Vision science 3 final
what do lesions in the vermis cause?4
-esodeviation -varying alignment with orbital position -disconjugacy of saccades -problems with phoria adaptation
What happens to the lens with age? with thickness, ability to change shape, and ability to constrict ciliary muscle
-increase thickness -decrease ability to change shape -remain the same for constriction of ciliary muscle
what are other symptoms to look for when someone has horners syndrome?
-mild ptosis -increase in accomm amplitude -facial anhydrosis (lack of sweating)
how many hz and deg of amp are slow oscillatory movements?
0.04-0.1 hz 0.1-0.2 deg in amp
How much does the lens thicken during accommodation?
0.5 mm
what is the true statemtent regarding Vestibular OK interaction? none velocity storage only OKN and rotary opposite movements OKAN and post rotary nystag in the same directions
NONE
Does pendular nystagmus have fast and slow phases?
No
Is all nystagmus abnormal ?
No
Is there oscillopsia with Congenital nystagmus?
No
What is rebound nystagmus ?
Nystagmus at central gaze after prolonged eccentric fixation
What is rebound nystagmus?
Nystagmus at central gaze following prolonged eccentric fixation
What is Alexanders law and does periph vestibular nystagmus obey it?
Nystagmus in increased in the direction of the quick phases Quick=larger
What is end point nystagmus?
Nystagmus occurring in extreme lateral gaze / eccentric gaze
what other nucleus is the edinger-westphal nucleus next to?
OMN
What are the kinds of physiological nystagmus ?
Okn an okan Vestibular nystagmus and vestibular after nystagmus End point nystagmus Rebound nystagmus
How many planes is pathological nystagmus in?
One or more
What directions Are the fast and slow phases going in? Same or opposite
Opposite
What can also come with pathological nystagmus
Oscillopsia
What else comes with acquired pendular nystagmus?
Oscillopsia
T/F reflex blinks can be conditioned with a noise and a puff of air
True get sound and will blink wont even need air anymore
While medulla, pontine, and midbrain lesions are associated with what type of nystagmus?
Up beat
What are the types of beating that can happen with central vestibular nystagmus?
Up beat Down beat Or torsional Or any combination
what must be negated during an initial head movement but must switch back on upon reaching the gaze goal?
VOR
What if the pathological vestibular nystagmus is central in origin? It indicates that there is dysfunction in what?
VOR pathway Including vestibulocerebellum or brainstem VOR structures
what are combined head and eye tracking and tracking a head-fixed target an example of?
VOR-SP interaction
What is another feature that is a distinguishing feature of nystagmus?
Velocity of the slow phase
What happens in periodic alternating nystagmus?
Vestibular nystagmus where the direction changes every 90-120 sec
What kind of nystagmus shows a linear slow phase?
Vestibular nysyagmus
_________-____________ is most often implicated in downbeat nystagmus
Vestibular-cerebellum
Does central vestibular nystagmus obey alexanders law?
Yes - nystagmus in increased toward the side with the quick phases
why is there so much research going into the IOLs?
ability to constrict ciliary muscle remains the same
if you want perfect yoking, what should equal what?
ac/a=pupillary distance
what does binocular viewing improve?
accomdation- cross linking conv and accomm
The subject must engage in what kind of mechanisms to clear up the blur?
accommodation
What is necessary for changing focus on viewing a near object?
accommodation
cells encoding vergence in more central areas such as the cerebellum, brainstem, and cortex also appear to encode what?
accommodation
stimulation of a local region of the EW nucleus can produce what without pupil constriction?
accommodation
The EW nucleus and ciliary ganglion are important structures for which of the following functions?
accommodation and pupil control
What happens to accommodation during presbyopia (aging)?
accommodation capability reduces continuously through life
what happens in myopes with accommodation?
accommodation lag- dont accomm as much as 'demand' requires
blur stimulus can drive vergence via what type of crosslink?
accommodation-vergence
how can a blur stimulus drive vergence?
accommodation-vergence cross link
Blur drives a form of vergence called what?
accommodative vergence or blur vergence
What does the obicularis do?
active closure of the eye
what does it mean to eat the prism?
