens

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18
Q

What is the superior oblique muscle innervated by?

A

CN IV- Trochlear nerve

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19
Q

What are the other muscles of the eye innervated by?

A

Oculomotor nerve- CN III

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20
Q

What are the consequences of palsy of CN VI (Abducens nerve)?

A

Paralysis of lateral rectus

Unable to abduct pupil so it’s fully adducted due to unopposed pull of medial rectus

21
Q

What usually caused Abducent nerve palsy?

A

Fractures of the orbit or cavernous sinus

22
Q

What are the consequences of Trochlear nerve (CN IV) palsy?

A

Paralysis of superior oblique

Unable to look down when eye is adducted- ie walking down stairs

23
Q

What is a common cause if Trochlear Nerve (CN IV) palsy?

A

Orbital fractures or stretching of the nerve during its course around the brainstem

24
What are the consequences of Oculomotor Nerve (CN III) palsy?
Paralysis of Levator Palpebrae Superioris, sphincter pupillae, medial, superior and inferior rectus and the inferior oblique Eye moves down and out (lateral rectus and superior oblique) Ptosis of upper eyelid - unopposed action of obicularis oculi Pupil is fully dilated and non reactive- unopposed action of dilator pupillae
25
How is the Oculomotor nerve commonly damaged?
Fractures involving the cavernous sinus or aneurysms
26
What is the blood supply to the eye?
Opthalmic artery- branch of Internal Carotid Artery Central Artery of the Retina- branch of Opthamic Artery End arteries Obstruction (eg by embolus) results in instant and total blindness
27
Describe the venous drainage of the eye
Superior and inferior Opthalmic veins- exit via superior orbital fissure, drains into the cavernous sinus Central vein of the retina- drains into the cavernous sinus, directly or via the Opthalmic veins Way of infection spreading from the eye to the brain
28
What is the consequence of blockage of the central vein of the retina?
Slow, painless loss of vision
29
What is the function of the eyelids?
Protect the cornea and eyeball from injury | Cover the cornea with lacrimal fluid to keep it moist
30
What lines the inner surface of the eyelids?
Conjunctiva
31
Which angle of the eye do dust and foreign materials get swept to to be removed?
Medial angle
32
What strengthens the eyelids?
Tarsal plates- dense connective tissue, contains tarsal glands.
33
What do the Tarsal Glands produce?
Secretions that lubricate the edges of the eyelids and prevent them sticking together when they close
34
Name the 4 components of the lacrimal apparatus
Lacrimal gland Lacrimal ducts Lacrimal canaliculi Nasolacrimal duct
35
What does the lacrimal gland do?
Secretes lacrimal fluid- watery physiological saline Contains bacteriocidal lysozyme enzyme Moistens and lubricates the surfaces of the conjunctiva and cornea Provides nutrients and dissolved oxygen to the cornea
36
Where is the lacrimal gland located?
Lacrimal fossa, superiolateral part of orbit
37
What do the lacrimal ducts do?
Conduct lacrimal fluid from the gland to the conjunctival sac, where lacrimal fluid can drain to the nasal cavity
38
What does the lacrimal canaliculi do?
Commence at the medial angle of the eye where lacrimal fluid is drained from the lacrimal lake to the lacrimal sac
39
What does the nasolacrimal duct do?
Conveys lacrimal fluid to the inferior nasal meatus | Inferior to the inferior nasal concha
40
What muscles open the eyelids?
Levator Palpebrae Superioris (CN III) | Assisted by the superior tarsal muscles- sympathetically innervated, - Horner's syndrome
41
What muscles cause the eyelids to close?
Obicularis Oculi- (CN VII) | - Bell's Palsy
42
What are the consequences of the eyelids being prevented from closing? Eg the paralysis of obicularis oculi in Bell's palsy
Cornea becomes dry and is left unprotected from dust and other particles
43
What is the name of the opening of the eyelids?
Palpebral fissure
44
Name the conjunctival layers of the eye
Palpebral conjunctiva and bulbar conjunctiva
45
From outer to inner, what are the layers of the eyelid?
``` Skin Loose areolar connective tissue Tendons of obicularis oculi Tendons of Levator Palpebrae Superioris Superior tarsus Ciliary gland Palpebrae conjunctiva ```
46
What is Horner's Syndrome?
Absence of sympathetic stimulation on the ipsilateral side of the head due to an interruption of a cervical sympathetic trunk. Miosis- construction of the pupil due to unopposed action of sphincter pupilae, paralysis of dilator pupilae Ptosis- drooping of the superior eyelid due to paralysis of the Superior Tarsal muscle (smooth muscle fibres interdigitated with aponeurosis of Levator Palpebrae Superioris) Vasodilation- due to loss of sympathetic tone. Redness and hot skin Anhydrosis- absence of sweating
47
Name 3 causes of exopthalmos
Grave's Disease (Hyperthyroidism) Aneurysm Haematoma
48
How is the eye affected when intracranial pressure rises?
Optic nerve is surrounded by meninges. The subarachnoid space is surrounded by CSF. An increase in CSF pressure can compress the optic nerve, compressing the blood vessels supplying the retina. The vein is occluded before the artery, leading to oedema of the retina (papillodema)
49
What are some common causes of Red Eye?
Trauma, infection, allergy, increased pressure in the eye, conjunctival haemorrhage (coughing spells or recurrent vomiting)
50
What is a Meibomian Cyst?
Blocked Tarsal Gland, lies behind the eyelash within the eyelid
51
What is a stye?
Infection of the sebaceous gland at the base of the eyelash

Head And Neck (8 decks)

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