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Sem 4 > H&N 6: The Orbit > Flashcards

H&N 6: The Orbit Flashcards

1
Q

What is the inferior border of the orbit?

A

Zygomatic and maxillary bones

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2
Q

What is the superior border of the orbit? (Roof)

A

Sphenoid and frontal bone

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3
Q

What is the medial border of the orbit?

A

Sphenoid, ethmoidal, lacrimal and maxillary bone

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4
Q

What is the lateral border of the orbit?

A

Zygomatic and sphenoid bones

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5
Q

Which border of the orbit is weakest?

A

Inferior, so this part is most likely to fracture

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6
Q

What are the important anatomical markings/ fissures in the sphenoid bone?

A

Optic canal
Superior orbital fissure
Inferior orbital fissure

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7
Q

What comes through the optic canal?

A

Optic nerve and ophthalmic artery

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8
Q

What comes thought the superior orbital fissure?

A

Cranial nerves V1, III, VI and superior ophthalmic vein

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9
Q

What the outer layer of the eyeball made up of?

A

Tough fibrous sclera (5/6th) and transparent cornea (1/6th) anteriorly

Transparent conjunctiva layer covers the sclera (not cornea)and blood vessels run through this layer, if these become inflamed the blood vessels dilate and become -> conjunctivitis

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10
Q

What is the middle layer of the eyeball made up of?

A

Vascular layer made up of choroid, ciliary body and iris

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11
Q

What is the inner layer of the eyelid made up of?

A

The retina, which transmits light energy signals unto nerve impulse to be sent down the optic nerve and to the brain

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12
Q

How can we look into the eye?

A

Via a Fundoscopy, using an ophthalmoscope

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13
Q

How do we know which eye we are looking at when looking at a fundus?

A

Because the optic disc is always on the nasal side

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14
Q

What is the name of the area with the most visual activity that can be seen in a fundus?

A

The fovea

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15
Q

What is a cataract?

A

Loss of transparency of the lens

Tx is cataract extraction with new lens implanted

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16
Q

What the outer layer of the eyeball made up of?

A

Tough fibrous sclera (5/6th) and transparent cornea (1/6th) anteriorly

Transparent conjunctiva layer covers the sclera (not cornea)and blood vessels run through this layer, if these become inflamed the blood vessels dilate and become -> conjunctivitis

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17
Q

What is the middle layer of the eyeball made up of?

A

Vascular layer made up of choroid, ciliary body and iris

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18
Q

What is the inner layer of the eyelid made up of?

A

The retina, which transmits light energy signals unto nerve impulse to be sent down the optic nerve and to the brain

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19
Q

How can we look into the eye?

A

Via a Fundoscopy, using an ophthalmoscope

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20
Q

How do we know which eye we are looking at when looking at a fundus?

A

Because the optic disc is always on the nasal side

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21
Q

What is the name of the area with the most visual activity that can be seen in a fundus?

A

The fovea

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22
Q

What is a cataract?

A

Loss of transparency of the lens

Tx is cataract extraction with new lens implanted

23
Q

How does the humor vary between the different segments of the eye?

A

Anterior segment (made of anterior and posterior chambers) produces aqueous humor which provides nourishment to the lens and cornea which don’t have their own blood supply

Posterior segment produces vitreous humor

Both humors support the shape of the eyeball

24
Q

Where does aqueous humor drain?

A

Into the canal of Schlemm via a trabecular mesh work

25
Q

What is glaucoma?

A

An obstruction to the drainage of aqueous humor which raises intra ocular pressure

If untreated it could irreversible damage the optic nerve and cause visual impairment

26
Q

What is the most common type of glaucoma?

A

Open angle glaucoma

27
Q

What is the difference between open angle and closed angle glaucoma?

A

Open angle is caused by a blockage of the trabeculae mesh work which develops painlessly over time
Tx is eye drops to reduce aqueous humor production/ increase its drainage

Closed angle is when the iris closes the drainage angle, blocking off access to the trabecular mesh work causing a rapid rise in intra ocular pressure
Sudden onset of painful red eye, blurred vision, eye is hard to palpate, halos around objects, medical emergency
Tx is eye drops, analgesics, and drugs to reduce the pressure

28
Q

Which two muscles form the iris and control the size of the pupil?

A

Sphincter and dilator pupillae

29
Q

What are the muscles that control the movement of the eye and what is their innervation?

A

LR6SO4R3

Lateral rectus, CN VI
Superior oblique, CN IV
Remaining muscles (medial rectus, superior rectus, inferior rectus, inferior oblique), CN III

30
Q

What is the function of the superior and inferior oblique muscles?

A

Superior oblique looks down and in

Inferior oblique looks up and inx

31
Q

How do we test the extra ocular muscles?

