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BRS YR2 > Visual system > Flashcards

Visual system Flashcards

1
Q

What are the different parts of the eye?

A
  • upper and lower eyelid
  • lateral and medial canthus
  • palpebral fissure
  • pupil
  • iris
  • sclera
  • caruncle
  • limbus (border between cornea and sclera)
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2
Q

What is the role of tear film?

A
  • maintains smooth cornea-air surface
  • oxygen supply to cornea (cornea is avascular)
  • removal of debris (with blinking)
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3
Q

What is the structure of the tear film?

A
  • lipid layer
  • water layer
  • mucin layer
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4
Q

Describe the superficial lipid layer of the tear film?

A
  • reduce tear film evaporation

- produced by a row of Meibomian Glands along the lid margins

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5
Q

Describe the mucus layer corneal surface of the tear film?

A
  • maintains surface wetting
  • has microvillus and epithelial cells
  • mucin molecules act by binding water molecules,
    to the hydrophobic corneal epithelial cell surface.
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6
Q

What is the role of the aqueous tear film layer?

A
  • delivers oxygen and nutrient to the surrounding tissue

- contains bactericide

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7
Q

Which layer in the tear film protects the tear film from rapid evaporation?

A

lipid layer

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8
Q

What is the conjunctiva?

A

thin, transparent tissue that covers the outer surface of the eye

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9
Q

Where is the conjuctiva?

A

It begins at the outer edge of the cornea, covers the visible part of the eye, and lines the inside of the eyelids

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10
Q

What is the blood supply of the conjunctiva?

A

by tiny blood vessels

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11
Q

What is the sclera?

A
  • tough, opaque tissue that acts as the protective outer coat
  • high water content
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12
Q

What are the 5 layers of the cornea?

A
  • epithelium
  • Bowman’s membrane
  • Stroma
  • Descemet’s membrane
  • Endothelium
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13
Q

What is the role of stroma in the eye?

A

regularity contributes towards transparency

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14
Q

What is the role of the endothelium in the eye?

A

pumps fluid out of the cornea and prevents corneal oedema

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15
Q

What is the cornea?

A
  • transparent, dome shaped window covering the front of the eye
  • low water content
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16
Q

What is the role of the cornea?

A
  • refracting surface

- provides 2/3 of the eye’s focusing power

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17
Q

What are the 3 layers of the coat of the eye?

A
  • sclera
  • choroid
  • retina
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18
Q

What is the role of the sclera?

A
  • protects the eye

- maintains the shape of the eye

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19
Q

What is the choroid?

A

the middle, pigmented vascular layer of the coat

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20
Q

What is the role of the choroid?

A
  • provides circulation to the eye

- shields out the unwanted scattered light

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21
Q

What is the retina?

A

the innermost neurosensory layer

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22
Q

What is the role of the retina?

A

responsible for converting light into neurological impulses, transmitted to the brain by the optic nerve

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23
Q

What is the uvea?

A

vascular coat of eyeball

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24
Q

Where is the uvea?

A

between the sclera and retina

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25
Q

What are the 3 parts that make up the uvea?

A
  • iris
  • ciliary body
  • choroid
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26
Q

What is the role of the iris?

A

controls light levels inside the eye

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27
Q

What is the iris?

A
  • coloured part of the eye

- embedded with tiny muscles that dilate and constrict the pupil size

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28
Q

What is the role of the human lens?

A

responsible for 1/3 of the refractive power of the eye

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29
Q

What is the structure of the lens?

A
  • outer acellular capsule

- regular inner elongated cell fibres

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30
Q

What can happen to lens with age?

A
  • opacification

- cataract

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31
Q

What is the retina?

A

thin layer of tissue that lines the inner part of the eye

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32
Q

What is the role of the retina?

A

responsible for capturing the light that enters the eye, sent to brain, via the optic nerve

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33
Q

What is the role of the optic nerve?

A

transmits electrical impulses from the retina to the brain

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34
Q

Where is the optic nerve?

