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Neuro yr 2 > visual system > Flashcards

visual system Flashcards

1
Q

what is the little red trinagle on corner of eye called?

A

caruncle

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2
Q

what are the edges of the eye (top lid meets bottom) called?

A

medial and lateral canthus

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3
Q

what is the border between cornea and sclera?

A

limbus

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4
Q

what is the antero-posterior diameter of the eye? (mm)

A

24 mm in adults

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5
Q

3 layers of eye from out to in BACK OF EYE

A

sclera, choroid, retina

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6
Q

sclera structure, qualities and function

A

(its the white) high water content, hard and opaque, protective outer coat

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7
Q

choroid qualities

A

pigmented and vascular

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8
Q

retina - what type of tissue, function, where, describe it structurally.

A

neurosensory tissue: responsible for capturing the light ,

back of eye (“inner part”),

thin

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9
Q

what is uvea

A

ALL AROUND THE WHOLE EYE: Vascular coat of eyeball and lies between the sclera and retina.

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10
Q

3 components of uvea

A

iris, ciliary body (front) and choroid (back)

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11
Q

what is cornea and what is choroid and what is sclera (EASY TO MIX UP)

A

cornea: OUTER LAYER IN FRONT OF IRIS

choroid- middle layer of 3 LAYERS

sclera: white- outer layer

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12
Q

what usually happens when theres disease in one component of uvea and why?

A

spreads to the other components too (not always same extent) because they are very intimately connected

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13
Q

list structures front of eye from out to in

A

cornea
iris
pupil
lens

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14
Q

where is suspensory ligament

A

bellow lens and attatched to it

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15
Q

where is cilliary body

A

over lens and attached to it

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16
Q

where and what is macula? what is at its centre?

A

a little section of the retina at the back centre

highly sensitive- crucual for detailed central vision (ex. required in reading)

fovea at centre

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17
Q

where does the optic nerve connect to RETINA?

A

near macula at back of eye, at optic disc

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18
Q

what is the visible (in an optic exam) portion of the optic nerve called

A

optic disc

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19
Q

what is special about the spot where optic nerve meets retina? (optic disc)

A

there are no light sensitive cells. It is a blind spot

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20
Q

what does central vision entail

A

-detail day vision,
-colour vision
-reading
-facial recognition

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21
Q

where is the highest concentration of cone photoreceptors

A

fovea

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22
Q

what assessment is used for central vision

A

visual acuity (Sharpness) assessment

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23
Q

when do you have poor visual acuity?

A

loss of foveal vision

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24
Q

what features are distinguished by peripheral vision

A

shape, movement, night vision, navigation vision

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25
Q

what activity becomes difficult when theres loss in visual field?

A

navigation (patient may need white stick even with perfect visual acuity)

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26
Q

layers of retina in the order that visual input is processed

A

BE CAREFUL, processing of visual input- light signals starts at the most POSTERIOR layer of the retina (- cones and rods= first order neurons ) EVEN THOUGH light comes from anterior side. see slide 16.

1st order neuron:
photoreceptor - detction of light

second order neuron: bipolar cells
local signal processing to improve contrast sensitivity

3rd motor neuron:
retinal ganglion cells, transmission of signal from eye to brain

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27
Q

two classes of photoreceptors

A

rods and cones

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28
Q

are rods or cones more light sensitive (how much) , fast, many and and why?

A

rods 100x more light sensitive but slower so also more numerically than cones

(120 mil rods, 5 mil cones)

because rods: NIGHT VISION, cones: DAY- FINE vision and colour

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29
Q

what is refraction?

A

change in DIRECTION of any wave when it changes MEDIUM

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30
Q

WHY does direction of wave change in refraction?

A

because velocity changes

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31
Q

what are the 2 types of lenses and what happens to wave of light when it meets them

A

CONVex (CONVerge) -brings rays to a point
concave (diverge) -spreads rays outward

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32
Q

what is the point called where all the rays meet after converging in a convex?

A

focal point

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33
Q

what is emmetropia? where do parallel light rays fall?

A

refractive state in a healthy eye where theres adequate correlation between axial length and refractive power

parallel light rays on the retina

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34
Q

what is ametropia

A

term used to describe general Mismatch between axial length and refractive power

Parallel light rays don’t fall on the retina

includes myopia, (near-sightedness)
hyperopia ( farsightedness)
presbyopia

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35
Q

where do parallel rays converge in myopia and hyperopia

A

myopia: focal point anterior to the retina

hyperopia: .. behind retina

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36
Q

what leads to myopia hyperopia

A

excessive long globe (axial myopia)
or
excessive refractive power: refractive myopia

excessive short globe (axial hyperopia)
insufficient refractive power (refractive hyperopia)

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37
Q

is axial or refractive myopia/ hyperopia more common?