adapt to it - in phoria adaptation
Q What are the different ways to measure stability of fixation? -estimate the bivariate contour ellipse area during fixation -evaluate microsaccade freq and amplitude during fixation -evaluate drift amplitude and velocity during fixation -all of the above -none of the above
all of the above
Q fixation includes the following kinds of eye movements -drifts -small saccades less than 1 deg (microsaccades) -high frequency oscillations about 30-100hz (tremor) all the above none of above
all the above
what happens to the vision when the lens flattens ?
allowing for distance viewing and long range of focus
what happens to the vision when the depth of focus increases? and what happens to the tolerance of accomm error
allows for clear vision for more widely spaced objects and allows for MORE tolerance of accommodative error
does the normal or amblyopic eye have more domination of microsaccade rate?
amblyopic has less microsaccades than the normal rate
What does the ACA ratio describe?
amount of accomm convergence in prism diopters that happens when the eyes accommodate 1 diopter (-/+)
What is hofstetters rule?
amplitude = 18.5-age/3
what does approaching looming and going further looming cue?
approach means near further means farther
much of the activity involved in fixation involves movements on the scale of a few_____________?
arc min
what is the average size of a microsaccade and what is the size that it doesnt exceed ?
avg is 0.25 deg (15 arc min) dont get larger than 1 degree basically very small eye movements
what are the conditions that tonic vergence takes place?
awake
What is proximal vergence?
awareness of near
what happens at near VOR?
background shakes
BALANCED activity across both SC results in _______________. imbalance leads to _________________
balanced- fixation imbalance- microsaccade
the obicularis oculi also gets innervation from ___________ and other subcortical structures for control of spontaneous and reflex blinking , and emotional expressions of the face
basal ganglia
what do cortical defects cause?
bilateral ptosis
ocular misalignment can be viewed within a framework of what type of control of eye movements?
bincocular control
what is fine tuning pursuit of binocular position after a fast component and static alignment mostly connected with? what kind of circuit
binocular hering
in addition to eye misalignment, what else is disrupted in strabismic humans and monkeys?
binocular coordination of eye movements
What kind of vision does someone need for retinal disparity?
binocular vision
What is BCEA?
bivariate contour ellipse area
What is the disorder under excessive closure?
blepharospasm
what is due to an ocular dz which irritates cornea, such as dry eye uveitis or keratitis?
blepharospasm
what is the best driver of vergence when put together?
blur and disparity
what is the stimulus for vergence ?
blur and disparity
what is the pathway of blur?
blur goes to phasic accomm and then crosses and continues straight to tonic vergence and then to accomm
cells in the pretectal nucleus project to one or both EW nuclei via the posterior commissure?
both
on extreme downgaze, what happens to the activity of the superior rectus and levator activity?
both cease entirely almost
A patient has a unilateral lesion of the left fastigial nucleus what is the affect on the saccadic eye movements?
both eyes overshoot, left saccades and undershoot in rightward saccades
what muscles are activated when the eyelids are relaxed ?
both muscles have low activity and lids close due to reducing tone of the levator which normally keeps lids raised
what 2 adaptations take place in the disconjugate adaptation?
both saccadic and vergence components
what does looking at an eccentric target require generation of?
both vertical vergence and cyclovergence
electrical stimulation of a single site in the intermediate and deep layers of the SC with the eyes at different starting locations results in a what?
constant amplitude gaze shift
what happens at the end of the 4 neuron arc pathway?
constrict iris muscles
Q: in horners syndrome pupil constriction is what? and pupil dilation is what? normal or abnormal
constriction is normal dilation is abnormal
the obic oculi receives primarily ______projections from the motor cortex for voluntary control of blinks and eye closing
contralateral
what is the pupil control pathway parallel to?
control of accommodation
what is faster, convergence or divergence?
convergence
What is the near triad?
convergence is accompanied with accommodation and miosis
a disparity stimulus can drive accommodation by what kind of cross link?
convergence-accommodation
disparity stimulus can drive accommodation via what cross link?
convergence-accommodation cross link
What happens between vergence and accommodation control systems?