A
  • connects to the back of the eye near the macula

- the visible portion of the optic nerve, is the optic disc

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35
Q

Where is the blind spot?

A

on the optic disc

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36
Q

What is the macula?

A

a small and highly sensitive part of the retina

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37
Q

What is the role of the macula?

A
  • responsible for detailed central vision

- central vision (like reading)

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38
Q

Where is the macula?

A

in the centre of the retina, temporal to the optic nerve

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39
Q

What is the fovea?

A

the centre of the macula

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40
Q

What is the structure of the fovea?

A
  • highest concentration of cones

- low concentration of rods

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41
Q

What is central vision?

A
  • responsible for central fine vision and daytime colour vision
  • also known as macular vision
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42
Q

How does loss of central vision present?

A

problems with:

  • reading
  • recognising facfes
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43
Q

What is used to assess central vision?

A

visual acuity assessment

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44
Q

What is the role of peripheral vision?

A

detecting:

  • shape
  • movement in the environment
  • night vision
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45
Q

How does loss of peripheral vision present?

A

problems navigating the world

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46
Q

What is used to assess peripheral vision?

A

visual field assessment

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47
Q

What are the 3 layers of the retina?

A 
Retinal pigment epithelium
Neuroretina:
- outer layer of photo-receptor
- middle layer of intermediate neurons
- inner layer of ganglion nerve cells
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48
Q

What is the role of the outer layer of the neuroretina?

A
  • photoreceptors (1st order neuron)

- detection of light

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49
Q

What is the role of the middle layer of the neuroretina?

A
  • bipolar cells (2nd order neuron)

- local signal processing to improve contrast sensitivity, and regulate sensitivity

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50
Q

What is the role of the inner layer of the neuroretina?

A
  • retinal ganglion cells (3rd order neurons)

- transmission of the signal from the eye to the vbrain

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51
Q

What is the outermost layer of the retina?

A

retinal pigment epithelium

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52
Q

What is the role of the retinal pigment epithelium?

A
  • nutrient transport from the choroid to the photo receptor cells
  • removes metabolic waste from the retina
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53
Q

What are the 2 main types of photoreceptors?

A
  • rods

- cones

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54
Q

What is the structure of rods?

A
  • Longer outer segment with photo-sensitive pigment
  • 100 times more sensitive to light than cones
  • Slow response to light
  • 120 million rods
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55
Q

What are rods responsible from?

A

Responsible for night vision (Scotopic Vision)

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56
Q

What are cones responsible for?

A
  • Less sensitive to light, but faster response
  • Responsible for day light fine vision and colour vision (Photopic Vision)
  • 6 million cones
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57
Q

Where are photopigments synthesized?

A

inner photo-receptor segment, and then transported to the outer segment

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58
Q

What is the structure of the outer segment of photoreceptors?

A
  • stacks of discs
  • distal discs with deactivated photo-pigments (shedded from the tips)
  • phago-cytosed by the retinal epithelial cells
  • deactivated photopigments are regenerated inside the retinal epithelial cells,
    and then transported back to the photo-receptors.
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59
Q

Where are rods found?

A
  • widely distributed all over the retina
  • highest density outside the macula
  • density decreases towards the periphery
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60
Q

Where are cones found?

A

distributed only in the macula

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61
Q

Where can one find the highest concentration of Rod photoreceptors in the retina?

A

20-40 degrees away from the fovea

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62
Q

What are the three sub-types of cones?

A
  • S-Cones (short wavelength) - colour blue,
  • M-Cones (medium wavelength) - colour green,
  • L-Cones (long wavelength) - colour red.
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63
Q

What does yellow light stimulate?

A
  • M-cones and L-cones equally
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64
Q

What is the most common form of colour vision deficiency?

A

Deuteranomaly

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65
Q

What causes Deuteranomaly?

A

the shifting of the M-cone sensitivity peak towards that of the L-cone curve,
causing red-green confusion

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66
Q

What is the term given to full colour blindness?

A

Achromatopsia

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67
Q

What is Anomalous trichromatism?