A

axial

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38
Q

why do people get long/ short globe or ref power prob?

A

not clear , genetic factor

39
Q

visual and asthenopic symptoms of myopia

A

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

40
Q

visual and asthenopic symptoms of hyperopia

A

visual acuity at near tends to blur relatively early

nature of blur vary:
1) inability to read fine print 2) near vision is clear but suddenly and intermittently blurry

blurred vision is more noticeable if person is tired , printing is weak or light inadequate

asthenopic symptoms : eyepain, headache in frontal region, burning sensation in the eyes

41
Q

what system is problematic in presbyopia?

A

near response triad

42
Q

what are the 3 muscles involve din near response triad

A

sphincter pupillae
medial recti
circular ciliary muscle

43
Q

what do each of the muscles in nrt do

A

Pupillary Miosis (Sphincter Pupillae) to increase depth of field (think of miosis: polaplasiazei depth)

Convergence (medial recti from both eyes) to align both eyes towards a near object

Accommodation (Circular Ciliary Muscle) to INCREASE THE REFRACTIVE POWER of lens for near vision

44
Q

What is presbyopia? (specifically- why/ how it occurs)

A

Naturally occurring loss of accommodation (focus for near objects)

45
Q

what lens type is in the glasses of poeple with presbyopia

A

(convex lenses) to increase refractive power of the eye

46
Q

onset age of presbyopia

A

40 yrs

47
Q

Which statement is false for Myopia?
A) May be associated with large globe
B) Light ray converges behind the retina
C) May be associated with increased corneal curvature (- increase refractive powers)
D) Unable to see objects clearly at distance without glasses or other optical correction

A

B) Light ray converges behind the retina

48
Q

In accommodation, which one of the following events does not take place?
A) Relaxation of Circular Ciliary Muscle
B) Relaxation of Zonules
C) Thickening of Lens
D) Increase of Lens Refractive Power

A

A) Relaxation of Circular Ciliary Muscle

49
Q

lens thickness, cilliary muscle state and pupil state when looking near

A

contracted ciliary : pushes lens towards centre: thicker
also constricted pupil

50
Q

name of ganglion nerve fibers before optic chiasm (closer to face/ eyes) and after (closer to back of head) chiasm. also what order neurons are these and why

A

before: optic nerve
after: optic tract

this is 3rd order neuron bc 1st and second were IN retina- very small

51
Q

what fibres decussate at chiasm

A

nasal (53%) - the rest just converge (narrow) there

52
Q

where is lateral geniculate nucleus and what happens there

A

after optic chiasm in brain, ganglion fibres synapse

53
Q

what is optic radiation and what does it do

A

4rth order neyuron relay signal form lateral geniculate ganglion to primary visual cortex

54
Q

what comes after primary visual cortex

A

Primary Visual Cortex or Striate Cortex – within the Occipital Lobe, relays to extra-striate cortex (higher visual processing)

55
Q

what happens to ligh impulses after theyve been captured by retina

A

sent to brain via optic nerve

56
Q

what field are the fibres that originate from the nasal visual field responsible for?

A

temporal visual field

57
Q

lesion where in relation to chiasm causes lesion in only one eye

A

in front of chiasm

58
Q

lesion where in relation to chiasm affect both eyes?

A

behind chiasm

59
Q

what happens when lesion at optic chiasm

A

Damages crossed ganglion fibres from nasal retina in both eyes
Temporal Field Deficit in Both Eyes – Bitemporal Hemianopia

60
Q

what happens when right side lesion posterior to optic chiasm

A

Left Homonymous Hemianopia in Both Eyes (bc right fibres- light from left field)

61
Q

what lesion is right nasal hemianopia referring to?

A

lesion in only right optic nerve in right eye

62
Q

what lesion is quadrantanopia

A

lesion behind Lateral Geniculate Nucleus

63
Q

what happens is macular sparing

A

because damage to primary visual cortex is usually due to stroke, AND

the area representing the macula in the eye recieves dual blood supply from posterior cerebral arteries form both sides,

macular vision (central) remains intact while theres contralateral homonymus hemianopia

64
Q

homonymous hemianopia most common cause

A

stroke (cerebrovascular accidnet)

65
Q

3 things that happen in pupil cosntriction in light
(glare? field depth? nerve?)

A

decreases glare
increases depth of field – see Near Response Triad
Pupillary constriction mediated by parasympathetic nerve

66
Q

what is glare

A

Glare refers to the visual discomfort or impairment caused by excessive and uncontrolled brightness or contrast in the field of view.

67
Q

what CN is parasymp nerve part of?

