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NEUROLOGY AND NEUROSCIENCE 2 > VISUAL SYSTEM > Flashcards

VISUAL SYSTEM Flashcards

1
Q

What is the function of the lacrimal system?

A

Production of tears - basal, reflex and emotional

Drainage of tears

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2
Q

What are the afferent divisions of the lacrimal system?

A 
Cornea
CN V (ophthalmic trigeminal)
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3
Q

What is the efferent supply of the lacrimal system?

A

Parasympathetic

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4
Q

Which neurotransmitter is used in the lacrimal system?

A

acetylcholine

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5
Q

Describe the journey of a tear in the lacrimal system

A
  • Produced by lacrimal gland
  • Drains through the upper/lower punctum
  • Flows through superior/inferior canaliculus
  • Gather in tear sac
  • Exit tear sac through tear duct into nasal cavity
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6
Q

What is the tear film and its functions?

A

Thin fluid layer covering eye

  • Maintains smooth cornea-air surface and supplies
    oxygen to cornea (no blood vessels supply cornea)
  • Removal of debris
  • Bactericide
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7
Q

What are the 3 layers of the tear film and their functions?

A

Superficial lipid layer - reduces tear film evaporation
Aqueous layer
Mucinous layer - maintains surface wetting

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8
Q

What glands produce the superficial lipid layer?

A

Row of Meibomian glands along lid margins

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9
Q

What is the conjunctiva?

A

Thin transparent tissue which covers the outer surface of the eye. Begin at outer edge of cornea, covers visible part of eye and lines the inside of the eyelids

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10
Q

How does the conjunctiva get its blood supply?

A

Nourished by tiny blood vessels that are nearly invisible to the naked eye unless conjunctivitis

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11
Q

What are the 3 layers of the eyeball and label them on a diagram

A

Sclera - hard and opaque - “white of the eye”
Choroid - red and vascular
Retina - neurosensory tissue

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12
Q

What is the function of the sclera?

A

Tough, opaque tissue which serves as the eye’s protective outer coat

As you move to front of eye, the sclera seamlessly changes to the cornea

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13
Q

Name the different layers of the cornea from outer to inner

A 
Epithelium
Bowman's membrane (basal membrane)
Stroma
Descemet's membrane
Endothelium
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14
Q

What is the water content of the sclera?

A

High

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15
Q

What is the water content of the cornea?

A

Low

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16
Q

What is the function of the endothelium of the cornea?

A

Pumps fluid out of cornea and prevents cornea oedema

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17
Q

What is the function of the cornea?

A

Powerful refracting surface - 2/3 of the eye’s focusing power

Gives clear window to look through

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18
Q

What is the uvea and describe its structure?

A

Vascular coat of eyeball and composed of 3 parts:

  • Iris
  • Ciliary body
  • Choroid

Intimately connected so disease of one part also affects the other portions

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19
Q

Where does the uvea lie?

A

Between sclera and retina

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20
Q

What is the function of the choroid?

A

Composed of layers of blood vessels that nourish the back of the eye

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21
Q

What is the function of the iris?

A

Controls light levels inside eye

Embedded with tiny muscles that dilate and constrict the pupil size

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22
Q

Describe the structure of the lens

A

Outer acellular capsule

Regular inner elongated cell fibres - transparency

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23
Q

What is a cataract?

A

When a lens looses its transparency with age

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24
Q

What are the functions of the lens?

A

Transparent
Regular structure
Refractive power - 1/3 of eye focusing power

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25
Q

What is the retina and its function?

A

Thin layer of tissue which lines inner part of posterior eye

Captures light rays and then sends impulses to the brain via optic nerve

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26
Q

What is the name of the area where the optic nerve joins the retina and what does it create?

A

Optic disc

Creates a blind spot since no light sensitive cells there

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27
Q

What is the macula?

A

Small and highly sensitive part of the retina responsible for detailed central vision
Located roughly in centre of retina, temporal to optic nerve

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28
Q

What is the fovea?

A

Centre of the macula

Most sensitive part of retina

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29
Q

What allows the fovea to perceive in detail?

A

Highest concentration of cones

Low concentration of rods

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30
Q

What is central vision assessed by?

A

Visual acuity assessment

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31
Q

What is peripheral vision assessed by?

A

Visual field assessment

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32
Q

What is central vision important for?

A

Detail day vision, colour vision, reading, facial recognition

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33
Q

What is peripheral vision important for?

A

Shape, movement, night vision, navigation vision

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34
Q

What is the structure of the retina?