cross coupling
What does the vergence and accomm cross coupling models do?
cross the information in the blur-accomodaiton and disparity-vergence pathways
Amblyopes exhibit increased of decreased microsaccades? increased or decreased drifts ?
decreased microsaccades increased drift
what happens to the radius of curvature of the anterior and posterior surface of the lens during accommodation?
decreases
what is the measure of the angular movement of the eye?
degrees
What are the 3 different vergence measures?
degrees prism diopters meter-angles
movements of the left and right eyes made in response to a stimulus that changes in both _________ and ___________ is a simple sum or difference of separately generated vergence and conjugate movements
depth and conjugate position
How do you calculate the calculated ACA?
determine range of phoria at near and distance and then divide by the distance viewing
When do you get vergences? viewing objects at ______?
different distances
what is the regression movement usually associated with?
difficult passages and uncommon words
what system controls dilation and which controls constriction?
dilation-sympathetic constriction- parasympathetic
binocular anomalies at near can produce ___________ and interfere with reading , even in individuals with normal monocular vision
diplopia
What does monosynaptic mean?
directly send signals to the medial rectus
What type of adaptation happens with anisometropia?
disconjugate adaptation
what is the pathway of the disparity pathway?
disparity to phasic to crossing and straight to tonic and then vergence
if you were ranking vergence drivers in descending order of importance, which of the following would be an appropriate sequence?
disparity, blur, looming, size cues, awareness of near
fixation is _____________ whenever inappropriate eye movements occur on attempted steady gaze
disrupted
how are the 2 images focused and separated?
distance and vertically separated so that the 2 images dont interfere with each other
because the voluntary and involuntary pathways are _______, one can show deficiets which affect voluntary blinks but not reflex blinks and vice versa
distinct
BCEA measures dispersion of _____________ and _______________ eye positions during fixation
horizontal and vertical
What syndrome is a loss of sympathetic innervation to the eye, caused by damage at central levels (hypothalamus) ganglion levels or to the nerve itself?
horners syndrome
where do the preganglionic signals arise from?
hypothalamus via the cervical spinal cord
When we looked at the grid of all black squares at the black dot and then the white dot, what did we see?
image shift
where are vergence cells found in the superior colliculus?
in the rostral SC
it appears that the context of viewing a near target causes an increase or decrease in VOR gain?
increase
what does pupillary constriction helps to increase to reduce amount of accommodation needed?
increase depth of field
what may be the cause of presbyopia?
increase stiffness of the lens with age
What happens to depth of focus as the pupil gets smaller?
increases
standard deviation of fixational eye position are largely independent or dependent of stimulus parameters?
independent
what is the sympathetic innervation providing ?
inhibition needed for a push pull system
what does divergence speed depend on?
initial vergence position
what is the reading eye movement that is a small saccade which takes the eye from one fixation to the next?
inter fixation saccades
Converting MA to degrees depends on what value?
inter-pupillary distance
Which of the following disease conditions could be used as supporting evidence for herings framework for binocular control?
internuclear ophthalmoplegia
what kind of eye movement is showing when someone cant do conjugate eye movements to one side but is able to do vergence abduction?
internuclear opthalmoplegia
reflex blinks can occur involuntarily or voluntarily and concious or unconcious?
involuntary unconciously
What controls the obicularis oculi?
ipsilateral facial nucleus in the brainstem
what is the question of interest when it comes to eye movement responses?
is it the sum of individual responses or are there more complex interactions in the brain?
why is it important to formalize the link between vergence and accomm?
it helps understand the neural control and helps understand disorders
what does having a catch up saccade during a SP do to help?
it improves the accuracy of the eye movement making it optimal and not guessing where the object is at
why is fusional vergence better?
it is faster -is the sum of the direct combination of accomm and convergence -also improves with binocular viewing because of the crosslink
what does binocular and monocular horizontal line take out of the situation?
it takes out the disparity- the horizontal stick will look the same no matter if it is coming toward or going away from you if cant see ends of the stick
what happens to the pupil size when it is having light adaptation?
it will change from a 2mm-8mm and makes a 16 fold change in the light entering the eye
what is the cause of essential blepharospasm?