A

3

68
Q

In dark: pupil dilatation, WHTA/ WHY HAPPENS?

A

increases light sensitivity in the dark by allowing more light into the eye
pupillary dilatation mediated by sympathetic nerve

69
Q

which cells participate in the pupillary reflex?

A

A small sub-section of retinal ganglion cells participate in the Pupillary Reflex Pathway.

70
Q

where dos the pathway of the pupillary reflex ganglion cells FIRST deviate form the normal retinal ganglion cells?

A

Pupil-specific ganglion cells exits at posterior third of optic tract before entering the Lateral Geniculate Nucleus

71
Q

what are the synapses involved in the pupillary reflex? (afferent AND efferent)

A

1) primary neurones
synapse with secondary at pretectal neucleus

2) secondary neurones
synapse with tertiary: efferent - PATHWAY FROM EACH EYE HAS SPLIT IN 2 and synapses at the Edinger Westphal nuclei ON BOTH SIDES of the brainstem

3) tertiary neurones: oculomotor nerve efferent
synapses with quaternary neurons at ciliary ganglion

4) quaternary neuron = short posterior ciliary nerve

ends up at effector: pupillary sphincter

72
Q

what is direct and consensual pupillary reflex?

A

Direct Light Reflex – Constriction of Pupil of the light-stimulated eye
Consensual Light Reflex – Constriction of Pupil of the other (fellow) eye

73
Q

why does the consensual reflex happen?

A

Neurological Basis
Afferent pathway on either side alone will stimulate efferent (outgoing) pathway on both sides
(See ipad notes picture or slide 41-2 ppt)

74
Q

what happens when you shed light on right and left eye if theres damage to right optic nerve

A

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

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

75
Q

what happens when right and left eye shed with light in Right Efferent Defect

A

No right pupil constriction (neither eyes) whether right or left eye is stimulated with light
Left pupil constricts (both eyes) whether right or left eye is stimulated with light

76
Q

what does the swinging torch test aim to identify/ diagnose?

A

when damage to afferent pathway is (usually) incomplete, or relative (meaning more than the other eye)

officially called: Relative Afferent Pupillary Defect

77
Q

what do you do in the winging torch test? what do you expect to see if theres a relative afferent pupillary defect?

A

YOU SHED LIGHT on undamaged eye first then on damaged - aim is to compare bc normal eye will constrict and so will the semidamaged eye, just less.

thats why you need to do swinging test, bc if you did separately ud see constriction and think its ok but you wnat to identify the LESS constriction.

when you swing the torch, to you it looks like there has been dilation, this is called “paradoxical dilation.”

78
Q

what are the muscles that move the eye called and how many are there?

A

extraocular muscles: six

79
Q

what nerves are the six extraocular muscles innervated by?

A

CN 3 (occulomotor) , 4 trochlear 6 abducents

80
Q

what muscles in the eye are striated and which are smooth

A

extraoccular: striated
smooth: pupil control

81
Q

what are the areas where striated muscles linked with the periosteum called medially and laterally?

A

medial and lateral enthesis

82
Q

name the 6 extraocular muscles

A

superior and inferior oblique
and 4 straight muscles:
superior , inferior, lateral and medial rectus

83
Q

what direction does superior oblique move eye to

A

down and out (think trochlea is in nose and muscle attaches relatively back of eye not very front)

84
Q

what direction does inferior oblique move eye to

A

up and out

85
Q

how do you test superior/ inferior oblique? (tricky)

A

1)FIRST move eye to look nasally
then
2) ask person to look down for superior and up for inferior obliques

86
Q

what is the medial and lateral sides of eye also clalled?

A

nasal and temporal

87
Q

where does the superior oblique attach on eye?

A

high on temporal side

88
Q

relation of superior oblique to superior rectus in space

A

oblique passes UNDER the superior rectus

89
Q

attatchment of inf oblique on skull

A

Attached low on the nasal side of the eye.

90
Q

relation of inf oblique to inf rectus

A

OVER inf rectus

91
Q

what eye muscles does the third cranial nerve innervate?

A

(2 clear inf/ superior in each of branches and then 2 extras in inf.)

superiorr branch:
superior rectus (raises eye)
levator palpebrae superioris (raises eyelid)

inf branch:
inf rectus
inf oblique
(+ extras:)
parasymp nerve - constricts pupil
medial rectus: adducts eye

92
Q

what does fourth cranial nerve innervate

A

trochlear: superior oblique

93
Q

sixth cranial nerve innervation

A

lateral rectus

94
Q

how do we test superior/ inf rectus muscles?

A

up AND OUT for sup and down AND OUT for inf (the out part is important bc in is for obliques)

Neuro yr 2 (13 decks)

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