A

colour vision deficits can be caused by a shift in the photo-pigment peak sensitivity

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68
Q

What is Dichromatism?

A

when only 2 cone photo-pigment sub-types are present

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69
Q

What is Monochromatism?

A

complete absence of colour vision

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70
Q

What is Blue cone monochromatism?

A

the presence of only blue L-cones

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71
Q

What do patients with Blue Cone Monochromatism experience?

A

normal day light visual acuity

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72
Q

What is Rod Monochromatism?

A

a total absence of all cone photo-receptors

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73
Q

What do patients with Rod Monochromatism experience?

A

no functional day vision

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74
Q

Where is the lacrimal gland?

A
  • in the orbit

- latero-superior to the globe

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75
Q

What does the lacrimal gland do?

A

It produces tear at a constant level,

even in the absence of irritation or stimulation.

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76
Q

What is a Basal tear?

A

It produces tear at a constant level,

even in the absence of irritation or stimulation.

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77
Q

What is a Reflex tear?

A

the increased tear production,

in response to ocular irritation.

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78
Q

What is the tear reflex pathway composed of?

A
  • the afferent pathway
  • the central nervous system
  • the efferent pathway
  • the lacrimal gland.
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79
Q

What innervates the cornea?

A

by the sensory nerve fibres via the Ophthalmic Branch of the Trigeminal Nerve

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80
Q

What is the afferent pathway involved in the tear reflex?

A

the trigeminal nerve relays signal to the CNS

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81
Q

What is the efferent pathway involved in the tear reflex?

A

the parasympathetic nerve

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82
Q

What innervates the lacrimal gland?

A

The lacrimal nerve, from the ophthalmic branch of the trigeminal nerve

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83
Q

How does the tear film drain to eye from the lacrimal gland?

A
  • drains through the 2 puncta, openings on the upper and lower medial lid margins
  • flow through superior and inferior canalculi
  • both canalculi converge as a common canaliculus, drain tear into the tear sac
  • exits sac thrrough tear duct into nasal cavity
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84
Q

What happens if you hydrate the cornea?

A

it whitens

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85
Q

How do you test for colour blindness?

A

Ishihara test

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86
Q

What are the 2 types of lenses?

A
  • converging (convex)

- diverging (concave)

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87
Q

What is a converging lens?

A
  • convex

- takes light rays and bring them to a point

88
Q

What is a diverging lens?

A
  • concave

- takes light rays and spreads them outward

89
Q

What is Ametropia?

A

mismatch between axial length and refractive power

light doesn’t fall on the retina

90
Q

What are the different types of Ametropia?

A
  • near sightedness (myopia)
  • far sightedness (hyperopia)
  • astigmatism
  • presbyopia
91
Q

What is the mechanism of myopia?

A

parallel rays converge at a focal point anterior to the retina

92
Q

What are the causes of myopia?

A
  • excessive long globe (axial myopia)

- excessive refractive

93
Q

What are the symptoms of myopia?

A
  • Blurred distance vision
  • Squint in an attempt to improve uncorrected visual acuity when gazing into the distance
  • Headache
94
Q

How do you treat myopia?

A
  • Correction with diverging lenses (negative lenses)
  • Correction with contact lens
  • Correction by removing the lens to reduce refractive power of the eye
95
Q

What is hyperopia?

A

Parallel rays converge at a focal point posterior to the retina

96
Q

What are the causes of hyperopia?

A
  • excessive short globe (axial hyperopia)

- insufficient refractive power (refractive hyperopia)

97
Q

What are the symptoms of hyperopia?

A
  • visual acuity at near tends to blur relatively early
  • nature of blur is vary from inability to read fine print to near vision is clear but suddenly and intermittently blur
  • blurred vision is more noticeable if person is tired , printing is weak or light inadequate
  • eyepain
  • headache in frontal region
  • burning sensation in the eyes
  • blepharoconjunctivitis
98
Q

What is Amblyopia?

A

reduced vision in one eye caused by abnormal visual development early in lif

99
Q

What is the treatment for Hyperopia?

