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294 Cards in this Set
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Overlap paradigm occurs when
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a second target is displayed in the presence of the first target.
With two targets present, the saccadic latency is 200 msec Latency is thought to be due to the greater effort required to release visual attention from one target when two are presented simultaneously |
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With two targets present, as in with Overlap paradigm, the saccadic latency is
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200 msec
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The Overlap paradigm Latency is thought to be due to the
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greater effort required to release visual attention from one target when two are presented simultaneously
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T/F Gap paradigm has a longer latency than overlap paradigm
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FALSE, its shorter
greater effort required to release visual attention from one target when two are presented simultaneously, which occurs during Overlap paradigm |
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Gap paradigm occurs when
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the first target is extinguished before the second target is displayed.
The saccadic latency is 100 msec The latency is thought to be due to the release of visual attention from fixating at the first target, which enables a saccade to be quickly made to the second target |
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The saccadic latency for gap paradigm is
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100 msec
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The latency for the gap paradigm is thought to be due to the
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release of visual attention from fixating at the first target, which enables a saccade to be quickly made to the second target
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another name for gap paradigm is
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EXPRESS saccade
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T/F longer saccadic latency occuts for dimmer targets
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T
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T/F Shorter saccadic latency occurs for large amplitude saccades
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F
LONGER |
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T/F
Prior knowledge/anticipation of the subject reduces saccadic latency |
T
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The only way to ensure good saccades is by
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PRACTICE --> vision therapy
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What is speed-accuracy tradeoff for saccades?
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LAtency increases if accuracy is desired.
It takes longer to be more accurate. |
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STANDARD saccade latency is usually ~ ______ msec
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200
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Express saccade latency is usually about ~ _____ MSEC
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100
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t/f saccades can be trained
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True
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Acquired ocular motor apraxia is a ___________-- lesion that causes a disorder in voluntary movements. PAteints not able to do ____ eye movements or _____ without head movements. However, VOR and OKN are normal
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bilateral frontoparietal
pursuits saccades |
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T/F Huntington's disease shows a greater increase in the latency for voluntary saccades than for reflexive saccades
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T
disease affects frontal cortex --> affects voluntary saccades |
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What area of the brain affects voluntary saccades?
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frontal cortex
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T/F Vertical saccades are better than horizontal saccades, so you need to test saccades in different directions
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T
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T/F in the Sampled data model of saccade programming, the saccadic path CANNOT be modified
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T
Example: stimulus to the left, then right, then left again. Saccades occurs even though final stimulus is the same as initioal stimulus position. This implies that informaion is sampled in a discrete mater. this reveals the BALLISTIC nature of a saccade |
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What model of programming saccades reveals saccades ballistic nature?
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Sampled data model.
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In the contuous sampling model of saccade programing, programming can be modified up till when?
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70 msec before saccade occurs.
70 msec are required for visual info to travel from retina to the cerebral cortex. |
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Why does it take 70 msec to modify a saccade in the continous sampling model?
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70 msec are required for visual info to travel from retina to the cerebral cortex.
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T/F Both saccade programming models are correct, depending on testing conditions. Both theories also assume the presentations occur within 200 msec of latency time
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T
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Why are we not aware of the visual smear that occurs during a saccade (which causes the eye to rotate)?
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SACCADIC OMISSION --> process that intervenes to prevent blurring of vision
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SACCADIC OMISSION -->
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process that intervenes to prevent blurring of vision
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Saccadic suppression definition
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reduction in isual sensitivity during eye movement so that the visual sstem is less sensitivie to detecting blur during sacades.
Visual threshold increases and sensitivity DECREASES during eye movement |
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Saccadic masking definition
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reduction in ability to detect blur because multiple images are experienced withing a short time creating noise.
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What is the role of saccadic omission in reading?
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Prevents blur and incoherent sentences. 'Reading causse microsaccades, without this saccadic omissions, text is blurry
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The higher visual levels that make the deicions to make a saccade exist where?
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cortex and some midbrain.
Frontal cortex, parietal cortex, thalamus, superior coliculus and basal ganglia. |
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What part of the superior colliculus is important for eye movement?
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VENTRAL portion, gets visual info and sends it to brainstem, premotor neurons for the generation of pulse and step signals.
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Chronic lesions cause slight ___in saccadic latency, slight hypometria, and the inability to make ______ saccades
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increase
express |
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T/F Patients with traumatic brain injuries should expect to have bad saccades in the acute stages with slight recovery when chronic
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T
vision therapy speeds up recovery via nueral regeneration and strengthening |
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What decides to make volitional saccades?
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Frontal cortex!
Volitional saccades are saccades to remembered targets, anticipatory saccades. It is a VERY voluntary type of saccade |
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Volitional saccades are
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saccades to remembered targets, anticipatory saccades.
