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Head neck and neuroanatomy > The eye > Flashcards

The eye Flashcards

1
Q

What bones make up the floor of the orbit?

A

Part of zygomatic bone, maxilla bone

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2
Q

What bones make up the lateral wall of the orbit?

A

the zygomatic bone and the greater wing of the sphenoid bone

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3
Q

What bones make up the roof of the orbit?

A

the frontal bone and a small part of the sphenoid bone

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4
Q

What 4 bones make up the medial wall of the orbit?

A

the maxilla, lacrimal, ethmoid and part of the sphenoid bone

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5
Q

Where are the paranasal sinuses?

A

The ethmoid bone, frontal bone, sphenoid bone and maxilla bone

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6
Q

When do orbital blow out fractures occur and which part of the orbit fractures?

A

Direct trauma to the orbit causing a rise in intraorbital pressure- eg a fist or ball. The floor fractures as this is the weakest part.

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7
Q

This pt got into a fight on a night out. Why can his right eye not look up and has parasthesia over the right cheek

A

he has an orbital blow out frcature. the orbital contents havr porlapsed into the maxillary sinus and inferior oblique muscles and have become trapped.

He cannot feel over the right cheek because CN Vb which runs in the orbital floor has been damaged also.

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8
Q

What is the orbital septum?

A

Fascia that arises from the orbital rim (bone) and bends with the tarsal plates. It seperates intra orbital contents from the eyelid fat and obicularis oris muscle

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9
Q

Which muscles open and close the eyelids and what is their innervation?

A

Open:

  • levator palpebrate superioris: oculomotor nerve
  • Superior tarsal msucle: sympathetics via the end of the oculomotor nerve

Close:

  • orbital part of obicularis oculi: facial nerve
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10
Q

What is the role of the tarsus superior and tarsus inferior?

A

Give the eyelid firmness/ structure and shape

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11
Q

What is wrong with this pt? What may have caused it?

A

Pre- septal orbital cellulitis. This may be due to bites, cuts, stings ect.

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12
Q

What is wrong with this pt?

A

post- septal orbital cellulitis, this is much more severe that pre septal

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13
Q

Give 2 complications of post septal orbital cellulitis

A

Cavernous sinus thombus (spread by inf and sup opthalmic veins)

abcesses

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14
Q

What is this? Which glands is affected?

A

Stye- gland of zies (at base of hair follicle) blocked.

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15
Q

What is this? Which gland is affected?

A

Meibominan cyst- blocked meibomian glands

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16
Q

Which, of stye and meibomian cysts tend to be painful and which is more commonly infected?

A

Stye is more commonly painful and can be infected by staph aureus

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17
Q

How are stye and meibomian cysts tretaed?

A

Hot compression may help speed up recovery, most are self limiting. If they persist you may need to cut them out.

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18
Q

What makes up the lacrimal aparatus?

A

lacrimal glands, lacrimal ducts, lacrimal caniculi

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19
Q

Describe the creation and drainage of lacrimal fluid.

A
  1. lacrimal glands are stimulated by parasymapthetics from the facial nerve to secrete lacrimal fluid
  2. these travel to conjunctiva by lacrimal ducts and they drain across the eye from superiorlateral-> medial, this is aided by blinking
  3. The fluid drains into the superior and lateral punctum and into the lacrimal caniculi
  4. The fluid collects in a lacrimal sac before draining into the nose via the nasolacrimal duct
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20
Q

Describe the consequence of the superior punctum being blocked by a hair?

A

Less drainage of lacrimal fluid= more fluid building up on conjunctiva= weeping/ tears being produced

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21
Q

When can corneal abrasions and ulcers occur?

A

When dust is trapped under the tarsal plates

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22
Q

Why are superficial corneal abrasaions less severe than corneal ulceration to deeper structures?

A

The cornea is always undergoing mitosis so can easily recover, deeper structures dont so cant recover easily, leading to permenant damage

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23
Q

Why can contact lenses no get lost behind the eye?