its idiopathic
why is the response larger than the sitmulus aca?
lag of accommodation
do voluntary blinks have large or small amplitude and last shorter or longer than reflex blinks?
large amp longer lasting
What happens with the size of fixational movements when there is a larger object? small object?
larger fixation movement smaller fixation movement
The muscle planes for the right inferior and superior recti are roughly parallel to?
left posterior semicircular canal
What happens with the lens vertically during accommodation?
lens drops slightly under influence of gravity
what changes in the anatomy during accommodation?
lens shape (thicken)
what part of that beetles eyes is the bifocal?
lens- middle and periphery regions have diff powers
are these cues less or more effective drivers?
less effective
why is there fading in the amblyopic eye?
less microsaccades to make it a fresh stimulus in the problem eye
in primary gaze, what muscle must maintain constant tone to keep the upper lid elevated?
levator
what is the muscle that elevates the upper lid and what innervates it?
levator 3rd nerve
Q The ____ muscle is responsible for keeping the eyelid elevated and the _______ muscle is responsible for active closure during a blink
levator obicularis oculi
What happens with the levator and Obic oculi during a blink?
levator inhibited obicularis activated
What are the muscles involved in blinks?
levator palpebrae mullers muscle frontalis muscle
what muscle remains activated througout a WINK and what one can turn on an off?
levator remains active can control one obicularis oculi and increase force above the levator
What is it when eyelids fail to lower as gaze is lowered?
lid lag
VOR gain is better in the __________ (with OKN) than in ________________ (without OKN)
light dark
what accounts for most of the interaction? is that true for all interactions?
linear superposition NO there are nonlinear effects as well
Precision of fixation varies a lot or a little with stimulus parameters?
little
what is a square wave jerk?
look away from the target and then back to the target
what happens when there is high frequency of motion?
lots of retinal slip
Infants have a high or low blink rate?
low
what does pseudo ptosis mean?
low hanging lids
what is a common ocular disease that causes a central scotoma and eccentric fixation?
macular degeneration
what does a peak lid velocity result in?
main sequence for lid closure
Why do we blink?
maintenance of tear film removal of foreign bodies protection from looming objects
How does the brain generate eye movements in depth (3-D)?
making movements in depth- two eyes are moving diff amounts
what horners syndrome the first sign for?
malignant tumor
Where are the disparity sensitive cells found?
many cortical areas! v1,v2, v3, v3a, MT, MST, LIP
What is measures the effort for vergence?
meter angle
a 1 yr old child and a 25 yo adult are viewing an object 25cm in front of their eyes. which of the following methods express their vergence angle would be the same in the 2 subjects ? degrees prism diopters meter angle a,b abc
meter angle independent of PD
What is the amount of convergence required to view an object at 1m?
meter-angle
What eye movement is the only 'good' idea of a mechanism that is underlying fixaitonal eye movements?
microsaccades
what part of the brain is the SOA in?
midbrain near response cells
there is evidence that the saccadic system is able to use ____________ to encode the ____________ of the catch up saccade
retinal slip velocity amplitude
what is the reading eye movement that is a large saccade which take the eye to the beginning of the next line of text?
return sweeps
where are the neurons located in the brain that encode microsaccades?
rostral collilculus
what type of interaction are catch up saccades having?
saccade-SP
during scanning eye movements, a series of ___________ are made in order to inspect a scene
saccades
eyes scan a line of text with a series of ___________ during reading
saccades
stimulation of the rostral fixation zone of the SC seems to suppress vergence in addition to what?
saccades
what kind of eye movements do blinks facilitate?
saccades
what are microsaccades used for?
scanning
What kind of transformation is required to generate vergence motor commands from sensory disparity signals?
sensorimotor
how does a cat, racoon, lamprey change focus?
shifiting in lens position
the peak velocity of fast vergence eye movements is ______________ the peak velocity of the similar amplitude saccadic eye movements
significantly slower than saccade is 800 and vergence is 100
neural recordings in the PPRF during asymmetric vergence suggests that these cells encode movements of what instead of conjugate signal?
single eye
what are the cues that help drive vergence eye movements?