It is a VERY voluntary type of saccade |
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What provdes the decision to generate saccades to novel stimuli that catches attention?
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PARIETAL cortex, it is responsible for a very REFLEXIVE type of saccade
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What part of the brian is responsible for REFLEXIVE saccades?
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Parietal
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Lesions of the frontal cortex leads to _____ latency, ____ saccades, and ___ predictive tracking
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increased
slowed impaired |
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Lesions of the parietal cortex leads to __________ latency, hypometria, _________ saccade, impaired _________ saccade, and oxcular motor apraxia
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increased
slow predictive |
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Premotor nuerons generate
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pulse and step
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What do excitatory burst neurons generate?
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pulse signal
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What is latency?
What is lead? |
Latency= time between saccade command and saccade occurrence
Lead= te time between firing and saccade occurance |
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Defintion of a long lead excitatory burst neuron=
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bust firing from baseline that occurs soon after saccade command/singal
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defintion of a short lead excitatory burst neuron
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burst fiing from baseline occuring LATER after the saccade command/singal.
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When you saccade to the left the ____ side of the brain as the excitatory burst neuron exited and it sends the excitatory signal to the ______ abducens nucleus and ______ inhibtory burst neuron
The singal is also sent along the abducens internuclear neuron to the _______ brain via the MLF to the ______ oculomotor nucleus |
left side
ipselateral ipselateral Right/contralteral contralateral |
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The energy burst neuron sends a signal to the inhibitory burst neuron which provides inhibition to the _______ abduecens nucleus, and is also sent to the abducenss internuclear neurons to the _______ brain vi MLF to ______ oculomotor nucleus
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contralateral
ispelateral ipselateral |
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Pontomedullary burst neurons are burst neurons for _____ saccades and are located where?
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horizontal
paramedian pontine reticular formation |
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The inhibitory burst nuerons for horizontal saccades are located where?
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rostral medulaa
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T/F A unilateral lesion of the paramedian pontone reticular formation would lead to a deficit of saccades on the contralateral side
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FALSE
ipselateral |
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Burst neurosn for vertical and torsional saccades are loated where?
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rostral interstitual nucleus of the MLF
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T/F A unilateral lesion of the riMLF abolishes unilateral torisonal saccades with only midl effects onvertical saccades
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T
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A _____ lesion of the riMLF abolishes ALL vertical and torsional saccades
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bilateral
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A vertical saccadic palsy is a lesion located in
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the riMLF
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The Niemann-Pick type C disease leads to a defect where?
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riMLF, so patient will have normal horizontal saccades and good VOR, but bad torsional and vertical saccades
Note: see patient have a impaired vertical saccade that has a curved trajectory |
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The higher visual levels that make the deicions to make a saccade exist where?
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cortex and some midbrain.
Frontal cortex, parietal cortex, thalamus, superior coliculus and basal ganglia. |
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What part of the superior colliculus is important for eye movement?
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VENTRAL portion, gets visual info and sends it to brainstem, premotor neurons for the generation of pulse and step signals.
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Chronic lesions cause slight ___in saccadic latency, slight hypometria, and the inability to make ______ saccades
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increase
express |
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T/F Patients with traumatic brain injuries should expect to have bad saccades in the acute stages with slight recovery when chronic
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T
vision therapy speeds up recovery via nueral regeneration and strengthening |
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What decides to make volitional saccades?
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Frontal cortex!
Volitional saccades are saccades to remembered targets, anticipatory saccades. It is a VERY voluntary type of saccade |
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Volitional saccades are
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saccades to remembered targets, anticipatory saccades.
It is a VERY voluntary type of saccade |
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What provdes the decision to generate saccades to novel stimuli that catches attention?
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PARIETAL cortex, it is responsible for a very REFLEXIVE type of saccade
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What part of the brian is responsible for REFLEXIVE saccades?
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Parietal
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Lesions of the frontal cortex leads to _____ latency, ____ saccades, and ___ predictive tracking
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increased
slowed impaired |
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Lesions of the parietal cortex leads to __________ latency, hypometria, _________ saccade, impaired _________ saccade, and oxcular motor apraxia
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increased
slow predictive |
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Premotor nuerons generate
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pulse and step
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What do excitatory burst neurons generate?
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pulse signal
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What is latency?
What is lead? |
Latency= time between saccade command and saccade occurrence
Lead= te time between firing and saccade occurance |
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Defintion of a long lead excitatory burst neuron=
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bust firing from baseline that occurs soon after saccade command/singal
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defintion of a short lead excitatory burst neuron
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burst fiing from baseline occuring LATER after the saccade command/singal.
