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Eye Flashcards

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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
Vergence system
occipital-parietal to midbrain pre-tectum | slow disconjugate eye movements
26
Non-optic reflex system
Oculocephalic reflex caloric responses Slow eye movements Brainstem vestibular system
27
Frontal gaze palsy
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
28
Progressive supranuclear palsy (PSP)
``` gradual impairment of supranuclear gaze Vertical > horizontal Voluntary > pursuit > reflex relatively preserved vertical movements in non-optic reflexes axial dystonia dementia no convergence ```
29
Perinaud's syndrome
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
30
Intranuclear ophthalmoplegia
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
31
Complete CN III palsy SSx
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
32
CN III palsy cause
internal carotid artery aneurysm a common cause
33
CN VI palsy
horizontal diplopia | some patinets may tend to turn head toward affected eye to compensate
34
Choroid
vascular dark brown membrane (with melanin) | reduces light scatter within the eye
35
Ciliary body
ring of SM control eye movement via suspensory ligament | focusing vision
36
Outer pigmented layer (RPE) of the retina
absorbs light and prevents light scatter | role in photoreceptor regeneration
37
Inner neural layer of the retina
contains photoreceptors and neurons
38
Uveitis
more serious often associated with systemic disease (autoimmune, infections, etc) can be segmental
39
Blood supply to the eye
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
Anterior ischemic optic neuropathy
due to ischemia in posterior ciliary arteries | see swollen infarcted optic disc, greyish
41
Central retinal artery occlusion
pale retina with a cherry red spot at fovea from shine-through of choroid little inner retina at fovea
42
Rods
provide scotopic vision (dim light) - high sensitivity in the dark Low spatial resolution - summation to one bipolar cell Rhodopsin pigment
43
Cones
provide photopic vision (bright light) colour vision - reflects type of opsin; R, G, B X-chromosome High resolution central vision
44
Photopigment
opsin + retinal
45
Phototransduction cascade
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
Photoreceptor distribution
Fovea: no rods, just cones Rods highest density at 20 degrees eccentricity Rods/cones decline in density with increasing eccentricity
47
Physiologic blind spot
at the optic disc Retinal ganglion cells gather to form optic nerve no photoreceptors
48
Cone dystrophy/macular degeneration
central scotoma with poor central daytime vision
49
Retinitis pigmentosa
disease of rods | causes ring scotomata and nyctalopia (night blindness)
50
Bipolar cell - relay
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
OFF bipolar cells
active without light, excited by glutamate
52
ON bipolar cells
active with light, inhibited by glutamate (light reduces glutamate release)
53
Modulation of bipolar cells
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
Parvocellular retinal ganglion cells
``` small cell bodies short dendrites small receptive fields sustained response to onset of light --> high spatial resolution, low temporal resolution ``` colour opponency
55
Magnocellular retinal ganglion cells
large cell bodies long dendrites large receptive fields respond transiently to onset/offset of light --> low spatial resolution, high temporal resolution
56
Papillomacular bundle
large bundle of RGC axons from fovea and macula
57
Temporal raphe
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
RGC fibers from nasal retina
temporal visual field | head straight to the optic disc
59
Central scotoma
optic neuritis | info from fovea --> disc all gone
60
Ceco-central scotoma
lesion closer to blind spot | hole contains lesion + blind spot
61
Nasal arcuate defect
inferior/superior reversed lesion in arching fibers e.g. glaucoma
62
Temporal wedge defect
on the other side of the blind spot | rare
63
Optic nerve
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
Optic tract
continuation from optic chiasm contains information from the contralateral hemifield of each eye terminates in LGN
65
Pretectal nuclei
midbrain | pupil light reflex
66
Superior colliculus (vision)
rapid eye/head orientation | reflexive eye movements
67
Nucleus of optic tract/accessory optic system
supplement vestibular information in keeping gaze stable
68
Suprachiastmatic nuclei
hypothalamus | diurnal regulation of homeostasis
69
Lesions of optic chiasm
Bitemporal hemianopia almost always due to mass effect, often a pituitary tumour loss of nasal retinal fibers from both eyes
70
Lesions of optic tract
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
Lesion to the Meyer loop
Contralateral superior quadrantanopia | fibers from upper portion of the contralateral visual field from both eyes
72
Lesion to the optic radiations
Contralateral inferior quadrantanopia
73
Lesion to the primary visual cortex
Contralateral homonymous hemianopia | loss of visual info from contralateral visual field
74
LGN layers
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
Retinotopic arrangement in LGN
Fovea - superior LVN Peripheral field - inferior Upper field - lateral Lower - medial
76
Striate cortex
= 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
Striate lesions
Highly congruous homonymous defects in contralateral hemifield
78
Occipital pole lesion
hemi-central scotoma
79
None-occipital pole lesion consequence
Macula-sparing hemianopia
80
Superior bank lesion
inferior quadrantanopia
81
Inferior bank lesion
superior quadrantanopia
82
Extra-striate cortex
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
Dorsal (occipital-parietal) stream
``` "where" stream motion processing (v5) stereopsis saccadic targeting manual reaching depth perception eye and hand movements ```
84
Ventral (occipito-temporal) stream
``` "what" stream colour processing (V4) object recognition (words, faces) ```
85
Lesions to components in dorsal stream
Akkinetopsia - rare Hemineglect Astereopsis (no depth perception) Balint's syndrome
86
Balint's syndrome
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
Lesions of components in ventral stream
Achromatopsia (cerebral loss of colour vision) General visual object agnosia Prosopagnosia: impaired recognition of faces Alexia

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