size texture looming (motion)
___________ and ___________ matters- higher stand dev for disk targets and larger targets
size and shape
does phoria adaptation have a slow or fast adaptive process?
slow
Normal regressions tend to be larger or smaller than the inter-fixation saccades that preceed them?
smaller
What rate and amp does the high freq tremor of the eyes have?
smallest amp rate of 30-100 hz
One hypothesis was that fixation was simply _______________-_________ (gaze holding eye movement) at zero velocity
smooth pursuit
The saccadic system can respond to positional retinal error during ______________________.
smooth pursuit
what is slow vergence neccessary for? kind of eye movement
smooth pursuit
when slow drift creates errors, are they only bad errors or some are good too?
some toward object and some away from object
saccades speed or slow the ongoing vergence movement suggesting that that the brain does or does not simply process conjugate and vergence errors separately
speed up does not
release of tension of the zonular fibers causes the lens to become more?
spherical
What kind of blinks are made without any specific stimulus or effort?
spontaneous blinks
what does the eye movement trace during reading represent?
staircase
what is the aca that compares the convergence to the accommodative stimulus (diff from the response) ?
stimulus aca
what condition makes herings hypoth fall apart?
strabismus- losing BV and 2 eyes are NOT tied together as one
When an object is brought closer to the subject, it appears blurry because why?
subject is focused behind the object
where does the sympathetic nerve fibers ascend from?
superior cervical ganglion at the base of the skull
what is the better and main way to cancel out VOR? which of the 2
superposition of the VOR and SP signals
what part of the cortex is important for predicative vergence eye movements ?
supplemental eye fields
OKN ______________ VOR at _________ frequencies
supplements low
What part of the brain is responsible for the vergence signals?
supraoculomotor area (SOA)
What is the alternative theory called? is there much evidence for the theory?
tension theory no
what does this prove if only vergence is possible?
that there is a separate pathway for vergence and conjugate eye movements
what does the pupillary light reflex control?
the diameter of the pupil in response to light intensity
how do the ellipses of horizontal vs vertical eye movements change as it goes from normal to strab viewing eye to strab deviated eye?
the ellipses get bigger from normal to strab viewing to strab deviated
what does this light adaptaion allow for?
the eye to adjust for changes in light level
is the gain higher or lower with SP movements in an eccentric location verses being straight ahead?
the gain is lower in the eccentric position
why does the head take longer to turn in the head-eye saccades?
the head is heavier and has more INERTIA
if retinal disparity is non-zero, what does it mean?
the image is falling on a Non Corresponding retinal areas
what happens when the ciliary muscle causes the zonular fibers to become taut?
the lens flattens
what is vision controlled by?
the lens which is controlled by the suspensory ligaments and ciliary muscle
where is the CCN near by?
the oculomotor nucleus (that controls SR)
what happens when the choroid is pulled forward ?
the retina is stretched slightly
what do the 'steps' represent?
the saccades
what happens with the zonular fibers during accommodation?
the tension is released
what does the longer latency mean for accommodation in older people?
the time to accommodate will take longer
Does congenital nystagmus increase or decrease with attention or fixation?
Decease
T/F in peripheral vestib nystagmus the other eye movements are not reserved
False they are
What is the jerk nystagmus described by? Which direction, of the slow or fast phase?
Fast
What makes up a jerk nystagmus ?
Fast phase and slow phase
What does a right beating nystagmus have?
Fast rightward phase and slow leftward phase
What is the resetting phase? Fast or slow?
Fast that's why we care more about the slow phase
What can the peripheral vestibular nystagmus be suppressed by?
Fixation So to tell is by testing PVN by removing fixation
What is the purpose of the head turn or head shake?
For the null to be straight ahead
_________ periods are periods during the waveform when the eyes are still, vision is acquired during these periods
Foveation periods Keeps the image stable
What kind of nystagmus shows an exponentially decreasing slow phase?
Gaze evoked nystagmus
What comes with INS/CN?
Head shaking or head turn
What are the 3 components for acquired pendular nystagmus?
Horizontal vertical and torsional
Where does the problem tend to show up in the cerebellum when they have periodic alternating nystagmus?