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When you saccade to the left the ____ side of the brain as the excitatory burst neuron exited and it sends the excitatory signal to the ______ abducens nucleus and ______ inhibitory burst neuron
The signal is also sent along the abducens internuclear neuron to the _______ brain via the MLF to the ______ oculomotor nucleus |
ipselateral
ipselateral Right/contralteral Contralateral |
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The energy burst neuron sends a signal to the inhibitory burst neuron which provides inhibition to the _______ abduecens nucleus, and is also sent to the abducenss internuclear neurons to the _______ brain via MLF to ______ oculomotor nucleus
contralateral |
ispelateral
ipselateral |
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Pontomedullary burst neurons are burst neurons for _____ saccades and are located where?
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Horizontal
paramedian pontine reticular formation |
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The inhibitory burst neurons for horizontal saccades are located where?
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rostral medulla
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T/F A unilateral lesion of the paramedian pontine reticular formation would lead to a deficit of saccades on the contralateral side
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FALSE
Ipselateral |
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Burst neurons for vertical and torsional saccades are located where?
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rostral interstitial nucleus of the MLF
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T/F A unilateral lesion of the riMLF abolishes unilateral torisonal saccades with only mild effects on vertical saccades
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T
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A _____ lesion of the riMLF abolishes ALL vertical and torsional saccades
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Bilateral
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A vertical saccadic palsy is a lesion located in
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the riMLF
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The Niemann-Pick type C disease leads to a defect where?
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riMLF, so patient will have normal horizontal saccades and good VOR, but bad torsional and vertical saccades
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Tonic neurosn are responsible for carrying the _____- signal
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step
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For horizontal movements, the nueral integrators for the step signal are at the
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nucleus prepositus hypoglossi and the medial vestibular nucleus
Neural integrators tegrates burst signal to step signal |
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For vertical and torsional movements, the neural integrator is at the
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interstitial nucleus of cajal
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Pause neurons definition
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neurons that discharge in the absencoe saccades but STOP discharing before and during a saccade.
It is a gate keeper function. ONly after the pause neurons are inhibited can burst neurosn be activated to produce pulse signal for a saccade |
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T/F pause neurons stop firing during blinking
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True!!
Patients with the inability to make saccade resot to blinking to FACILITATE a saccade. Seen with aquired ocular motor apraxia |
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Pause neurons are located in
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the nucleus raphe interpositius..
Lesions here lead to saccadic intrusions and inappropriate saccades |
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Oppsoclonus or Dancing Eye syndrome
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Patients cannot fixate and eyes never stop moving, even when closed.
Aquired wil lbe less dramatic movements since lesion is beningn and usually rsolves. |
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_______ plays a role in the control of saccadic accuracy, the dynamics and initation of sacades, and saccadic adaptation
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Cerebellum
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Wht calibrates saccadic amplitude
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dorsal vermis and fastigial nucleus.
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What calibrates the saccadic pulse-step match?
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flocculus
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Volitional saccade is a saccade to a
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remembered location, to command
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Reflexvice saccade is a saccad t oa
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novel stimulus
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T/F When you undergo vision therapy, you are training eye muscles to move better
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FALSE
you are training accomodation, convergence or visual memory but NOT eye muscles |
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A ________ is an eye movement generated to follow or track a moving taret
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pursuit
Pursuits are absent in afoveated animals, and OKN is intitated instead |
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The stimulus to a pursuit is
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movement
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While during regualr eye movements, the fovea is normally used to track moving targets but under SCOTOPIC conditions (dark), the _________ region has higher acuity and tracts the target instead
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parafoveal
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Can a patient with AMD purse a moving target?
Can patient experience OKN and VOR? |
YES, but accuracy may be compromised an eccentric viewing technique is developed.
Yes to both OKN and VOR. OKN is present due to the wide field of motion and VOR is stimulated by vestibular and NOT visual targes. |
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T/F Pursuits are used for reading
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FALSE, reading involves saccadic eye movements
BOARDS question |
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Pursuit latency
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100-150 msec
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OKN latency
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70 msec
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VOR latency
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16 msec
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Saccade latency
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200 msec
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Ramp target stimulus latency
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100 msec latency
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Ramp target stimulus involves
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movement as a function of time. As eye begins to move, there is a pursuit that LAGS behind and is corrected by a catch-up saccade. The pursuit then becomes accurae and the target and eye movement coincides.
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As eye begins to move, there is a pursuit that _______ behind and is corrected by a _________ saccade.
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LAGS
catch-up The pursuit then becomes accurae and the target and eye movement coincides. |
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Step-ramp target stimulus latency
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150 msec
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Step-ramp target stimulus involves
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movement as a function of time that shows a quick step in 1 direction folloewd by a ramp in the opposite direction.
