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56 Cards in this Set
- Front
- Back
Broadly, what are the three parts of the visual pathway?
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Optical
Retinocortical Perceptual |
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What is the upper part of the perceptual pathway responsible for?
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Visuospatial processing
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What is the lower part of the perceptual pathway responsible for?
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Recgnition
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What are some of the clinical manifestations of the retinocortical disorders?
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Blurred vision
Dim vision Scotomas Light spots |
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What is a cause of dim vision?
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In general, less traffic through the retinocortical system
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What is a cause of scotoma?
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Lesion in a part of the retinocortical pathway
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What is a clinical manifestation of the occiipito-temporal part of the perceptual system?
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Problems with the what: object, color recognition
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What is a clinical manifestation of the occiipito-parietal part of the perceptual system?
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Problems with the where: distributed attention, trouble with spatial relations
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How do you eliminate optical problems when thinking about optical disorders?
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Put pinholes!
It gets rid of media problems, refractive errors, etc. |
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What are two things you should always check if you're evaluating what you think is a retinocortical disorder?
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Pupil reactions
Visual fields |
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What is the pupillary reflex pathway?
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What parts of the midbrain are active in the pupillary reflex pathway?
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Edinger-westphal nucleus
Branchium of the superior colliculus |
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How do you test for a relative afferent pupil defect? Wht do you find?
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Swinging light test
If a pupil expands when there's light, you've got one of two problems: -Defect in that pupil -Bilateral defect, but the one that expands is worse |
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What test do you use to see where a lesion is in the retinocortical pathway?
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Visual fields
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Where are different places on the retinocortical pathway that you can have lesions?
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1. Retinal ganglion cells, optic nerve
2. Optic chiasm 3. Optic tracts, optic radiations, visual cortex |
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Where are some different places in the optic nerve that you can get defext?
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Right eye:
1.Fovea/macula 2.Arcurate 3.Radial (YOU SEE THE TEMPORAL FIELD) |
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What part of the vision is lost in a central scotoma? Where does this lesion take place?
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You get a lesion of all of the fibers from the fovea going into the optic nerve, which leads to a blind spot in the center of vision
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What part of the vision is lost in a cecocentral scotoma? Where does this lesion take place?
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Not only in the fovea, but the other ganglia that extend over are effected
It's a scotoma from the blind spot to the point of vision |
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What part of the vision is lost in an arcuate scotoma? Where does this lesion take place?
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Scimtar with a border along the meridian of sight
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What part of the vision is lost in a temporal scotoma? Where does this lesion take place?
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If this is the RIGHT edge, you're losing the NASAL cells, which means that you're having a defect in the TEMPORAL field of sight
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What happens after the optic chiasm to the visual information?
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The fibers are segregated into hemifields: "right world" goes to left brain, vice versa
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If you've got a defect in the optic chiasm, what will be the effect on the visual field?
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Bitemporal hemianopia: you're losing the sight of the nasal fibers, which are the ones that cross.
This results in an inability to see the TEMPORAL fields |
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If you have a visual field defect in he retrochiasma, what will be the effect on visual fields?
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Homonymous hemianopia - this could be a defect anywhere past the chiasm
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How do you want to go about evaluating the perceptual disorders of the visual system?
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See if they can identify "what" (temporal)
See if they can identify the "where"/spatial (parietal lobe) |
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What are the different types of eye movements performed by the ocular motor system?
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Saccades
Pursuit Vergence Vestibulo-ocular |
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What is the function of a saccade? What is unique about it?
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Move the eyes from one equidistant target to another
You don't see anything between the two points! |
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What is the function of a pursuit?
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Keep the eyes on a target when the target moves
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What is the function of a vergence?
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Keep the eyes on a target as the distance from the viewer changes
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What is the function of a vestibulo-ocular eye movements?
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Keep the eyes on the target when the viewer's head moves
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What are the two types of saccades?
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Voluntary
Invountary |
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What are some of the voluntary saccades?
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Move the eyes to a target seen in a peripheral field
Move the eyes to an unseen target |
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What are some of the involuntary saccades/
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REM
Fast phases of nystagmus Random |
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In general, where does the control of involuntary horizontal saccades take place?
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Front of the brain
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In general, where does the control of voluntary horizontal saccades take place?
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Back of the brain
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What is the signalling pathway for the control of horizontal saccades?
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1. Signal comes in from PPRF
2. Synapse in the CNVInucleus 3.2 signals sent out: -Lateral rectus -Interneuron to the CNIII nucleus through the MLF Moving the eyes SIgnalling is ipsilateral once you get to hte pons |
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In general, how are vertical saccades controlled?
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Bihemispheric
One group of pathways for upgaze, another for downgaze |
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What pathways are involved in the control of vertical saccades?
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What are some of the different disorders of saccade?
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Absent (gaze palsy)
Reduced amplitude (hypometric) Slow Inaccurate (dysmetric) Intrusive |
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Where is pursuit generated in the brain?
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Occipito-parietal region
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In order to perform pursuit eye movements, what is a precondition?
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You've got to be able to see first!
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What are the pathways involved in the control of horizontal pursuit?
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The posterior part of the brain dominates
The final common pathway is the CNVI nucleus Cerebellum is also involved. |
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How do you evaluate pursuit?
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Have the patient follow your moving light/finger
Is it smooth? Is it complete? Are there oscillations? |
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If a patient is unable to pursue, what will you see?
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They'll be able to follow your finger for a while, stop, and then have to perform a catchup saccade
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What are various causes of problems with pursuit?
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Lack of sleep
Alcohol intoxication Pursuit is quick to go, as far as eye movements go |
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What are some of the disorders of pursuit?
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Cogwheel
Absent |
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What are the two types of vergent eye movements?
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Convergence: move the eyes closer to one another
Divergence (hard to do): move the eyes farther apart from one another |
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Generally, what are the parts of the brain involved in the vergence pathway?
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Generation in the parieto-occipital regions
Signal travels to the midbrain We don't know, exactly |
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How do you go about evaluating vergence?
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Measure ocular alignment when the eyes are focusing on a distant target, then when they're focusing on a near target
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What are the different disorders of vergent?
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Too much convergence
Too little convergence |
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Where is the vestibulo-ocular reflex generated?
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Labyrinths
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Does the vestibulo-ocular reflex reach the cerebrum?
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No.
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What parts of the brain are involved in the control of the vestibulo-ocular reflex?
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How do you evaluate the vestibulo-ocular reflex?
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It's hard: if people are awake, they make voluntary eye movements
1. Doll's headmaneuver; move head rapidly, look for slow contraversive conjugate eye movements 2. Cold water calorics: look for ipsiversive slow conjugate eye movements and perhaps contraversive involuntary saccades |
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What are some of the vestibulo-ocular disorders?
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If the entire thing is underfunctioning, the entire world looks like it's a hand-held camera: "oscillopsia"
Unilateral: nystagmus |
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What are the features of a supranuclear gaze palsy?
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1. Absent voluntary gaze
2. Intact vestibulo-ocular reflex |
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What are some of the different levels of the visual field pathways?
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Supranuclear: brain cerebral centers to the PPRF
Intranuclear: MLF Nuclear: PPRF, pons |