A

Drawing a H with your finger and asking the patient to follow your finger as it does so

32
Q

What is the blood supply to the eye?

A

The ophthalmic artery, which is a branch of the ICA

The retina is supplied by the central retinal artery, a branch of the ophthalmic artery

33
Q

How would a central retinal artery occlusion present on a Fundoscopy?

A

Cherry red spot on a pale back ground

34
Q

What is the venous drainage of the eye?

A

Into ophthalmic veins which drain into cavernous sinus

35
Q

What muscles can open and close the eyelid and what is their innervation?

A

Orbicularis oculi closes the eyelid, CN VII (muscle of facial expression)

Levator palpebrae superioris opens the eyelid, CN III (oculomotor nerve)

The superior tarsal plates assists in opening the eyelid, and is innervated by the sympathetic nervous system

36
Q

What is the difference between the course of complete ptosis and partial ptosis?

A

Complete ptosis is a CN III lesion (paralysis of levator palpebrae superioris)

Partial ptosis is a sympathetic nerve lesions ie Horners syndrome (paralysis of superior tarsal plate)

37
Q

What is the lacrimal apparatus made up of?

A

Lacrimal gland is in superiolateral part of the orbit and secretes lacrimal fluid
Fluid drains via lacrimal ducts into the lacrimal sac, before passing into the nasolacrimal duct

38
Q

What is the accommodation reflex?

A

Automotive contraction of pupil when focusing on a nearby object, having focused on a distal object (or vice versa)
Lens changes shape via contraction of ciliary muscles

39
Q

How does the accommodation reflex change with age, and how can this be treated?

A

Lens becomes more dense and less elastic with age, so is less able to change shape
Results in impaired ability to focus on nearby objects
Can be corrected with glasses

40
Q

What is a stye?

A

Red tender lump at edge of eyelid

Due to bacterial infection of ciliary glands

41
Q

What is a blowout fracture?

A

Trauma causing fracture to inferior or medial wall of the orbit
Can raise intra orbital pressure -> exophthalmos
Contents can herniate into ethmoidal and maxillary sinuses

42
Q

What is a meibomian cyst?

A

Aka chalazion
Firm lump on eyelid (like a large stye) due to inflammation/ infection of Meibomian gland
Often clear alone, may require surgery

43
Q

What is papilloedema?

A

Swollen optic disc due to increased intracranial pressure

Apparent on Fundoscopy

44
Q

How would a CN IV lesion present?

A

Head tilt away (superior oblique muscle paralysed so eye is slightly up and out so head tilts to reduce this)
Double vision, hard to read and walk down stairs etc (affected eye can’t go down)

45
Q

How would a CN VI lesion present?

A

Eye will appear cross eyed, lateral rectus paralysed so affected eye won’t look outwards

46
Q

How can cranial nerve palsies be caused?

A

Vasculitis
Raised ICP
Tumour compressing nerves

47
Q

What are the afferent and efferent limbs of the pupillary light reflex?

A 
Afferent limb (sensory) is optic nerve
Efferent limb (motor) is oculomotor nerve (parasympathetic fibres)
48
Q

Outline the direct and consensual pupillary light reflex if light was shone into the left eye?

A

Light in left pupil
Sensory afferent form left retina via CN II
To the brainstem (pretectal nucleus)
Connection with Edinger westphal nucleus (left and right)
Parasympathetic fibres from EDW leave brainstem
Hitchhike into CN III
Pass the ciliary ganglion
Reach sphincter pupillae
Left eye = direct, right eye = consensual

49
Q

What is the macula?

A

The centre of the retina, area responsible for most visual activity

50
Q

What produces aqueous humour?

A

The ciliary body, in the posterior chamber (anterior segment) of the eye

51
Q

How is papilloedema different to optic disc cupping?

A

Papilloedema is due to raised intra CRANIAL pressure (Ie pressure from behind the optic nerve, from surrounding meninges)

Optic disc cupping is due to raised intra OCULAR pressure (ie pressure from in front of optic nerve) presents as an increased cup to disc ratio on Fundoscopy but the optic disc does not appear swollen and is still well defined, unlike papilloedema

52
Q

What is presbyopia?

A

As the eye ages, the lens becomes less elastic and less able to change its shape impairing its ability to accommodate to near objects

53
Q

Why dos conjunctivitis not affect the cornea?

A

As the conjunctiva does not over lie the cornea

54
Q

What is the difference between a stye and Meibomian cyst?

A

Stye is blockage of a sebaceous gland situated at the base of the eyelash
Meibomian cyst is blockage of meibomian gland posterior I to the eyelash within the eyelid

Sem 4 (25 decks)

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