Patient is tested with a small movement target opposite of the tet direction. As the eye moves there is a pursuit that becomes increasingly accurate as the target and ee movemens coinsice. |
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the ___________ is the first 100 msec of the pursuit movement. With a ______ target, it is contaiminated by a saccade. With a ____ target, it is a pure moement that is uninfluenced by extermnal stimuli
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open loop
ramp step-ramp |
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T/F The open loop system is one that does not recieve feedback to modify its performance
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T
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T/F the open loop pursuit can be moedified by extraneous fators, such as target brightness
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FALSE
CANNOT be modified |
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The pursuit behavior reflects the __ property of the prusuit system
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Intrinsic
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Where the targetand eye movement coincide we have a _____ loop
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closed
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T/F the closed loop system is one which is able to receive feedback to modify its performance
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true
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T/F The closed loop pursuit cannot be modified by extraneous factors
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FALSE
Factorsl ike attention, types of targets, prescence of other cues in the background |
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Stimuli that rigger a pursuit
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visual targets
nonvisual targets (auditory, tactile) Imaginary targets (an illusion of target motion) |
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Definition of anticipatory drifts
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eye movements that occurs befure the onset of a predictable target motion.
If lesion occurs in frontal cortex, you may not be able to perform this pursuit |
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T/F Persuit gain is REDUCED for a target moving in an unpredictable path
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True
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T/F Open loop pursuits are accurate due to feedback
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FALSE
Closed loops |
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T/F Pursuits of a predictable target is SUPERIOR to that of an unprectiable target. HOWEVER, Pursuit gain of a predictable target does show individual difference
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T
it normally varies between .8 to 1.0 for stimulus velocity up to 100 deg/sec. Up to 40 deg/sec--> nice and smooth beteen 40-100 deg/sec --> saccadic intrusion About 100 deg/sec -> jerky saccadic pursuit, cogwheel saccade |
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What is the pursuit gain normally around for stimulus up to 100 degrees?
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.8-1.0
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Up to 40 deg/ sec the pursuit is
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nice and smooth
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between 40-100 deg/sec the pursuit has
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saccadic intrusion
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above 100 degs/sec the pursuit has a
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jerky saccadic pursuit
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Saccadic intrustion occurs when
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the pursiot target is moving too fast or in an unpredictable path. The pursuit gain is reduced
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How do you overcome saccadic intrusion?
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catch-up saccades!!
Also known as error-correcting saddaces |
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What is an error correcting saccade in the backward direction?
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When pursuit gain is too high, gain >1, a BACKUP saccade occurs.
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What happens when you have a bad pursuit, or a gain not equal or 1?
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Visual smearing, consequences of blurred vision and saccadic intrusion
However, pursuits can be trained |
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Motion information for a pursuit is sent from where?
Where does it go? |
striate cortex
Goes to Middle temporal, medial superior temporal, and posterior parietal cerebral cortex visual areas |
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Motion information for a pursuit concerned mainly with predictive tracking is sent from where?
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frontal cortex
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What do pursuit generators generate?
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PULSE and step signals
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Name Pursuit generators that generator step and pulse signals
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Dorsolateral pontine nuclei
AOS (accessory optic system) NOT ( nucleus of optic tract) (AOS and NOT are involved in OKN, which is what pursuits evolved from. These ACTIVATE transcortical pontine cerebellar pursuit pathway) |
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________ is important for adaption changes to make eye movements more accurate
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Cerebellum
particarlly the flocculus and dorsal vermis of the cerebellum, which SYNTHESIZE the pursuit signal. |
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What synthesizes the pursuit signal?
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Flocculus and dorsal vermis of the crebellum
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Horizontal eye movement integrators are
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medial vestibular nucleus and nucleus preopsitius hpoglossi
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The integrator for vertical and torsional pursuits is
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interstitial nucleus if cajal
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If you have a unilateral lesion of the primary visual cortex then
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UNILATERAL lesion affects the CONTRALATERAL field
patient has NO vision and NO pursuit |
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If you have a unilateral lesion of the Middle temporal then
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UNILATERAL lesion affects the CONTRALATERAL field
The patient does NOT see or PERCEIVE motion well NOT able to make pursuits in either direction |
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If you lesion the medial superior temporal then
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it defects motion to the ISILATERAL side over the ENTIRE visual field.
A unilateral lesion impairs pursuits for targets moving towards the side of the lesion |
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What lesion results in an ipselateral defect in pursuits?
