Term
| Vernal keratoconjunctivitis |
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Definition
| covers the entire superior tarsus and there is often a ropy adherent mucous discharge |
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Term
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Definition
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Term
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Definition
| discharge during steady fixation but not during pursuit of a moving target |
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Term
| The threshold for electrical stimulation of saccades in the |
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Definition
| frontal eye fields and superior colliculus is elevated |
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Term
| Micro stimulation of neurons from where affect the speed of ongoing pursuit but does not pr9duce pursuit if the object of regard is stationary |
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Definition
| medial superior temporal visual area or in the dorsolateral pontine nucleus |
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Term
| How many types of eye movements take place during attempted fixation |
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Definition
| Three: Tremor, Drift, Microsaccade |
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Term
| Average amplititude for tremor |
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Definition
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Term
| Tremor velocity may be as high as |
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Definition
|
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Term
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Definition
| a low velocity movement, typically 1 to 8 min arc per second with a mean of 5 min arc per second (15 cones per second) |
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Term
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Definition
| irregular and of variable low frequency. |
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Term
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Definition
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Term
| Drift makes up more than what percentage of ones total fixation time |
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Definition
|
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Term
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Definition
| have a frequency of occurrency of 1 to 2 per second |
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Term
| Microsaccades or binocular or monocular |
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Definition
| binocular; which suggest that they are under central neurologic control |
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Term
| Drift component is determined |
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Definition
|
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Term
| What is the time constant with the slow leaky neural integrator hypothesis in gaze holding phenomenon |
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Definition
|
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Term
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Definition
| small (miniature) eye movement during attempted fixation) |
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Term
| Spatial localization can be correlated with the duration of fixation generally within a |
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Definition
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Term
| The velocity of drift will determine |
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Definition
| if you have a saccade or drift |
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Term
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Definition
| slow velocity irregular component eye movement (considered to represent smooth pursuit eye movement in response to retinal image slip |
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Term
| Average velocity and range of fixation – drift |
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Definition
| ~5 in arc per sec ~15 cone diameter, range of 1-8 min arc per sec |
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Term
| Amplitude and frequency of drift |
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Definition
|
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Term
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Definition
| producing mechanism but can serve as an error reducing mechanism |
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Term
| Drifts are _____ (not/are) correlated between both eyes. |
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Definition
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Term
| Drifts represent noise of |
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Definition
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Term
| What is average amplitutude, range, and duration of microsaccades |
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Definition
| average amplitude – 5 min arc, range 1-25 min arc, duration 10-25 msec |
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Term
| Peak velocity profile for microsaccade |
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Definition
| typically 1-20 deg/sec that fits the main sequence |
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Term
| In the dark accuracy of fixation is dependent on |
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Definition
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Term
| In order for corrective saccade to be initiated the drift velocity must be |
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Definition
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Term
| Probability of occurrence of a microsaccade increases with |
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Definition
| eccentricity of gaze (100% - 6 min of arc) |
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Term
| Frequency, average amplitude, velocity of Tremor |
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Definition
| High frequency movements typically ranging from 30-100 Hz, average amplitutude – 20 arsec (range 5-30), Velocity of tremor - |
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Term
| How is tremor related to frequency |
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Definition
| inversely proportional. Is not correlated between the two eyes, does not have central origin. It appears to represent a state of incomplete partial tetanus and has No effect on vision. |
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Term
| The most important nuclei for horizontal gaze holding phenomenon are |
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Definition
| NPH (Nucleus Prepositus Hypoglossi) , MVN (Medial Vestibular Nucleus for Horizontal Eye movements), Cerebellar flocculus and posterior vermis |
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Term
| Gaze holding depends upon connection between |
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Definition
| brainstem nuclei (NPH, MVN for horizontal movements and interstitial nucleus of cajal for vertical movements) and the cerebellum |
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Term
| The role of the Neural integrator |
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Definition
| is to convert phasic velocity commands encoded in the saccadic, vestibular optokinetic or pursuit systems into step position commands, causing tonic contractions of the extraocular muscles. |
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Term
| Microsaccades are caused by |
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Definition
| drifts (to move the fixation back on the original position) |
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Term
| How does the brainstem encode signals |
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Definition
| 1. The discharge frequency of an ocular motor neuron is linearly proportional to eye position during fixation 2.Ocular motor neurons modulate their discharge in proportion to eye velocity. 3. Combined velocity and position signals are necessary to compensate for the restrictions imposed upon the eye by the mechanical properties of the orbital contents: A) Viscous drag slows down eye movements B) Elastic-restoring forces pull the eye back towards primary position. |
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Term
| The neurologic substrate involved in neural integrating and related gaze holding function consist of the nucleus |
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Definition
| prepositus hypoglossi and medial vestibular nucleus for horizontal conjugate movements and probably the interstitial nucleus of Caja for vertical conjugate movements |
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Term
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Definition
| when there is a leaky integrator. An imperfection. |
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