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Year 2 BRS Neuro > Visual System > Flashcards

Visual System Flashcards

1
Q

Duction

A

Duction – Eye Movement in One Eye

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2
Q

‘Simultaneous movement of both eyes in the same direction’

what is this called?

A

Version

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3
Q

_______ : Simultaneous movement of both eyes in the opposite direction

A

Vergence

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4
Q

Convergence

A

– Simultaneous adduction (inward) movement in both eyes when viewing a near object

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5
Q

Saccade

A 
– short fast burst, up to 900°/sec
Reflexive saccade to external stimuli
Scanning saccade
Predictive saccade to track objects
Memory-guided saccade
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6
Q

Lacrimal system

types of tears

A

Basal
Reflex
emotional

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7
Q

Tears - where produced
where do they flow from?
gather?
exit?

A

Drain through two puncta openings on medial lid margin

flow through superior and inferior canaliculi
gather in tear sac
exit via tear duct into nasla cavity

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8
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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9
Q

Reflex tears

A

response to occular irritation , increased tear production

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10
Q

Emotional tear

A

crying

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11
Q

Tear reflex pathway

A

afferent pathway > CNS > Efferent pathway > lacrimal gland
afferent pathway : cornea, CNV1 [ophthalmic trigeminal ]
efferent pathway : parasympathetic innervates lacrimal gland
Neurotransmitter : acetylcholine

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12
Q

What is the ‘Tear Film’ -
Where is it found?
Use?

A

Thin layer of fluid : composed of 3 layers> lipid layer, aqueous> mucious layer

covers healthy cornea, maintaining smooth cornea to air surface

important for maintaining clear vision, removal of debris

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13
Q

Why is the layering of the tear film important?

A

lipid layer allows for reduced tear film evaporation
produced by meibomian glands

aqueous layer important in protection against harmful bacteria ; provides nutrients and oxygen to surrounding tissue

mucinous layer contains mucin

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14
Q

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

A

Conjunctiva

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15
Q

3 layers forming coat of eye?

A

Sclera
Choroid: pigmented vascular
retina : ligh into neuro impulses transmitted to brain via optic nerve

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16
Q

sclera properties

A

high water content

the tough, opaque tissue that serves as the eye’s protective outer coat.

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17
Q

what happens if you hydrate the eye?

A

It becomes white
usually low water content
so can be a clear window to look through / look into eye

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18
Q

how does cornea get oxygen / glucose?

A

oxygen from air

glucose via fluid absorbed by endothelium

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19
Q

uvea

A

lies between sclera and retina

Iris, Ciliary Body, Choroid

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20
Q

How are cataracts formed?

A

Lens losing its transparency with ages resulting in an opaque lens known as Catarct

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21
Q

Most sensitive part of the retina?

A

fovea found within the macula

It has the highest concentration of cones, but a low concentration of rods

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22
Q

Retinal Structure

A

Photoreceptors [1st] > Bipolar Cells [2nd] > Retinal ganglion cells [3rd]

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23
Q

Rods vs Cones

A

Rods : Night vision , 100 times more sensitive to light : 120 mill
Cones: faster response , less sensitivity. fine vision, colour vision 6 million

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24
Q

Deuteranomaly

A

not completely colour blind but they don’t perceive the colour red.