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medial superior temporal
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If you lesion the posterior parietal cortex then
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you have a CONTRALATERAL inattention. The exition of the ipselateral visual field. This suggests that the role of the PP involves an attentive target selection
A unilateral lesion leads to IMPAIRED pursuits for targets moving to the side of the lesion!! |
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Bilateral lesions lead to
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bilateral defects in pursuits
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A lesion of the dorsolateral pontine nucleus we see
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a unilateral lesion leads to an ipsilateral defect in pursuits
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A lesion of the flocculus paraflocculus and vermis cause
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provlems with pursuit gain.
Involved in the generation of mainly pulse, but also step A unilateral lesion causes ipsilateral pursuit deficits. |
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T/F A cerebellectomy abolishes all pursuits
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T
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While patient is peforming pursuits we look for
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corrective saccades
catc-up saccades when pursuit gain <1 Backup saccades when pursuit gain is <1 |
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T/F Patients should be able to track targets due to cancellation of VOR response.
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True
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What is the center of horizontal conjugate eye movements?
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ABDUCENS nucleus
it receives input for pursuits, saccade, VOR, and OKN |
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Abudcens muscle is sent the pulse signal from the excitatory burst signals via the _______ for horizontal saccades
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paramedian pontine reticular formation
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Abudecens nucleus receives inport for step signal from
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nucleus prepositus hypoglossi and medial vestibular nucleus
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Oculomotor and trochlear nuclei recieve input for vertial saccades from
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the rostral interstitual nucleus of the MLF
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Ocular motor and trochlear nuclei receive information for the step signal in vertical saccades by the
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interstitial nucleus of CAJAL
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____ ensures all classes of eye movements and gaze olding are ALIBRATED to provide the clearest vision
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Cerebellum
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What is the Vestibulo-cerebellum important for?
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smooth pursuits,
VOR, steady gaze olding. Gaze holding is impaired with a leaky nueral integrator, which causes the eye to from from a primary position to an eccentric position due to an ill sustained step signal |
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Gaze holding is impaired with a leaky nueral integrator, which causes
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the eye to from from a primary position to an eccentric position due to an ill sustained step signal.
If leaky, the cerebellum tries to help by making adaptation chages in steady gaze. |
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Dorsal vermis and underlying fastigial nucleus are important for programming what eye movement
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accurate saccades and smooth pursuits
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Miniature eye movements are responidble for
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preventing fading of visual images --> Troxler
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Examples of minature eye movements
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tremors, microsaccades, and slow drifts
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Tremors have _ frequncy and _ amplitude
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HIGH (50-100 Hz) frequcnies and LOW (5-20 arc sec) amplitude
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T/F Tremors are correlated in the two eeys
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FALSE, direction of tremor does not need to be the same
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Microsaccades are responisble for
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Correcting for drigts of images away from the point of fixation
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T/F Microsaccades are correleated in the two eyes in time of onset and direction
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TRUE, but may not be correlated in amplitude or conjugate eye movement
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T/F Microsaccades can be supresseed with concentration/attention
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TRUE, but may not be correlated in amplitude or conjugate eye movement
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Slow drifts defintion
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deviates from the point of fixation of about 0.1 deg. Velocity ~ 0.25 deg/sec
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T/F slow drifts can be in opposite directions in the two eyes
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TRUE, which is why microsaccades are not congate
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What is the field-holding reflex?
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When there is an imaginary target, one eye may drift off since stability cannot be mminatained Indicates that visual info is important for maintance of accurate fixation
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The ____ relfex
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indicates that visual info is important for maintaence of accurate fixation
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T/F Fixation is a PURSUIT eye movemetn
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FALSE, pursuits change in veolicty over time, but fixation does not
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T/F Fixation changes in velocity over time
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FALSE
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T/F Pursuits change in velocity over time
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TRUE
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Reading fixation behavior
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The patient have a microsaccade, then a fixation pause and then a step down regression movement
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Scanpaths definition
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Longest fixation duration on releveant information. We do not tend to look at whole pictures but scan specific areas of picture
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2 causes for larger amplitude drifts
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amblyopia and macular scotoma
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What is the stimulus for accomodation?
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BLUR, slightly out of focus
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The amount of accomodation induced depends on
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the CA/C ratio Convergence acommodation/ convergence or the convergence accomodation induced by convergence
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Binocular disparity information is used by the brain to create ______- and to perceive steropsis
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congervence or divergence
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In order to accomdate accurately you need this kind of aberration
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Chromatic. More than 1 wavelength of light is required to control accomodation accuracy
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T/F More than 1 wavelength of light is required to control accomodation accuracy
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True therefore one can accomdate better in white light due to chromatic aberration compared to monochromatic light
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Defintion of tonic accomodation
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the resting state of accomodation due to the tonus of the ciliary muscle
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When is tonic accomodation manifested
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when the stimulus condition is degraded, like in darkness. This is why we see induced myopia seen in pilots and night driving
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Tonic accomodation range ______D
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.5 to 1.5 D
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The ______ the lens, the more accomodative position, which causes the image to focus in front of the retina
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THICKER.
