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6a > Eye > Flashcards

Eye Flashcards

1
Q

Volitional saccades

A

conscious/free will

can be a screen for higher cortical function

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2
Q

Anti-saccade

A

consciously looking away from a stimulus

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3
Q

Memory saccade

A

remember spot, put gaze to where object was

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4
Q

Reflexitve saccades

A

looking at object of interest reflexively

coordinated through midbrain

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5
Q

Reflexive saccade pathway (object in the left)

A

Left visual field –> Right LGN of thalamus –> Right primary visual cortex, visual association cortex, frontal eye fields etc
–> R superior colliculus –> PPRF –> gaze to the left

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6
Q

Superior colliculus saccade

A

Retina –> visual layer of colliculus –> motor layer of colliculus –> gaze centres

Motor layer of colliculus receives extrapyramidal input

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7
Q

Pursuit movement components

A

cortical information from primary visual cortex/frontal eye fields
Cerebellar information for proprioception to stabilize information
Vestibular information to orient

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8
Q

CN III innervations

A

pupil
levator muscle
IO, SR, MR, IR
NOTE: nerve palsy –> unilateral ptosis, mydriasis is never nuclear

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9
Q

inferior rectus nucleus

A

dorsal - ipsilateral

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10
Q

Inferior oblique nucleus

A

intermediate - ipsilateral

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11
Q

medial rectus nucleus

A

ventral - ipsilateral

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12
Q

CN III location

A

intramedullarily related to: red nucleus (cerebellar connections) and cerebral peduncle (pyramidal tract)
tentorium and MCA/PCom jxn
cavernous sinus and pituitary
Superior orbital fissure and orbit

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13
Q

CN IV location

A

long course from dorsum of brainstem

through cavernous sinus and adjacent to pituitary gland

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14
Q

CN VI location

A

over petrous ridge

through cavernous sinus and adjacent to pituitary gland

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15
Q

Sup Rectus function

A

elevation and intorsion abduction

intorsion increase with adduction

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16
Q

Inf rectus function

A

depression and extorsion abduction

extorsion increases with adduction

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17
Q

Inferior oblique function

A

elevation and extorsion adduction

extorsion increases with abduction

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18
Q

Superior oblique function

A

depression and intorsion adduction

intorsion increases with abduction

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19
Q

Fixation system

A

Maintain fixation on a stationary target
Micromoevments to moev objects of regard on fovea
Necessary for vision
poorly localized in cortex

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20
Q

Fixation system dysfunction

A

global confusional states and dementia
anxiety
sedative/tranquilizers

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21
Q

Saccadic system

A

movement between targets on command
voluntary and fast eye movements
contralateral frontal cortex - projects via internal capsule to brainstem gaze centre

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22
Q

Saccade dysfunction

A

unilateral: horizontal gaze palsy
Bilateral: vertical gaze palsy
Disorders commonly seen (e.g. MCA infarct)

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23
Q

Pursuit system

A

tracking a slowly moving target
slow, involuntary eye movements
Occipital-parietal cortex
projects via internal capsule to brainstem

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24
Q

Pursuit dysfunction

A

cogwheel pursuit

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25
Q

Vergence system

A

occipital-parietal to midbrain pre-tectum

slow disconjugate eye movements

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26
Q

Non-optic reflex system

A

Oculocephalic reflex
caloric responses
Slow eye movements
Brainstem vestibular system

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27
Q

Frontal gaze palsy

A

horizontal gaze palsy (uses frontal eye field)
pursuit is ok (doesn’t use frontal eye field)
nuclei/downstream are okay
Dolls eyes movements
CT scan lesion
Look toward their lesion
Conjugate eye movements - no diplopia

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28
Q

Progressive supranuclear palsy (PSP)

A 
gradual impairment of supranuclear gaze
Vertical > horizontal
Voluntary > pursuit > reflex
relatively preserved vertical movements in non-optic reflexes
axial dystonia
dementia
no convergence
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29
Q

Perinaud’s syndrome

A

vertical gaze palsy - can’t look up
lid retraction/ptosis
convergence-retraction nystagmus (all eye movements fire at the same time)
convergence poor, light reflex poor
lesion in pineal region compressing dorsal midbrain