A
  • Correction with converging (positive lenses)
  • Correction with positive lens + cataract extraction
  • Correction with contact lens
  • Correction with intraocular lens
100
Q

What is the mechanism of Astigmatism?

A

Parallel rays come to focus in 2 focal lines rather than a single focal point

101
Q

What is the cause of Astigmatism?

A
  • hereditary
  • refractive media is not spherical, refract differently along one meridian than along meridian
  • perpendicular to it–>2 focal points (punctiform object is represent as 2 sharply defined lines)
102
Q

What are the symptoms of an Astigmatism?

A
  • headache
  • eye pain
  • blurred vision
  • distortion of vision
  • head tilting and turning
103
Q

What is the treatment for an Astigmatism?

A

regular:
- cylinder lenses with or without spherical lenses (convex or concave), Sx
irregular:
- rigid cylinder lenses, surgery

104
Q

What is Presbyopia?

A
  • Naturally occurring loss of accommodation (focus for near objects)
  • distant vision intact
105
Q

When does Presbyopia start to develop?

A

onset from 40 years old

106
Q

How do you treat Presbyopia?

A
  • reading glasses (convex lenses) to increase refractive power of the eye
  • spectacle lens (Monofocal lenses : spherical lenses, cylindrical lenses, Multifocal lenses)
  • contact lenses
107
Q

What are the benefits of using contact lenses?

A

higher quality of optical image and less influence on the size of retinal image than spectacle lenses

108
Q

What are the indications to use contact lenses?

A
  • cosmetic
  • athletic activities
  • occupational
  • irregular corneal astigmatism
  • high anisometropia
  • corneal disease
109
Q

What are the disadvantages of using contact lenses?

A
  • careful daily cleaning and disinfection

- expensive

110
Q

What are the possible complications associated with contact lenses?

A
  • infectious keratitis
  • giant papillary conjunctivitis
  • corneal vascularization
  • severe chronic conjunctivitis
111
Q

What are intraocular lenses?

A

replacement of cataract crystalline lens

112
Q

What are the benefits of using intraocular lenses?

A
  • best optical correction for aphakia

- avoid significant magnification and distortion caused by spectacle lenses

113
Q

What happens in accomodation?

A
  • Relaxation of Zonules
  • Thickening of Lens
  • Increase of Lens Refractive Power
114
Q

What is the Staar intra-collamer lens (ICL) used to treat?

A

correction of the myopia and astigmatism

115
Q

Where is a Staar intra-collamer lens (ICL) placed?

A

in between the iris and natural lens of the eye

116
Q

What is Emmetropia?

A
  • normal eye

- adequate correlation between axial length and refractive power

117
Q

What is the purpose of Near Response Triad?

A

adaptation for near vision

118
Q

What is the Near Response Triad?

A
  • Pupillary Miosis
  • Convergence
  • Accomodation
119
Q

What happens in Pupillary Miosis?

A

sphincter pupillae cause the pupil to constrict, increasing the depth of field

120
Q

What happens in Convergence?

A

medial recti contract, adducting the eyes to align both eyes towards a near object

121
Q

What happens in Accomodation?

A

circular ciliary muscle acts, allowing the lens to accommodate (increase refractive power of lens for near vision)

122
Q

What are the possible surgeries to correct refractive errors?

A
  • Keratoreactive surgery, eg: LASIK

- Intraocular surgery: clear lens extraction, IOL

123
Q

What happens in LASIK?

A
  • cutting of the corneal flap
  • Flipping of corneal flap
  • Photorefractive treatment (laser)
  • Corneal stroma reshaped post laser
  • Corneal flap back in position
124
Q

What happens in clear lens extraction + IOL?

A
  • same as cateract extraction

- implantation of artificial lens

125
Q

What is the disadvantage of a clear lens extraction +IOL?

A

lose accommodation, patient will need reading glasses

126
Q

What is a Phaco tip?

A

US tip that breaks down the lens and removes it

127
Q

What is the role of the visual pathway?

A

transmits signal from eye to the visual cortex

128
Q

What are the landmarks of the visual pathway?