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T/F Dark focus wen accommodation is measured in total darkness, it is the RESTING state of accomodation
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T
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What is the MOST important stimulus of accomodation
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REFLEX accomodation, induced to obrain clear focus.
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What clinical test is used to check reflex accomodation
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Flippers +2/-2D to see how fast you can clear an image
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Proximal accomodation is induced by
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awareness of near objects independent of the actual stimulus distance. See this when you use a microscope "instrument myopia. Psychic accommadation is another name for it.
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What is the limiting factor of accommodation
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lens/
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What type of accomodation is stimulated when doing Donder's push up test?
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proximal
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When accomodative stimulus and accomdative response is equal, gain=
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0. Accomdation is accurate and neutralization occurs at the stimulus/target location
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When the accommodative response is less than the accommodative stimulus, there is an accomodation _____ and neutralization is behind the target
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LAG
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When the accommodative response is greaterthan the accommodative stimulus, there is an accomodation _____ and neutralization is in front of the target
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LEAD
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Linear accomodation lag is normally about ______ to _____ D
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normally about +.25D to + . 75D
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When the demand of lag becomes larger, the system becomes less efficient and is known as
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soft saturation
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Amplitude of accomodation is equal to
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Hard saturation
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What is an accurate accomodation response?
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When gain=1 or when the lag of accomodation is SMALL
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T/F those that study or read often tend to have lead of accomodation rather than a lag
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TRUE
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How does spatial frequency affect accomodation response
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accomodation is MOST accurate between 3-10 cydles/deg/ Anything below 1 cy/deg and above 25 cycle/deg is considered abnormal
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T/F Accomodation resonse is less accurate with high contrast stimuli
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FALSE MORE accurate. With low contrast, accomodation lag INCREASES
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With low contrast levels, accomodation lag _______-
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increases
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T/F Accomodation response is better with high luminance
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T
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T/F Accomodation response reduces when the stimulation is peripheral
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True. 10 degrees of eccentricity results in NO accomodative response
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Why does a strabismic patient accommodate poorly ?
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Accomodation accuracy is dependent on retinal location which is not at the fovea for stabs. See more lag.
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What is the accomodation aftereffect?
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It is the tendency of accomodation to remain at a previous stimulus level. It is known as a ccomodation adaption. Prolonged near point viewing induces prolonged accomodation aftereffects.
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Accomdation latency is
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380 msec + or - 80. it is a SLOW system. Entire response takes about ~1 sec.
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T/F accomodation is easily trained
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TRUE
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What is the near response triad?
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Accomodation, convergence, and misosis
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When ________ is large, vergence is inaccurae
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Fusional Disparaity
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Disparity divergence less than desired fixation plan results in an _______ error
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Eso fusional disparaity. Eyes experience more disparity as they diverge so eyes like to stay converged
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Disparity convergence less than desired fixation plan results in an ____ erro
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Exo fusional disparity. Get more disparity when eyes converge so eyes like to stay diverged.
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Vergence induces accomodation through the _______link and Accomodation induces vergence by way of the ______ link
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1.CA/C link 2. AC/A link
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Minus lenses induce _________ and increase _________ vergence results in eso Fusional disparity
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accomodation and increase accomodative vergence
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Plus lenses relax ___- and __________ vergence resulting in exo fusional disparity
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accomodation and accomodative vergence.
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Possible test question: PLUS lenses shirt t he forced duction dixation disparity curve ___- and minus lenses shift curve _______
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DOWN (more exo) for plus and UP(more eso) for minus lenses
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When you combine the prism and lens cruve you obtain the ___- which provides a measure of associated AC/A
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Derived curve. The slop measure associated AC/A, which is a binocular measurement
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Prism adaptation causes a ________ in fixation disparity with prolonged viewing duration. This makes vergence more accurate and less stressed
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reduction
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Type II curve shows that there is better adaptability for _______ during Vision therapy
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BO than BI. Type 2 curves have a LOW fusional disparity for BO prisms, which means better adaptability. Patients tend to be more eso
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TYPE III curve shows that there is better adaptabiltiy for _____ during vision therapy
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BI than BO. Type 3 curves have LOW fusional disparity for BI prisms
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PRC/NRC positive relative covergence/ negative relative convergence tested
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when patient says blur
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PFR/NFR positive fusional reserve/negative fusional reserve tested
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when patient says blur-break. Maximum value of accommodative vergence
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When patient "recovers" from a blur-break test, it tests
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efficiency of the vergence system to recover from diplopia and take up bixfixation again.