A

3 layers: outer, middle and inner

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35
Q

What cells are present in the outer layer of the retina and thus its function?

A

Photoreceptors (1st order neurons) allowing detection of light

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36
Q

What cells are present in the middle layer of the retina and thus its function?

A

Bipolar cells (2nd order neurons) providing local signal processing to improve contrast sensitivity and regulate sensitivity

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37
Q

What cells are present in the inner layer of the retina and thus its function?

A

Retinal ganglion cells (3rd order neuron) which transmit the signal from the eye to brain

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38
Q

Describe rod photoreceptors

A

100x more sensitive to light than cones
Have a longer outer segment with photo-sensitive pigment
Slow response to light
Responsible for night vision (scotopic vision)

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39
Q

Describe cone photoreceptors

A

Less sensitive to light
Fast response to light
Responsible for day light fine vision and colour vision (photopic vision)

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40
Q

What are the different types of cones and their functions?

A

S-cones: blue wavelength of light
M-cones: green wavelength of light
L-cones: red wavelength of light

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41
Q

What is the most frequent form of colour blindness?

A

Deuteranomaly AKA Daltonism

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42
Q

What is irregular about patients with deuteranomaly?

A

They don’t perceive the colour red

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43
Q

What is the name for full colour blindness?

A

achromatopsia

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44
Q

What is the equation for the index of refraction

A

Speed of light in vaccuum/speed of light in a medium

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45
Q

What does a convex lens do to light?

A

Converges light rays to a point

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46
Q

What does a concave lens do to light?

A

Diverges light rays, spreading them outwards

Focal point in front of lens

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47
Q

What does emmetropia mean?

A

Adequate correlation between eyeball’s axial length and refractive power meaning object at distance is focused exactly on retina resulting in perfect vision

Parallel light rays fall on retina (no accomodation)

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48
Q

What does ametropia mean?

A

Mismatch between eyeball’s axial length and refractive power.

Parallel light rays don’t fall on retina

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49
Q

What conditions fall under the umbrella of ametropia?

A

Myopia
Hyperopia
Astigmatism
Presbyopia

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50
Q

What occurs in myopia and its causes (2 types)?

A

Parallel rays converge at focal point anterior to retina

Caused by excessive long globe (axial myopia) - more common
Or excessive refractive power (refractive myopia)

51
Q

What are the symptoms of myopia?

A

Blurred distance vision
Squint in an attempt to improve uncorrected visual acuity when gazing into distance
Headache

52
Q

What treatments are there for myopia?

A

Correction with diverging lens
Correction with contact lens
Correction by removing lens to reduce refractive power

53
Q

What occurs in hyperopia and its causes??

A

Parallel rays converge at focal point posterior to retina

Caused by excessive short globe (axial hyperopia) - more common
Or insufficient refractive power (refractive myopia)

54
Q

What are the symptoms of hyperopia?

A

Visual acuity at near tends to blur relatively early
Asthenopic symptoms (eyepain, headache, burning in eyes)
Amblyopia - uncorrected hyperopia > 5D

55
Q

What is the nature of the blur in hyperopia?

A
  • blurred vision is more noticeable if person is tired,
    printing is weak or light inadequate
  • varies from inability to read fine print to near vision is
    clear but suddenly and intermittently blur
56
Q

What treatments are there for hyperopia?

A

Correction with converging lenses
Correction with converging lenses and cataract extraction
Correction with contact lenses
Correction with intraocular lenses

57
Q

What occurs in astigmatism and its causes??

A

Parallel rays come to focus in 2 focal lines/points rather than a single focal point (hereditary)

Caused by a non-spherical refractive media
- refract differently along one meridian than along
meridian perpendicular to it

58
Q

What are the symptoms of astigmatism?

A

Asthenic symptoms (headache, eyepain)
Blurred vision
Distortion of vision
Head tilting and turning

59
Q

What is the treatment for regular astigmatism?

A

Cylinder lenses with or without spherical glasses

60
Q

What are the treatments for irregular astigmatism?

A

Rigid cylinder lenses

Surgery

61
Q

What is the near response triad?

A

Adaptation for near vision:
- Pupillary miosis (sphincter pupillae) to increase depth
of field
- Convergence (medial recti) to align both eyes towards
near object
- Accomodation (circular ciliary muscle) to increase
refractive power of lens for near vision

62
Q

What is presbyopia?

A

Naturally occurring loss of accommodation (focus for near objects)
Distant vision is still intact
Onset from 40+ years old

63
Q

How is presbyopia corrected?