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30
Q

Intranuclear ophthalmoplegia

A

Ipsilateral adduction weakness (MR)
MLF lesion - demyelination of heavily myelinated tract
could cause bilateral MLF lesions (MS hallmark)
Contralateral abducting nystagmus - vergence system attempt to compensate

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31
Q

Complete CN III palsy SSx

A

paralysis of all extraocular muscles except LR and SO
some abduction/depression/intorsion remain
–> down and out position at rest
pupil dilated and unresponsive to light –> involvement of parasympathetic fibers

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32
Q

CN III palsy cause

A

internal carotid artery aneurysm a common cause

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33
Q

CN VI palsy

A

horizontal diplopia

some patinets may tend to turn head toward affected eye to compensate

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34
Q

Choroid

A

vascular dark brown membrane (with melanin)

reduces light scatter within the eye

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35
Q

Ciliary body

A

ring of SM control eye movement via suspensory ligament

focusing vision

36
Q

Outer pigmented layer (RPE) of the retina

A

absorbs light and prevents light scatter

role in photoreceptor regeneration

37
Q

Inner neural layer of the retina

A

contains photoreceptors and neurons

38
Q

Uveitis

A

more serious
often associated with systemic disease (autoimmune, infections, etc)
can be segmental

39
Q

Blood supply to the eye

A

from internal carotid
ophthalmic artery arises at carotid siphon in cavernous sinus
2 end branches:
- posterior ciliary arteries (choroid, outer retina, optic disc)
- central retinal artery (inner retina)

40
Q

Anterior ischemic optic neuropathy

A

due to ischemia in posterior ciliary arteries

see swollen infarcted optic disc, greyish

41
Q

Central retinal artery occlusion

A

pale retina with a cherry red spot at fovea from shine-through of choroid
little inner retina at fovea

42
Q

Rods

A

provide scotopic vision (dim light) - high sensitivity in the dark
Low spatial resolution - summation to one bipolar cell
Rhodopsin pigment

43
Q

Cones

A

provide photopic vision (bright light)
colour vision - reflects type of opsin; R, G, B
X-chromosome
High resolution central vision

44
Q

Photopigment

A

opsin + retinal

45
Q

Phototransduction cascade

A

1) a photon converts 11-cis-retinal –> all-trans-retinal
2) activation of hundreds of G-protein transducin
3) transducin activates cGMP phosphodiesterase
4) each breaks down thousands of cGMP
5) decrease in [cGMP] closes Na channel –> hyperpolarization

46
Q

Photoreceptor distribution

A

Fovea: no rods, just cones
Rods highest density at 20 degrees eccentricity
Rods/cones decline in density with increasing eccentricity

47
Q

Physiologic blind spot

A

at the optic disc
Retinal ganglion cells gather to form optic nerve
no photoreceptors

48
Q

Cone dystrophy/macular degeneration

A

central scotoma with poor central daytime vision

49
Q

Retinitis pigmentosa

A

disease of rods

causes ring scotomata and nyctalopia (night blindness)

50
Q

Bipolar cell - relay

A

from photoreceptors to retinal ganglion cells
Glutamate stimulation from photoreceptors
different bipolar cells for rods/cones
OFF/ON cells
Graded EPSP, not actional potential

51
Q

OFF bipolar cells

A

active without light, excited by glutamate

52
Q

ON bipolar cells

A

active with light, inhibited by glutamate (light reduces glutamate release)

53
Q

Modulation of bipolar cells

A

by horizontal cells (at photoreceptor/bipolar cell synapse)
+ amacrine cells (at bipolar cell/retinal ganglion cell synapse)

Lateral inhibition by light in neighbouring regions –> centre-surround receptive organization

54
Q

Parvocellular retinal ganglion cells

A 
small cell bodies
short dendrites
small receptive fields
sustained response to onset of light
--> high spatial resolution, low temporal resolution

colour opponency

55
Q

Magnocellular retinal ganglion cells

A

large cell bodies
long dendrites
large receptive fields
respond transiently to onset/offset of light
–> low spatial resolution, high temporal resolution

56
Q

Papillomacular bundle

A

large bundle of RGC axons from fovea and macula

57
Q

Temporal raphe

A

divides RGC fibers from upper and lower temporal retina (nasal visual field)
because they must curve around the large papillomacular bundle that is in the way