A
  • Eye
  • Optic Nerve – Ganglion Nerve Fibres
  • Optic Chiasm – Half of the nerve fibres cross here
  • Optic Tract – Ganglion nerve fibres exit as optic tract
  • Lateral Geniculate Nucleus, Ganglion nerve fibres synapse at Lateral Geniculate Nucleus
  • Optic Radiation – 4th order neuron
  • Primary Visual Cortex or Striate Cortes – within the Occipital Lobe
129
Q

What relays information to the visual cortex?

A

Lateral Geniculate Nucleus in Thalamus

130
Q

What is the impact of a lesion anterior to the optic chiasma?

A

affects the visual field in only one eye

131
Q

What is the impact of a lesion posterior to the optic chiasma?

A

affects the visual field in both eyes

  • Right sided lesion: Left Homonymous Hemianopia in Both Eyes
  • Left sided lesion: Right Homonymous Hemianopia in Both Eyes
132
Q

What are the nerves that cross at the optic chiasma responsible for?

A

temporal visual field

133
Q

What are the nerves that do not cross at the optic chiasma responsible for?

A

the nasal visual field

134
Q

What is the impact of a lesion at the optic chiasma?

A

temporal field deficit in both eyes - bitemporal hemianopia

135
Q

What can cause a bitemporal hemianopia?

A

enlargement of a pituitary gland tumour

136
Q

What can cause a homonymous hemianopia?

A

stroke (cerebrovascular accident)

137
Q

What can damage to the primary visual cortex due to stroke cause?

A

Homonymous Hemianopia of the contralateral side, with sparing of macula central vision

138
Q

Why is damage to the primary visual cortex unlikely?

A

receives dual blood supply from both right and left posterior cerebral arteries

139
Q

What happens to the pupil in light?

A

pupil constrict

140
Q

Why does the pupil constrict under light?

A
  • decreases spherical aberrations and glare
  • increases depth of field
  • reduces bleaching of photo-pigments
141
Q

What mediates pupillary constriction?

A

parasympathetic nerve (within CNIII), causing circular muscles to contract

142
Q

What happens to the pupil in dark?

A

pupil dilation

143
Q

Why does the pupil dilate in the dark?

A

increases light sensitivity in the dark by allowing more light in

144
Q

What mediates pupillary dilation?

A

the sympathetic nerve, causing radial muscles to contract

145
Q

What happens in the afferent pathway of the pupillary reflex?

A
  • Rod and Cone Photoreceptors synapsing on Bipolar Cells synapsing on Retinal Ganglion Cells
  • Pupil-specific ganglion cells exits at posterior third of optic tract before entering the Lateral Geniculate Nucleus
  • Afferent (incoming) pathway from each eye synapses on Edinger-Westphal Nuclei on both sides in the dorsal brainstem
146
Q

What happens in the efferent pathway of the pupillary reflex?

A
  • Edinger-Westphal Nucleus
  • Oculomotor Nerve Efferent
  • Synapses at Ciliary ganglion upon the Short Posterior Ciliary Nerve
  • Pupillary Sphincter
147
Q

What stimulates the efferent pathway on both eyes?

A

the afferent pathway for either eye

148
Q

What is the direct light reflex?

A

constriction of the pupil of the light-stimulated eye

149
Q

What is the consensual light reflex?

A

constriction of the pupil of the other eye (light shone in opposite eye to this one)

150
Q

What happens if the right afferent pupillary pathway is damaged?

A
  • stimulation of the right eye will elicit weak,
    or no pupillary constriction in both eyes.
  • BUT, Normal pupil constriction in both eyes when left eye is stimulated with light
151
Q

What happens if the right efferent pupillary pathway is damaged?

A

no pupillary constriction in the right eye, and normal pupillary constriction in the left eye, whether right eye or left eye is stimulated.

152
Q

How do you detect a relative afferent pupillary defect?

A

swinging torch test

153
Q

What happens in a swinging torch test?