A

Convex lenses in near vision:

  • Reading glasses
  • Bifocal glasses
  • Trifocal glasses
  • Progressive power glasses
  • Contact lenses
64
Q

What are the positives of contact lenses?

A

Higher quality of optical image
Less influence on the size of retinal image than spectacle lenses
Cosmetic
Athletic activities

65
Q

What are the negatives of contact lenses?

A

Careful daily cleaning and disinfection
Expense
Complications e.g. infectious keratitis

66
Q

What are intraocular lenses and what condition are they most used for?

A

Used to replaced cataract crystalline lens
Best optical correction for aphakia (lack of lens) - avoids significant magnification and distortion caused by spectacle lenses

67
Q

Detail the steps of laser surgical correction

A 
Cutting of corneal flap
Flipping of corneal flap
Photorefractive treatment (laser)
Corneal stroma reshaped post laser
Corneal flap put back into position
68
Q

What is the Staar intra-collamer lens (ICL) and when is it used?

A

Lens which is inserted over the natural lens of the eye and underneath the iris to correct myopia and astigmatism

69
Q

What is the problem with the Staar intra-collamer lens (ICL)?

A

Eventually natural lens will become cloudy (cataract) and then you have to remove both lenses

70
Q

How are intraocular lenses (IOL) implanted in patients?

A

First clear lens extraction (same as cataract extraction):
- Use phaco tip which uses ultrasound to break up the
retinal lens and sucks it up

Then implant artificial IOL

71
Q

What do patients with an intraocular lens lose?

A

Accommodation (patient will need reading glasses)

72
Q

At what visual pathway landmark do ganglion nerve fibres synapse?

A

Lateral geniculate nucleus

73
Q

What is the optic radiation?

A

4th order neurone

74
Q

What is the optic tract?

A

Ganglion nerve fibres exit as optic tract

75
Q

List the visual pathway landmarks in order

A 
Optic nerve
Optic chiasm
Optic tract
Lateral geniculate nucleus
Optic radiation
Primary visual cortex
76
Q

Draw a diagram showing the decussation of nerve fibres at the optic chiasm

A

Do it bitch

77
Q

What percentage of ganglion fibres cross at the optic chiasm?

A

53%

78
Q

How do lesions anterior and posterior to the optic chiasm affect the visual fields respectively?

A

Anterior lesion - visual field in one eye only affected

Posterior lesion - visual field in both eyes affected

79
Q

What does a lesion at the optic chiasm cause?

A

Bitemporal hemianopia

80
Q

What does a right sided lesion posterior to the optic chiasm cause?

A

Left homonymous hemianopia in both eyes

81
Q

What does a left sided lesion posterior to the optic chiasm cause?

A

Right homonymous hemianopia in both eyes

82
Q

What is bitemporal hemianopia typically caused by?

A

Enlargement of pituitary gland

83
Q

What is homonymous hemianopia typically caused by?

A

Stroke (cerebrovascular accident)

84
Q

What does a lesion at the primary visual cortex cause?

A

Contralateral homonymous hemianopia with macular sparing

85
Q

Why does macula sparing occur?

A

Area in primary visual cortex that represents the macula gets dual blood supply from the posterior cerebral arteries from both sides

86
Q

What is damage to the primary visual cortex often caused by?

A

Stroke

87
Q

What does pupil constriction do?

A

Increases depth of field
Decreases spherical aberrations and glare
Reduces bleaching of photo-pigments

88
Q

What nerve mediates pupillary constriction?

A

Parasympathetic nerve of CN III

89
Q

Which muscles contract to cause pupil constriction?

A

Circular muscles

90
Q

Which muscles contract to cause pupil dilation?

A

Radial muscles

91
Q

What does pupil dilation do?

A

Increases light sensitivity in dark by allowing more light into eye

92
Q

What nerve mediates pupillary dilation?

A

Sympathetic nerve of CN III

93
Q

Detail the afferent pathway of the pupillary reflex

A
  • Photoreceptors –> bipolar cells –> retinal ganglion cells
  • Decussation at optic chiasm
  • Pupil-specific ganglion cells exit at posterior third of
    optic tract
  • Enter lateral geniculate nucleus
  • Each pathway from each eye synapses on both Edinger-
    Westphal nuclei on both sides in brainstem
94
Q

Detail the efferent pathway of the pupillary reflex

A
  • Edinger-Westphal nucleus –> oculomotor nerve efferent
  • Synapses at ciliary ganglion
  • Short posterior ciliary nerve –> pupillary sphincter
95
Q

Draw out the pupillary reflex pathway with landmarks

A

Afferent:
Photoreceptors —> Bipolar cells —> Retinal ganglion cells —> Pupil specific ganglion cells exit at posterior optic tract —> Lateral geniculate nucleus —> Each eye synapses at Edinger-Westphal nuclei on both sides of brain stem

Efferent:
Edinger-Westphal nuclei —> oculomotor nerve —> synapse at ciliary ganglion —> short posterior ciliary nerve —> pupillary sphincter

96
Q

What is the difference between direct and consensual pupillary light reflex?