58
Q

RGC fibers from nasal retina

A

temporal visual field

head straight to the optic disc

59
Q

Central scotoma

A

optic neuritis

info from fovea –> disc all gone

60
Q

Ceco-central scotoma

A

lesion closer to blind spot

hole contains lesion + blind spot

61
Q

Nasal arcuate defect

A

inferior/superior reversed
lesion in arching fibers
e.g. glaucoma

62
Q

Temporal wedge defect

A

on the other side of the blind spot

rare

63
Q

Optic nerve

A

component of CNS
myelin provided by oligodendrocytes
each optic nerve ~106 axons
pass into cranium through optic canal, converge above pituitary at optic chiasm

64
Q

Optic tract

A

continuation from optic chiasm
contains information from the contralateral hemifield of each eye
terminates in LGN

65
Q

Pretectal nuclei

A

midbrain

pupil light reflex

66
Q

Superior colliculus (vision)

A

rapid eye/head orientation

reflexive eye movements

67
Q

Nucleus of optic tract/accessory optic system

A

supplement vestibular information in keeping gaze stable

68
Q

Suprachiastmatic nuclei

A

hypothalamus

diurnal regulation of homeostasis

69
Q

Lesions of optic chiasm

A

Bitemporal hemianopia
almost always due to mass effect, often a pituitary tumour
loss of nasal retinal fibers from both eyes

70
Q

Lesions of optic tract

A

homonymous hemianopia
affect nasal fibers from the contralateral eye, temporal fibers from the ipsilateral eye.
Contralateral visual filed information lost

Usually partial and usually incongruous

71
Q

Lesion to the Meyer loop

A

Contralateral superior quadrantanopia

fibers from upper portion of the contralateral visual field from both eyes

72
Q

Lesion to the optic radiations

A

Contralateral inferior quadrantanopia

73
Q

Lesion to the primary visual cortex

A

Contralateral homonymous hemianopia

loss of visual info from contralateral visual field

74
Q

LGN layers

A

6:

  • 2 where magnocellular RGC axons terminate (large cells) –> one for each eye
  • 4 where parvocellular RGC axons terminate (smaller cells) –> two for each eye, in alteration

Receives some modulation from cortical regions

75
Q

Retinotopic arrangement in LGN

A

Fovea - superior LVN
Peripheral field - inferior
Upper field - lateral
Lower - medial

76
Q

Striate cortex

A

= primary visual cortex/V1, calcarine cortex
Initial stage of cortical processing
Info highly retinotopic (specific for location on retina)
information represented as linear segments/boundaries - cells organized in regular array of orientation columns
Cortical magnification of central vision>peripheral

77
Q

Striate lesions

A

Highly congruous homonymous defects in contralateral hemifield

78
Q

Occipital pole lesion

A

hemi-central scotoma

79
Q

None-occipital pole lesion consequence

A

Macula-sparing hemianopia

80
Q

Superior bank lesion

A

inferior quadrantanopia

81
Q

Inferior bank lesion

A

superior quadrantanopia

82
Q

Extra-striate cortex

A

visual information fans into parallel distributed hierarchy of specialized modules beyond V1
less concerned with retinotopic location; more concerned with specific stimuli
2 streams

83
Q

Dorsal (occipital-parietal) stream

A 
"where" stream
motion processing (v5)
stereopsis
saccadic targeting
manual reaching
depth perception
eye and hand movements
84
Q

Ventral (occipito-temporal) stream

A 
"what" stream
colour processing (V4)
object recognition (words, faces)
85
Q

Lesions to components in dorsal stream

A

Akkinetopsia - rare
Hemineglect
Astereopsis (no depth perception)
Balint’s syndrome

86
Q

Balint’s syndrome

A

triad of:
ocular motor apraxia –> poor targeting of eye movements to targets
optic ataxia –> misreaching for visual object
Simultanagnosia –> inability to attend to >1 object at a time

87
Q

Lesions of components in ventral stream

A

Achromatopsia (cerebral loss of colour vision)
General visual object agnosia
Prosopagnosia: impaired recognition of faces
Alexia

6a (26 decks)

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