A
  • Both pupils constrict,
    when light swings to the left eye with intact afferent pathway.
  • Both pupils will paradoxically dilate,
    when the light swings to the right eye with damaged afferent pathway, as a result of relatively reduced drive for pupillary constriction in both eyes.
154
Q

What is duction?

A

eye movement in one eye

155
Q

What is version?

A

simultaneous movement of both eyes in the same direction

156
Q

What is vergence?

A

simultaneous movement of both eyes in the opposite direction

157
Q

What is convergence?

A 
simultaneous adduction (inward) movement in both eyes when viewing a near object
(angle greater at a near target)
158
Q

What are the 2 different types of eye movement?

A
  • saccade (short, fast burst)

- smooth pursuit (sustain, slow movement)

159
Q

What is saccade?

A
  • Reflexive saccade to external stimuli
  • Scanning saccade
  • Predictive saccade to track objects
  • Memory-guided saccade
160
Q

What is smooth pursuit eye movement?

A
  • Slow movement – up to 60°/s

- Driven by motion of a moving target across the retina.

161
Q

What are the 6 muscles of the eye?

A
  • medial rectus
  • lateral rectus
  • superior rectus
  • inferior rectus
  • superior oblique
  • inferior oblique
162
Q

What are the 4 straight muscles of the eye?

A
  • medial rectus
  • lateral rectus
  • superior rectus
  • inferior rectus
163
Q

What is the role of the superior rectus?

A

moves the eye up

maximally in abducted position

164
Q

What is the role of the inferior rectus?

A

moves the eye down

maximally in abducted position

165
Q

What motion do the superior and inferior rectus cause when the eye is adducted?

A

torsion motion

166
Q

Where is the lateral rectus attached?

A

temporal side of the eye

167
Q

What is the role of the lateral rectus?

A

moves the eye towards the outside of the head (towards the temple)

168
Q

Where is the medial rectus attached?

A

on the nasal side of the eye

169
Q

What is the role of the medial rectus?

A

moves the eye toward the middle of the head (towards the nose)

170
Q

Where is the superior oblique attached?

A
  • high on the temporal side of the eye
  • passes under the superior rectus
  • travels through the trochlea
171
Q

What is the role of the superior oblique?

A

moves the eye in a diagonal pattern, down and out

172
Q

Where is the inferior oblique attached?

A
  • attached low on the nasal side of the eye

- passes over the inferior rectus

173
Q

What is the role of the inferior oblique?

A

moves the eye in a diagonal pattern, up and out

174
Q

What innervates the lateral rectus?

A

CN 6 - abducens nerve

175
Q

What innervates the superior oblique?

A

CN 4 - trochlear nerve

176
Q

What innervates the superior rectus?

A

CN 3 - superior branch of the oculomotor nerve

177
Q

What is innervated by CN3 (oculomotor nerve)?

A
  • levator palpebrae superioris (raises eyelid)

- superior rectus

178
Q

What innervates the inferior rectus?

A

CN 3 - inferior branch of the oculomotor nerve

179
Q

What innervates the medial rectus?

A

CN 3 - inferior branch of the oculomotor nerve

180
Q

What innervates the inferior oblique?

A

CN 3 - inferior branch of the oculomotor nerve

181
Q

What innervates pupil constriction?

A

CN 3 - the parasympathetic branch of the inferior oculomotor nerve

182
Q

How do you test the action of the inferior rectus muscle?

A

depressed and abducted position

183
Q

How do you test the action of the superior rectus muscle?

A

elevated and abducted position

184
Q

How do you test the action of the medial rectus muscle?

A

adducted position

185
Q

How do you test the action of the lateral rectus muscle?

A

abducted position

186
Q

How do you test the action of the inferior oblique muscle?

A

elevated and adducted position

187
Q

How do you test the action of the superior oblique muscle?

A

depressed and adducted position

188
Q

What is supraduction?

A

elevation of one eye

189
Q

What is supraversion?

A

elevation of both eyes, simultaneously

190
Q

What is infraversion?

A

depression of both eyes, simultaneously

191
Q

What is infraduction?

A

depression of one eye

192
Q

What is abduction?