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25
full colour blindness
achromatopsia
26
what is responsible for capturing light rays?
retina
27
where is the macula located?
centrally in the retina,
28
where is the fovea found?
centre of macula
29
peripheral vision?
extensive loss of visual field navigation vision loss shape, movement night vision
30
central vision
detail day vision, colour | fovea has the highest concentration of cone photoreceptors
31
refraction
light goes from one medium to another velocity changes | light bends path changes
32
convex
takes light rays and brinsg them to a point
33
concave lens
diverging lens which takes light rays and spreads them outwards
34
example of a converging lens?
camera | convex lens
35
adequate correction between axial length and refractive power is known as what?
emmetropia
36
ametropia is ?
refractive error | axial length and refractive power mismatch
37
myopia
``` short sight blurred distance vision squinting headache treatment correction with a negative lens contact lens removal of lens to reduce refractive power of the eye by surgery ```
38
hyperopia
Long sighted light rays converge BEHIND retina = blurred NEAR vision so reading eye strain / hence headache why? short globe not enough refractive power
39
hyperopia symptom
visual acuity at near tends to blur relatively early short sight children can get learning difficulty
40
treatment
glasses lens surgery
41
astigmatism
2 focal lines rather 1 focal point - 2 points heredity refractive media is not spherical refract differently as refractive media is not spherical = blurred vision, frontal headache eye strain and pain
42
astigmatism | symptoms
asthenopic symptoms blurred vision distortion of vision head tilting / turning
43
adaptation for near vision
pupillary miosis to increase depth of field convergence to align both eyes towards a near object accommodation to increase the refractive power of the lens for near vision
44
presbyopia
onset 40 onwards naturally occuring loss of accommodation corrected by reading glasses
45
treatment for presbyopia
bifocal glasses trifocal glasses progressive power glasses
46
presbyopia correction
spectacle lenses : monofocal lenses , cylindrical lenses, multifocal lenses
47
signal from Eye to Visual Cortex pathway
``` eye optic nerve optic chiasm optic tract lateral geniculate nucleus optic radiation - 4th order neuron primary visual cortex or striate cortex ```
48
visual pathway retina | first order neurones are ?
rod and cone retinal photoreceptors
49
second order neurons?
retinal bipolar cells
50
third order neurons
retinal ganglion cells
51
what are third order neurons?
optic nerve CN II partial decussation at optic chiasm - 53% optic tract LGN relays visual info to visual cortex
52
where is the lateral geniculate nucleus
thalamus
53
if lesion is found anterior to optic chiasm?
then visual defect is in one eye primarily | i
54
crossed fibres originate
temporal visual field
55
uncrossed fibres
nasal visual field
56
what produces contralateral homonymous Hemianopia?
As a rule, visual pathway lesion posterior to the chiasma produces contralateral Homonymous Hemianopia in both eyes.
57
Bitemporal Hemianopia | causes?
Damage to the crossed nasal ganglion fibres, results in deficit in temporal visual field loss in both eyes simultaneously pituitary adenoma
58
causes of | Homonymous Hemianopia
stroke | Cerebrovascular accident
59
Homonymous Hemianopia | with Macular sparing
stroke causes primary visual cortex damage leads to contralateral homonymous hemianopia but macula is spared - as the area representing it receives dual blood supply from BOTH right and left posterior cerebral arteries
60
shine light pupillary response? which nerve?
pupil constriction decrease spherical abberations&glare mediated by CN III - PARAsympathetic nerve
61
dark | pupillary response?
dilatation increases | mediated by sympathetic nerve : iris radial muscle
62
afferent pathway | draw this out
rod & cone photoreceptors synapse on Bipolar cells > synapse on retinal ganglion cells pupil- specific ganglion cells exits at posterior third of optic tract before entering lateral geniculate nucleus afferent pathway synapses on Edinger-westphal nuclei
63
where is the edinger-westphal nucleus?
brainstem
64
efferent pathway
edinger-westhpal nucelus > occulomotor nerve efferent > synapses at ciliary ganglion short posterior ciliary nerve pupillary sphincter
65
what is the efferent pathway mediated by?
parasympathetic nerve
66
afferent pathway in left eye senses bright light | what happens?
pupillary constriction in both eyes as afferent pathway stimulates efferent pathway of both eyes