In the nodulus or uvula
Nystagmus increases or decreases intensity with gaze eccentricity?
Increases
What is another name for congentialy nystagmus?
Infantile nystagmus syndrome
Where does the fastigial nucleus and posterior interposed nucleus project to?
SOA
what responses are added to get an eye movement for cancellation?
SP response+VOR response
What kind of nystagmus does someone have if they have vertical disjunctive component and conjugate torsional component?
Seesaw or hemi-seesaw nystagmus
What if the pathological vestib nystagmus is peripherial in origin? That means there is a dysfunction in what?
Semicircular canals Otoliths Or vestibular nerve
What does pathological nystagmus lead to?
Slip of images on the retina
________ phases may be linear, increasing or decreasing velocity
Slow
________ ___________ is a disorder affecting infants and young children. It involves rapid, uncontrolled eye movements, head bobbing, and sometimes, holding the neck in an abnormal position
Spasmus nutans
What are the pathological nystagmus associated with specific what 2 things?
Specific eye disease Specific eye movement systems
what encodes the desired gaze displacement?
Superior colliculus
T/F cells that are in the SOA that encode vergence also encode accommodation
TRUE
T/F in addition to disparity and blur, other cues may help drive vergence eye movements
TRUE
T/F in the real world, eye movement stimuli are varied and do not stimuluate only one type of eye movement system
TRUE
T/F rapd can appear as paradoxical dilation of pupils when light is presented to bad eye after normal constriction due to presentation of light to the good eye
TRUE
T/F there are changes in both vergence and conjugate positions in movements of depth
TRUE
T/F vergence is highly adaptable
TRUE
T/F we blink to help visual motor coordination?
TRUE
where does the NRTP project to?
vermis and directly to the FN/PIN
what is an example of a near anomaly in a normal monocular vision pt?
vertical phoria - they can lose their place at the beginning of a line of text
what is used to compensate for vertical phorias?
vertical vergence and cyclovergence
what two things must interact to get the gaze on the target?
vestibular response and the head response
amblyopia, RE, presbyopia are examples of causes of reading difficulty because they have a loss of?
visual clarity
why dont people notice spontaneous eye blinks? what 2 principles
visual masking effects and visual suppression effects
What blinks are made on command?
voluntary blinks
square ________ ___________ occur occasionally in normals
wave jerks
what times will the cancellation not work?
when the head is still and the target is moving at high frequencies
why is the calculated greater than the gradient aca?
will take into account proximal vergence
symp nerves pass through the ciliary ganglion with or without synapsing?
without
can inter-fixation movements jump over the first part of a word or several words?
yes
is the degree range adaptable/ plastic with shrinking and expanding the ranges with only eye movements or head only?
yes
Are microsaccades intentional movements?
yes - they are not random
is vergence still possible when the MLF (Hori eye movements) is lesioned?
yes because it doesnt control vergence
are large saccades encoded here?
yes just more caudal
can this happen the other way where pupil constriction can happen without accomm controlled by the EW nuc?
yes!
young pts with central scotomas tend to develop more stable ________, while older patients tend to be more __________
young-stable PRL older -variable PRL
what is the tension on the lens caused by?
zonular fibers
what is the velocity of fixation?
<4deg/sec
smooth pursuit has a limited range of ___________deg/sec and a ______ latency to sudden changes in target velocity
<90 130 msec
What is pathological nystagmus?
A disorder of eye movement control associated with a variety of conditions
what determines the strength of this crosslink of the blur stimulus?
ACA ratio
what is the strength of the accommodation-vergence crosslink defined by?
ACA ratio
if the near phoria=far phoria, then what other things are equal?
ACA=PD
Pathological nystagmus can be either congenital or ——-
Acquired
During eye-head saccades... -eyes move forward -VOR is negated for movement prior to attaining gaze goal -head stops after gaze Goal is reached -VOR kicks in once gaze goal is reached -all of the above
All of the above
Where are the lesions around when someone has jerk or hemi-seesaw nystagmus?
Around the interstitial nucleus of CAJAL (vertical)
Where are the lesions when someone has pendular see saw nystag?