A

refers to duction movement of one eye, moving away from the nose.

193
Q

What is adduction?

A

to duction movement of one eye, moving towards the nose.

194
Q

What is dextroversion?

A

involves simultaneous right eye abduction, and left eye adduction.

195
Q

What is levoversion?

A

involves simultaneous left eye abduction, and right eye adduction.

196
Q

What is torsion?

A

rotation of eye around the anterior-posterior axis of the eye

197
Q

How does third nerve palsy present?

A
  • Affected eye down and out
  • Droopy eyelid (loss of elevator palpebrae superioris)
  • Unopposed superior oblique innervated by fourth nerve (down)
  • Unopposed lateral rectus action innervated by sixth nerve (out)
198
Q

What muscles are affected in third nerve palsy?

A

everything but:

  • lateral rectus (abduction)
  • superior oblique (depression)
199
Q

How does sixth nerve palsy present?

A
  • Affected eye unable to abduct and deviates inwards

- Double vision worsen on gazing to the side of the affected eye

200
Q

What is Nystagmus?

A

oscillatory movement of the eye

201
Q

What is Opto-kinetic Nystagmus?

A

physiological nystagmus,

triggered by the presentation of a constantly moving grating pattern.

202
Q

How does Opto-kinetic Nystagmus look?

A

The eyes track along the grating motion, with smooth pursuit up to a limit, and resets the eye position to the centre, with a burst of fast saccade motion.

203
Q

What does the presence of Opto-kinetic Nystagmus suggest?

A

the subject has sufficient visual acuity to perceive the grating

204
Q

What can cause a constant dilated pupil?

A
  • overaction of the sympathetic nervous system (causes mydriasis via dilator pupillae)
  • underaction of parasympathetic nervous system (causes miosis via sphincter pupillae).
205
Q

What are the 2 different forms of lesions?

A
  • medical

- surgical

206
Q

What are medical CN3 lesions?

A
  • the vasculature to the nerve (the central portion of the nerve)
  • tend to not affect the pupil (‘pupil sparing’) as the parasympathetic fibres running to the eye are in the outer portion of the nerve.
207
Q

What are surgical CN3 lesions?

A

compresses the outer portion of the nerve fibres, which is where the parasympathetic nerves run (affecting the pupil)

208
Q

What can cause a medical CN3 lesion?

A

microvascular disease due to hypertension, T2DM

209
Q

What can cause a surgical CN3 lesion?

A
  • posterior communicating artery aneurysm

- In relation to the Circle of Willis: CN3 runs in between the posterior cerebral and the superior cerebellar artery.

210
Q

How do you treat a medical CN3 lesion?

A

better metabolic control of their condition

211
Q

How do you treat a surgical CN3 lesion?

A

assessment of aneurysm

may involve clipping

212
Q

What could cause tonically dilated pupil in the right eye. Upon shining light into the right eye, the pupil is slow to react compared to the left. The left eye reacts when light is shone into the right eye. ?

A
  • Damage to parasympathetic ciliary ganglion which is involved in the pupillary-light reflex.
  • Parasympathetic fibres travel with CNIII (oculomotor) to synapse at the ciliary ganglion before innervating the iris and ciliary body.
213
Q

What site of damage can cause absent reflexes and impaired sweating?

A

dorsal root ganglia of the spinal cord

214
Q

How does pilocarpine work?

A

a muscarinic receptor agonist that acts on M3 receptors in the iris sphincter muscle. This results in contraction of the muscle (miosis) and constriction of the pupil. These are independent of the parasympathetic tract.

215
Q

What is an Adie’s pupil?

A
  • light-near dissociation

- reinnervation that takes place as a result of damage to the ciliary ganglion

216
Q

what causes there innervation that takes place as a result of damage to the ciliary ganglion?

A
  • involves up regulation of postsynaptic receptors but the reinnervation is aberrant, causing fibres directed for the ciliary body to end up targeting the iris.
  • As a result, the patient develops more meiosis with near accommodation than they do to light.

BRS YR2 (70 decks)

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