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Definition of fixation disparity
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accuracy of vergence during active binocular vision.
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Vergence facility definition
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How fast you can change vergence between two distances without getting fatigued
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Prism adaptation ability defition
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ability to modify your vergence system to reduce stress.
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Using maddox rod you can test
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tonic, promixal, accomodative and disparity vergence
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T/F using a maddox rod you can test voluntary vergence
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FALSE, but you can test tonic, promiximal, accomodative and disparity vergences
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T/F a FAST fusional vergence is stimulated by binocular disparity
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TRUE. It is stressful to the vergence system
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Prism adaptation allows the conversion of __- fusional vergence to _ fusional vergence
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FAST to SLOW
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T/F Prism adaptation allows the conversion of fast fusional vergences to slow fusional vergences
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TRUE
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If more fast relfex accomodation is converted throu accomodation adaption to slow, then _ is lowered
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AC/A
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You have a HIGH AC/A level with _ accomodative adaption
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LOW
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You have a LOW AC/A with _____ accomodative adaption
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HIGH
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You hae HIGH CA/C with _____- prism adaption
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LOW
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You have LOW CA/C with ______ prism adaption
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HIGH
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Patient with high AC/C experience ______--
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eye strain
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Passive treatment management of binocular motor disorders
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lenses (used first) and prisms used later to relieve stress, to remove symptoms, and neutralize te deviations
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Active treatment for binocular motor disorders
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vision therapy to recalibrate abnormalities to normalize prism adaptation.
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What decides to make a vergence movement
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cerebral cortex
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Near cells definition
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activated when target is close. Cells involved in vergence dcision
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Far cells definition
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activated when the target is far away. Inolved in vergence decisions.
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Size coding cells:
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recognize the change in size of an object.
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Brainstem vergen generator is located ________ and generates _______-
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in the mesencephalic reticular formation. Generates pulse and step signals.
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T/F premotor convergence and divergence cells are distinct cell populations
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TRUE
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T/F there are more convergence nuerons divergences neurons
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TRUE
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Vergence tonic cells=
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carry step/position signal
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Vergence burst cells=
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pulse/elocity signal
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Vergence burst-tonic cells=
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carry step and pulse signals
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Saccadic-like vergence
|
refers to quick changes and maintenance of the vergence anglel
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pursuit like vergence
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refers to slow changes in the vergence angle due to smooth tracking of the target depth. Seen when doing NPC testing
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A _ deficit is manifested as misaligment in the visual axes of the two eyes
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Motor
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A ___ deficit is manigested as localized suppresion where the brain shuts off the bad eye
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sensory. NO DISPARITY vergence is initated, and only accomodative vergence is used instead.
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Convergence retraction nystagmus
|
a SACCADIC diorder due to lesion in rostral midbrain. Seen more obviously with with upward saccades
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Duane's Retraction
|
Duane's retraction syndrome (DRS) is a congenital disorder of ocular motility characterized by lim ited abduction, adduction or both. Retraction due to co-contraction of MR and Lr. Cmmon innervation from CN 3
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Whipple diagnosis
|
Observe pendular oscullation nystagmus with inability to make outward saccade
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Antisaccades are
|
geresponse to instructions to do so in the labnerated to an opposite direction from the target. Usually made in
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REM is a ______ saccade
|
involuntary
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Velocity-Amplitude relationship for saccades: the __ the amplitude of the eye movement, the greater is the peak velocity of the movement
|
LARGER/
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Ampltiude-Duration relationship for saccades: the time course taken to complete a saccade is _____- dependent on the amplitdue of the movement
|
LINEAR. HOWEVER, linearity may break down if the saccade amplitude is about 50 deg or larger
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Under natural conditions, 85% of our most frequent saccadic eye movements amplitdues fall below _ degrees
|
15
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|
|
Factors that influence saccadic accuracy inslude
|
Size, Luminance of target. Tiredness of subject, and Age. SALT
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Statis overshout or undershoot of a saccade is due to a ______ error and to correct it, you make a
|
Step size error, you use a corrective saccade
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|
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A glissadic ovvershoot or undershoot of a saccade is ude to a _____ error and a corrective measure is a
|
pulse-step mismatch. You glissade
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|
|
Static dymetria is due to
|
an inaccuracy in the step command, where the step signal to EOM to maintain eye position at a certain location is not the same as the desired location.
