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MD4001 - Physiology > The eye and vision; visual pathways > Flashcards

The eye and vision; visual pathways Flashcards

1
Q

What are the three parts of the visual system?

A
  • Eyeball - optical front end and retina/optic disk at the back
  • Connections - optic nerve, optic chiasm, optic tract, LGM, optic radiations
  • Brain - occipital, temporal, frontal and parietal lobes
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2
Q

What is the most common refractive error?

A

Presbyopia

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3
Q

Define presbyopia

A

gradual loss of your eyes ability to focus on near by objects

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4
Q

Define myopia

A

can see objects near to your clearly, but objects further away are blurry

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5
Q

What is the lens correction for myopia?

A

CONCAVE (minus) lenses

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6
Q

Define hypermetropia

A

nearby ojects are blurred, but vision is clearer when looking at objects further away

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7
Q

What is the lens correction for hypermteropia?

A

convex lens

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8
Q

What is the retina?

A

layer at the back of the eye that contains cells sensitive to light

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9
Q

What are the two types of cells in the retina?

A

rods and cones

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10
Q

What are the main features of rod cells

A
  • 120 million onretina
  • high convergence to ganglion cells
  • greyscale vision
  • very light sensitive
  • widespread distribution
  • broad spectral senstivity
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11
Q

What are the main features of cone cells?

A
  • 6 trillion in retina
  • lower convergence to ganglion cells
  • colour vision (red, green, blue)
  • 1/30th of sensitivity of rods
  • concentrated in the macula
  • narrow spectral sensitivity
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12
Q

What is the consequence to vision if the right optic nerve was severed?

A

Loss of sight in the right eye only

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13
Q

What is the consequence to vision if there is damage at the optic chiasm

A

bitemporal hemiaponia

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14
Q

What is the consequence to vision if there is temporal lobe damage

A

superior quadrantanopia

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15
Q

What is the consequence to vision if there is damage to the parietal lobe?

A

Inferior quadrantanopia

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16
Q

What is the consequence to vision if there is damage to the right occiptal lobe

A

left hemianopia

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17
Q

Describe the WHAT (ventral) stream

A

running through the temporal lobes; tells you what the thing is

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18
Q

Where is the visual library of the brain?

A

temporal lobes

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19
Q

Describe the where stream of the brain

A

going through the parietal lobes. Appraises the overall visual scene and allows the brain to see one thing amongst many

20
Q

Where is the attention centre of the brain

A

parietal lobes

21
Q

Where is the action based vision centre of the brain

A

frontal lobe

excecutes a plan based on what it has seen

22
Q

What is simultanagnosia and what causes it?

A

diffuclty finding one thing amongst many

bilateral parietal brain damage

23
Q

What is achromatopsia? And what causes it?

A

unable to see in colour

bilateral anterior occipital brain damage

24
Q

Define visual acuity

A

the ability of the vision system to resolve (‘see’) a gap between two points. This is known as spatial resolution

25
Q

What are the two main types of sight impairment?

A
  • Sight impairment (SI)
  • Severe signt impairment (SSI)
26
Q

RAPD –>

A

Relative Afferent Pupillary Defect

A condition in which the pupils respond differently to light stimuli shone in one eye at a time due to unilateral or asymmetrical disease of the retina or optic nerve

27
Q

What are the causes of RAPD?

A
  • Optic neuritis
  • Anterior ischaemic optic neuropathy (AION)
  • Tumour pressing on the optic nerve
  • Glaucoma
28
Q

What is opacity in the eyes?

A

stops light passing through the cornea to the retina and may cause the cornea to appear white/clouded over

29
Q

What is the retinal reflection test?

A

“RED REFLEX”

When light passes through the pupil and is reflected back of the retina to a viewing aperture, creating a red glow

*blue in black people*

30
Q

What can the retinal reflection test identify?

A
  • corneal scar
  • cataract
  • retinoblastoma
31
Q

Leukocoria =

A

“white pupil”

when the pupil is white rather than black

32
Q

What are the key elements to obserbe when examining the optic nerve?

A

Margin, colour and cup

33
Q

What are the causes of a swollen optic disc?

A
  • Pseudo swelling
    • Small discs
    • Calcium deposits ‘drusen’
  • Genuine swelling
  • Optic Neuritis (VA reduced)
  • Raised ICP (VA normal)
    • SOL
    • IIH
    • Hydrocephalus
34
Q

What extra-ocular eye muscle(s) are supplied by:

CN IV

A

Superior oblique

35
Q

What extra-ocular eye muscle(s) are supplied by:

CN III

A
  • inferior rectus
  • inferior oblique
  • superior rectus
  • medial rectus
36
Q

What extra-ocular eye muscle(s) are supplied by:

CN VI

A

Lateral rectus

37
Q

Features of 3rd CNP

A
  • Vertical diplopia
  • Eye is “down and out”
  • Diplopia every where
  • Pupil dilated and ptosis
  • Can be associated with aneurysm – needs urgent brain imaging and angiogram
38
Q

Features of 4th CNP

A
  • Oblique diplopia
  • Head tilt away from side of the lesion
  • Diplopia worse away from the side of the palsy if unilateral (adduction)
  • Common after head injury
  • Bilateral – might be congenital
39
Q

Features of 6th CNP

A
  • Horizontal diplopia
  • Worse in far distance
  • Worse towards the side of the palsy if unilateral
  • Bilateral – concerned that raised intracranial pressure is present
40
Q

What are the main worldwide causes of blindness?

A
  • cataract
  • age related macular degeernation
  • glaucoma
  • tachoma
  • diabetic retinopathy
  • refractive error
41
Q

Action of superior rectus

A

Main movement is elevation. Also contributes to adduction and medial rotation of the eyeball.

42
Q

Action of inferior rectus

A

Main movement is depression. Also contributes to adduction and lateral rotation of the eyeball.

43
Q

Action of medial rectus

A

Adducts the eyeball.

44
Q

Action of lateral rectus

A

Abducts the eyeball.

45
Q

Action of superior oblique

A

Depresses, abducts and medially rotates the eyeball.

46
Q

Action of inferior oblique

A

Elevates, abducts and laterally rotates the eyeball.

MD4001 - Physiology (11 decks)

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