A

The conjunctiva (thin and transparent layer of cells on top of the sclera) reflects onto the inner surface of the upper and lower eyelids

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24
Q

What type of organism usually causes conjunctivitis? Is it contagious?

A

Usually viral, very contagious.

you also get allergic conjunctivitis

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25
Q

What my pts with conjunctivitis complain of?

A

Concomfortable/ gritty sensation

Tearing

Red eye

Sometimes blurred vision

Itching if allergic cause

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26
Q

How can you differentiate between uveitis and conjunctivitis?

A

Uveitis is painful and made worse by looking at bright lights.

27
Q

What is the pathology shown in the image? How is it managed?

A

Subconjunctival haemorrhage- bleeding from the vessels in the conjunctiva, looks bad but will resolve by themselves

28
Q

What holds the eye ball in the orbit?

A

Lots of orbital fat

Rectus muscles

a suspensory ligament

29
Q

Describe the layers of the eyeball from out to in??

A
  • White sclera, which is continious with the transparent cornea at the front. It is continious with the dural shealth of the optic nerve at the back and provides attachment for muscles.
  • Middle layer is made up of choroid which is continious with the cilary body and iris anteriorly
  • Innermost layer is the retina, there are two layers to the retina; the innermost neural layer and deep to this a pigmented (non photosensitive) layer
30
Q

What causes uveitis?

A

Normally associate with autoimmune disease- causes inflammation of the choroid layer.

It is rare

31
Q

How is uveitis treated?

A

refferal to an opthalmologist for steroids

32
Q

What role does melanine have in the eye?

A

It is produced in the epithelial cells of the retinas innermost pigmented/ non photosensitive layer. It absorbs scattered light, reducing reflection and helping us to focus images on the retina.

33
Q

How are the two types of cells found within the retinas neural layer distributed?

A

Cones are found centrally at the macula, cones more peripherally

34
Q

What is the difference in function of rods and cones?

A

cones detect colour and high definition, rods detect black and white and work well in low light conditions

35
Q

What is the optic disc?

A

A collection of axons bundling together to make the optic nerve, there are no rods and cones here- thus it is our blind spot.

36
Q

Why do you need to wear sunglasses if you have albinism?

A

Because you cant produce melanin so you need sunglasses to absorb the scattered light for you

37
Q

What colours do the 3 types of cones detect?

A

Red, green and blue- deficiency in any of the 3 leads to colour blindness

38
Q

What is retinal detachment and how does it occur?

A

When the two layers of the retina detach. May be due to trauma or spontaneously (almost always in short sited ppl)

39
Q

What is the consequence of retinal detachment?

A

Photoreceptors no longer able to function because they loose their blood supply so you get visual disturbances- blind/black spots/ areas. If not promptly reattached it may lead to retinal detachment.

40
Q

Describe the 3 chambers of the eyeball

A

The vitruous chamber (big one filled w/ vitreous humour (jelly like)

Anterior chamber (between cornea and iris)

Posterior chamber (between lens and iris- communicates with the anterior chamber via the pupil)

41
Q

Describe the normal flow of aqueous humour through the anterior and posterior chambers of the eye ball

A

Aqueous humour produced from cillary body in the posterior chamber flows out posterior chamber through the pupil and into the anterior chamber. Here it flows though the trabecular meshwork at the idiocorneal angle and into the canal of schlemm where its recycled.

42
Q

What is the role of aqueous humour?

A

It supplies the cornea and lens with nutrients as they dont get their own blood supply.

43
Q

What is the difference between open and closed angle glaucoma?

A

Open= blocked drainage at the trabecular meshwork

Closed= acute narrowing of the iridocorneal angle meaning access to the trabecular meshwork is blocked

44
Q

Describe the difference in onset between open and closed onset glaucoma?

A

Closed angle is acute conditon, meaning rapid rise in intraocular pressure

Open angle glaucoma develops over time as the trabecular meshwork gets progressively blocked

45
Q

Describe the difference in presentation between open and closed angle glaucoma?