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|
|
Hypometria of saccades occurs when the saccide is _ directed towards peripher, when it is ____ in amplitude and if its made in the presence of ____.
|
centifugally, large, nontarget
|
|
|
Glassidic dymetria occurs when
|
the desired position of the eye is correctly defined by the STEP component, but t he PULSE compent does not bring the eye to this position. After termination of pulse, the eye creeps slowly and expoentially to the desired position. Time constant of 100-200 msec
|
|
|
T/F Static dysmetria is a problem with STEP and Glassidic dymetria is a problem with PULSE
|
|
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|
Saccade is ballistic in nature implying that
|
once the decision to generate a saccade is made, its amplitude and velocity calculated, nothing can change the course of the saccadic eye movement
|
|
|
Why do you have 70 msec to modify your saccade
|
it’s the time it takes for visual info to travel from retina to central visual pathways and motor system in brain stem
|
|
|
Lesion studies of superior colliculus show that chronic lesions cause what kind of defects ins saccadic eye movements
|
subtle ut specfic defects where latency is increased and accuracy is impaired. Also decreass ability to geenrate express saccades
|
|
|
Lesion studies of superior colliculus show that acute lesions cause what kind of saccadic deficits?
|
pround. Delayed in initation, decrease in amplitude, abnormal in direction and decreased in speed
|
|
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T/F control of saccades are by the frontal and parietal cortices appears to be via 2 parallel descending pathways
|
true.
|
|
|
What is involved in the generation of voluntary saccades and in the suppression of reflex saccades?
|
Thalamus and Basal ganglia
|
|
|
Where are pause neurons found?
|
nucleus raphe interpositius. Stimulation of pause neurons cause inability of the monkey to make saccades or generate quick phases in any direction/
|
|
|
Catch-up/error saccades occur whenever
|
smooth prusiot componenet failts to track the target correctly (when gain is reduced)
|
|
|
Aberrant tremors reflect the functional state of the
|
brainstem. It is correlated with the depth of death
|
|
|
Square-wave jerk:
|
movement that carriers the fovea away from the object of regard via a saccade and the nreturns the eye back to the origional position by a second oppositely directed saccade.
|
|
|
Macro square-wave jerk:
|
is a variation of square wave jerk with larger amplitude, occurs more frequently and is found in multiple of sclerosis
|
|
|
This type of saccadic intrustion is characterized by a sequence of saccades of increaseing and then decreasing amplitude to either side of the fixation point
|
macrosaccadic oscillations
|
|
|
This type of nystagmus shows velocity of movement similar in BOTH directions. The congenital type is tpically horizontal amd os asspcoated woth ab;inism. The acquired type may be found in MS
|
pendular
|
|
|
This nystagmus has slow phase that moves the eye away from the object with increasing velocity, followed by a saccade to correct this error and regain position.
|
Congenital jerk nystagmus
|
|
|
This nystagmus hasa slo phase which moves the eye awy from gaze towards the midline with DECREASING velocity, then saccades to corect the position error. Seen in cerebellar and vesibular problems
|
gaze evoked nystagmus
|
|
|
T/F an increase in accomodation can induce the eyes to converge and an increase in convegence can induc the eyes to accommodate
|
TRUE
|
|
|
If you occlude OS and blur OD, OD will accomdate and OS will start to make a vergence movement, this is reffered to as
|
accomodative vergence
|
|
|
To assess te vergence accomodation interaction, we use the ________ ratio
|
AC/A. The amplitude of convergence brought by 1 D change in accomodation
|
|
|
The AC/A ratio is stypically
|
3-4 diopters
|
|
|
T/F The efferent pathway for accomodation is the sympathetic innervation to the ciliary muscle
|
FALSE, parasympathetic!!
|
|
|
T/F the efferent pathway to relax accomodation is the sympathetic pathway innervation
|
TRUE
|
|
|
________ vergence is said to be due to the balance of intrinsic convergence and divergence innervations to the EOM
|
tonic
|
|
|
____ phoria is the phoria obtained when fixation disparity is reduced to zero by addidng prisms
|
Associated phoria. This is a binocular phenomenon
|
|
|
T/F The response of vergence to prism is slightly LESS than the stimulus ampltiude so that the response lags the stimulus
|
True Lag of convergence is exofixation disparity and lag of divergence is esofixation disparity
|
|
|
Type 1 fixation graph
|
amplitude of FD increases equally in reponse to both divergent and convergent stimuli. Person takes BI and BO prism equally
|
|
|
Type 2 fixation graph
|
Person has a harder time with BO prisms then BI prisms
|
|
|
Type 3 fixation graph
|
Person has a harder time with BI prism then with BO
|
|
|
Type 4 fixation graph
|
Magnitude of fusional disparity remains nearly constant despite BI or BO stimuli. Person tends to have abnormal binocular vision
|
|
|
What relieves the stress from the accommodative system?
|
accomodative adaptation
|
|
|
What relieve stress fri from the vergence system?
|
prism adaptation
|