Around the optic chiasm and will cause pendular seesaw
Someone with vestibular and gaze evoked nystagmus develop what in order to see clearly?
Develop head turn so the null eye can see clear
Often pathological nystagmus are of ——- value
Diagnostic
Convergence and head posture has or doesnt have an effect on ventral vestibular nystagmus?
Does have
What direction is the fast phase in downbeat nystagmus?
Downward is the fast phase e
what do the cues do then?
fine tune binocular eye position following vergence eye movement
What muscle is the antagonist of the levator?
obicularis oculi
what happens with obicularis and levator at the end of a blink?
obicularis shuts down levator resumes former tone both cant contract
High resolution recording of oculomotor activity reveals that the eye moves also during these periods. The line of sight continually wanders with a seemingly random trajectory called _________________ occasionally interrupted by saccades with small amplitudes called ___________________________.
ocular drift microsaccades
why does does someone only use eye movements in the 35-40 range?
ocular motor performance deteriorates when the eye is eccentric in the orbit
the responses to these stimuli are also complex involving more than one __________________ __________________
oculomotor sub-system
What is the peak velocity of a blink?
on the order of saccadic peak velocity -800deg/sec
the beetle has 2 retinas, how are they arranged?
one behind the other so that the sharp image from each lens region falls onto a diff retina
what does the obicularis oculi muscle surround? what action does it have?
palpebral fissure sphincter action
what system innervates the ciliary muscle?
parasympathetic
What are some other disorders in fixational control
pathological intrusions nystagmus
what is the aca ratio that compares the convergence to the actual accommodative response ?
response ACA
what is tonic vergence?
resting state of vergence
What are the 2 stimuli to vergence?
retinal disparity and blur
what is the stimulus for OKN?
retinal slip due to LARGE field stimulus
what is the stimulus for smooth pursuit?
retinal slip velocity
how many mm is the SOA dorsoalateral to the oculomotor nucleus?
1-2mm
What is the hz that is for acquired pendular nystagmus ?
1-8 pendular waveform
why does the black dot stay visible?
1. receptive field is very small- shifting gaze slightly will see on new recep field 2. fixational eye movments are switching fields
what is the 4 neuron arc steps of pathway for the pupillary light reflex?
1. retinal ganglion cells 2. via optic nerve, the pretectal nucleus 3. EW nucleus 4. via oculomotor nerve- the ciliary ganglion
what are the 2 ways to cancel out VOR ?
1. superposition SP and VOR signals 2. reduction in head movement sensitivity -from canals in ear
what percent of all inter fixation movements is regressions?
10%
how large in arc min are slow drift movements?
10-15 arc sec
what is the amplitude of levator excursion from downgaze to upgaze ?
12-17 mm
what is the typical spontaneous blink rate per min?
15-30
how many log units does the light on the retina change by?
2 log units for a 250 msec pattern
what is the infant blinks per min?
2 per min
Where are the quick phases directed in peripheral vestibular nystagmus? Away or towards the lesion?
Away from the side of the lesion So slow towards the lesion
How long is the duration of a typical blink?
200-400 msec covers pupil in half that time
What is the latency of vergence eye movemets?
200msec
What is the latency for the lid when having irritation or sudden loud sounds?
25msec
how many classifications are there for horners syndrome?
3
what is the equivalent degrees for a 6cm interpupillary distance?
3.4 degrees
under normal conditions of visual scanning, humans tend to use their eyes only within a range of ________________ degrees
35-40 degrees
what type of movements are made from saccade vergence interactions?
3D movements
how many different disorders of lid control are there?
4
how many neurons are there in the 'arc' for pupillary light reflex?
4
What is the typical amount of arc min for drifts/sec?
45 arc min
what is the length in arc min between ocular drifting during fixation - making microsaccades between
5- 10 arc min
how many pairs of eyes does a diving beetle larva have?
6 pairs 1 primary and the rest bifocal abilities
What percent of your waking day is with your eyes closed if each blink is 1/4 sec?
6-12%
what percent ellipse is formed from the BCEA?