67
Pupillary Reflex afferent pathway
A small sub-section of retinal ganglion cells participate in the Pupillary Reflex Pathway. They exit the Optic Tract before the Lateral Geniculate Ganglion, and synapse upon the Dorsal Brain Stem, as shown by the red and green pathways in the diagram
68
consensual light reflex? | why does this happen?
Consensual Light Reflex refers to the constriction of the pupil from the fellow eye. neurological basis : afferent pathway stimulates both efferent pathway
69
efferent defect in left eye | response to light shone in left eye?
right eye constricts left eye unresponsive right eye constricts regardless of light shone in R/L eye
70
afferent right eye defect ? | pupillary response to light?
weak pupillary reflect in both eyes
71
how to demonstrate weakened response ?
stimulate one eye at a time swinging torch test when light is in undamaged eye both pupils are constricted when light is swung to damaged eye, pupils actually dilate as there is relative to the other eye reduced drive for pupillary constriction - damaged afferent pathway unable to process to brainstem that bright light is being shone as it is weak compared to to other eye
72
convergence happens when?
viewing a near object | simultaneous adduction, inward movement of both eyes
73
vergence happens when?
simultaneous movement of both eyes in the opposite direction
74
6 muscles of the eye?
``` 4 straight muscles superior rectus medial rectus lateral rectus inferior rectus ``` superior oblique inferior oblique
75
superior oblique
``` - attached high on temporal side passes under the superior rectus moves eye DOWN & OUT travels through tochlea ```
76
which muscle moves the eye DOWN and OUT?
superior oblique
77
which 3 cranial nerves are involved in eye movements?
CN III CN IV CN VI
78
what is eye movement in one eye called?
Duction
79
what is version?
simultaneous movement of BOTH eyes in Same direction
80
simultaneous movement of BOTH eyes in OPPOSITE direction
vergence
81
which muscle moves eye up?
superior rectus | attached at 12 o'clock
82
inferior rectus | eye movement?
moves eye down
83
where does the lateral rectus attach? | where does it move eye?
temporal side of the eye at 3 o'clock moves eye toward outside of head
84
eye movement | Up and OUT
inferior oblique attached low on the nasal side of the eye diagonal pattern of movement
85
when does Saccade occur?
scanning text when reading a book
86
which muscle doesnt come from a cone at the back of the orbit? where does it come from
inferior oblique | comes in nasally
87
medal rectus
attaches nasal side | moves eye toward the middle
88
which muscle raises the eyelid? | what is it's innervation
levator palpebrae superioris 3rd CN
89
which muscles are innervated by CN III
superior branch- 1) superior rectus, 2) levator palpebrae superioris inferior branch 1) Inferior Rectus – depresses eye 2) Medial Rectus – adducts eye 3) Inferior Oblique – elevates eye 4) Parasympathetic Nerve – constricts pupil
90
depression of eye ?
CN 3 inferior branch inferior rectus muscle
91
superior oblique | innervation
CN IV tochlear depresses eye
92
Abducens | 6th CN
lateral rectus lateral abducts eye
93
what causes adduction?
medial rectus innervated by inferior branch of CN III | Oculomotor nerve
94
when does the oculomotor divide?
when it enters the orbit | divides into superior and inferior
95
lateral rectus muscle testing ?
lateral Rectus muscle action is best tested in the abducted position
96
medial rectus muscle action
Medial Rectus muscle action is best tested in the adducted position.
97
Superior Rectus muscle action
Superior Rectus muscle action is best tested in the elevated and abducted position.
98
Inferior Rectus muscle action
Inferior Rectus muscle action is best tested in the depressed and abducted position.
99
. | Inferior Oblique is best tested
Inferior Oblique is best tested in the elevated and adducted position
100
Superior Oblique is best tested
Superior Oblique is best tested in the depressed and adducted position.
101
Supraduction
Supraduction – one eye
102
Supraversion
Supraversion – both eyes
103
Dextroversion
eye movement to right
104
Levoversion
left eye movement
105
3rd nerve palsy
``` down and out eye droopy eyelid( levator palpebrae superioris) ```
106
why does the eye droop down and out in 3rd nerve palsy
Unopposed superior oblique innervated by fourth nerve (down) | Unopposed lateral rectus action innervated by sixth nerve (out)
107
6th nerve palsy
inability to abduct deviated inwards double vision worsen on gazing to the side of the affected eye

Year 2 BRS Neuro (8 decks)

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