A

Open angle= painless, slow onset of blurred vision

Closed angle= sudden painful, onset red eye, burred vision, nausia, vomiting, irregular and irresponsive pupil and halos around objects (due to odema)

46
Q

How are open and closed glaucoma managed?

A

Closed: Urgent refferal to opthalmologist to correct the irido- corneal angle as sight will be lost in hours

Open= medicines can be given to reduce aqueous humour production and later surgery if needed. If left untreated it leads to optic nerve damage

47
Q

What nerve controls the thickness of the lens?

A

Autonomics from the oculomotor nerve

48
Q

How is the thickeness of the lens increased to look at nearby objects?

A

Parasympathetic stimulation= contraction of cillary body, this reduces tension on the suspensory ligaments, meaning the lens is able to become fatter and so more refractive

49
Q

Describe the 3 parts to the accomodation reflex?

A

Objects close by to look at=

  1. pupil contracts so less light allowed in
  2. eyes converge (contaction of medial rectus) so both retina loooking in one place
  3. thickening of lens for more refractive power
50
Q

When viewing objects at a normal distance, where does most light refraction take place within the eye?

A

The cornea.

Refraction also occurs as the light goes from air-> lacrimal fluid and at the lens at through the vitreous humour, but less so

51
Q

What causes cateracts?

A

As we age, proteins denaturing in the lens cause it to become clouded and less transparent- can be treated by surgery

52
Q

What is presbyopia?

A

The lens becoming less elastic as we age, reducing our ability to focus on nearby objects. It can be corrected with glasses.

53
Q

What is the difference between short and long sight?

A

Short sight= can only see objects up close (eye too long (myopia), or cornea too curved) so that image focuses infront of retina

Long site: can only focus on obects far away (old age, lens dysfunction, long eye (myeropia)

54
Q

Which 2 extra ocular muscles of the eye are not innervated by the oculomotor nerve?

A

the lateral rectus muscle = Abduces nerve

The superior oblique muscle= Trochlear nerve

LR6 SO4

55
Q

Describe the individual and combined movements of inferior oblique and superior rectus

A

Inferior oblique moves eye up and out and extorts

Superior rectus moves the eye up and in and intorts

Together theyll move the eye straight up due to their opposing horizontal actions

56
Q

What is intortion and extortion and which muscles do them?

A

Intortion is rotating the eye inwards from the top: Superior oblique and superior rectus

Extorition is rotating the eye outwards from the top: Inferior oblique and inferior rectus

57
Q

How are the oblique muscles tested on eye movement testes?

A

The eye is moved medially, in order to fix the action of the rectus muscles so that vertical movement is done by the obliques only. Superior oblique moves the eyeball down, inferior oblique moves it up

58
Q

What will the result of a oculomotor nerve palsy? (3)

A

Eye down and out- as superior oblique and lateral rectus are the only muscles working

Ptosis as lack of innervation ot the levator palpebrae superioris muscle to open eyelid

Dilated pupil as lost parasympathetics to sphincter pupillae

59
Q

What may cause an occulomotor nerve palsy?

A

raised ICP, vasular disease (eg diabetes, hypertension), tumours, aneuysms, cavernous sinus thrombus

60
Q

What will be the result of a trochlear nerve palsy? (3)

A

Loss of superior oblique=

  • loss of intortion leading to head tilt,
  • eyes held in up and in position
  • difficulty looking down and in (stairs, books)
61
Q

What may cause a trochlear nerve injury?

A

Tumour, trauma, raised ICP, vascular disease, congenital

62
Q

What would be the result of an abducens nerve palsy? (3)

A

loss of lateral rectus=

  • eyeball held in wards
  • unable to move eye laterally
  • diplopia on horizontal gaze
63
Q

Why do ppl with graves get wide eyes and bilateral eyelid retraction?

A

increased expression of noradrenaline receptors on superior tarsal muscle

Head neck and neuroanatomy (10 decks)

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