A

Direct: constriction of pupil of the light stimulated eye
Consensual: constriction of pupil on the other eye

97
Q

What is the neurological basis behind the consensual pupillary light reflex?

A

Afferent pathway on either side alone will stimulate efferent pathway on both sides

98
Q

What happens when there is a right afferent defect to the optic nerve?

A

No pupil constriction in both eyes when right eye is stimulated with light

Normal consensual pupil constriction in both eyes when left eye is stimulated with light

99
Q

What happens when there is a right efferent defect to CN III (oculomotor)?

A

No right pupil constriction whether right or left eye is stimulated with light

Left pupil constricts whether right or left eye is stimulated with light

100
Q

How do you test for afferent pupillary defect?

A

Swinging torch test - alternating stimulation of right and left eye with lightt

101
Q

How do you test for RAPD and what do you expect to see?

A

Swinging torch test

Partial pupillary response still present when damaged eye is stimulated

  • Both pupils CONSTRICT when light swings to undamaged side
  • Both pupils paradoxically DILATE when light swings to the damaged side
102
Q

What does duction mean?

A

Eye movement in one eye

103
Q

What does version mean?

A

Simultaneous movement of both eyes in the same direction

104
Q

What does vergence mean?

A

Simultaneous movement of both eyes in the opposite direction

105
Q

What does convergence mean?

A

Simultaneous adduction movement in both eyes when viewing a near object

106
Q

What does saccade mean?

A

Short fast burst of eye movement up to 900 degrees/sec:

  • Reflexive saccade to external stimuli
  • Scanning saccade
  • Predictive saccade to track objects
  • Memory-guided saccade
107
Q

What is smooth pursuit?

A

Sustained slow movement, up to 60 degrees/sec:

- Driven by motion of a moving target across retina

108
Q

List all the extraocular muscles

A

Medial rectus
Superior rectus
Lateral rectus
Inferior rectus

Superior oblique
Inferior oblique

109
Q

What does contraction of the superior oblique cause?

A

Moves eye in diagonal pattern down and out

Travels through trochlea

110
Q

What does contraction of the inferior oblique cause?

A

Moves eye in diagonal pattern up and out

Travels through trochlea

111
Q

Which extraocular muscles does CN III (oculomotor) innervate?

A

Superior branch:

  • Superior rectus
  • Levator palpebrae superioris

Inferior branch:

  • Inferior rectus
  • Medial rectus
  • Inferior oblique
  • Parasympathetic nerve constricts pupil (circular)
112
Q

Which extraocular muscles does CN IV (trochlear) innervate?

A

Superior oblique

113
Q

Which extraocular muscles does CN VI (abducens) innervate?

A

Lateral rectus

114
Q

How do you test extraocular muscles?

A

Isolate muscle by maximising its action and minimising the action of other muscles

115
Q

What is torsion?

A

Rotation of eye around anterior-posterior axis of eye

116
Q

If you wish to test the superior rectus what position should it be in?

A

Elevated and abducted

117
Q

If you wish to test the inferior rectus what position should it be in?

A

Depressed and abducted

118
Q

If you wish to test the inferior oblique what position should it be in?

A

Elevated and adducted

119
Q

If you wish to test the superior oblique what position should it be in?

A

Depressed and adducted

120
Q

What are the symptoms of 3rd nerve palsy?

A 
Affected eye down and out
Droopy eyelid (loss of elevator palpebrae superioris)
121
Q

What are the symptoms of 6th nerve palsy?

A

Affected eye unable to abduct and deviated inwards

Double vision worsen on gazing to the side of affected eye

122
Q

What is the optokinetic nystagmus reflex?

A

Nystagmus - oscillatory eye movement

Reflex where smooth pursuit tracks an object whilst a fast phase reset saccade also occurs causing a grating motion

123
Q

What/who is the optokinetic nystagmus reflex test used for?

A

Used to test visual acuity in pre-verbal children

Observe the presence of the nystagmus movement in response to moving grating patterns of various spatial frequencies

NEUROLOGY AND NEUROSCIENCE 2 (9 decks)

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