68% confidence ellipse
what percent of reading time is spent in fixation periods?
90%
what percent of the inter fixation saccades are left to right movements?
90%
How large are microsaccades in deg?
<1deg
Q: which of the following statements about interactions between eye movement systems are true? -there is no interaction between eye movement systems -most interaction can be explained by linear suppression -there is evidence for nonlinear interaction between system -all of abc -b and c
B and c
Which of the following experimental observation provided evidence for non linear interaction between saccade and vergence systems - peak velocity of the vergence component saccade vergence movement is equal to peak velocity of a similar amplitude vergence only movement -peak velocity of the vergence of combined component saccade vergence movements is less than peak velocity of a similar amplitude vergence only movement -peak velocity of the vergence component of a combined saccade vergence movement is greater than peak velocity of a similar amplitude vergence only movement -lesion of the MLF affects saccadic movements but not vergence -vergence related neural responses can be found at several areas in the brain adjacent to saccade related neural responses
C similar amplitudes
the strength of the crosslink of the disparity stimulus is defined by what?
CA/C ratio
what is the strength of the convergence-accommodation cross link defined by?
CAC ratio
what does the fastigial nucleus have neurons related to?
CONvergence
for the cac ratio, what must equal to get perfect yoking?
Ca/c = 1/pd
Is congenital nystagmus developed during infancy or born with?
Can be either-why they changed name to infantile nystag syndrome
What kind of nystagmus shows a exponentially increasing slow phase?
Congenital nystagmus
Is pathological nystagmus conjugate or disconjugate?
Could be both
Will pathological be peripheral or central in origin?
Could be either
what does the post interposed nucleus have neurons related to?
DIvergence
For gaze evoked nystagmus, it should be differentiated from end point nystagmus and one way to tell is what?
Exponentially decreasing slow phase that is directly towards the center (fast away from the center)
T/F blinking does not help people with oculomotor apraxia (paralysis of voluntary gaze control) initiate saccades
FALSE
T/F return sweeps start at the LAST character at the end of the line and the FIRST character at the beginning of the next line
FALSE start a few charaters from the end and then a few past the first in the next line
T/F aca and cac are ratios that are dependent on each other
FALSE they are independent of one another
T/F the head stops after the gaze goal is reached
FALSE it keeps going
T/F you can voluntarily flex one levator muscle and cant contract just one obicularis oculi
FALSE opposite
T/F microsaccades are driven through a different circuit than normal saccades
FALSE same circuitry
T/F blink rates remain pretty constant across individuals and tasks
FALSE they vary
vergence neurons are adjacent to the saccade neurons in the?
FEF
where in the cortex is vergence eye movements signaled?
FEF- frontal eye fields SEF -supp eye fields
Is the nystagmus different in the two eyes?
It can be
Why do we label it by the fast phase if the slow phase is what is more important?
It is easier to see by the clinician
What does a mixed nystagmus waveform look like?
It is mixture of sine wave and jagged peaks
What does a jerk waveform look like ?
Jagged mountains
What are the 3 types of waveforms that are distinguishing features of nystagmus?
Jerk Pendular Mixed
Vergence position = ___ position - _____ position
LE position - RE position
what is the equation for vergence?
LE postion-RE position
What is another name for fusional maldevelopment nystagmus syndrome?
Latent nystagmus
On what gaze is nystagmus observed on?
Lateral gaze
What does a gaze evoked nystagmus indicate about the brain processes?
Leaky neural integrator function - inability to maintain eccentric gaze
What is a telling sign in peripheral vestibular nystagmus?
Linear slow phase
What is acquired pendular nystag associated with? What diseases?
MS And oculopalatal myoclonus
Is INS/congenital nystag mainly horizontal or vertical with smaller horizontal or vertical/torsional components?
Mainly horizontal with smaller vertical and torsional components
What does the waveform look like for congenital nystagmus?
Mixed pendular and jerk
Does the head and eye start at the same time in eye head saccades?
NO
are the tremors correlated in the 2 eyes?
NO
Is central vestib nystagmus well suppressed by fixation?
NO That's peripheral
there is a constant amplitude gaze shift, but are all the combinations of eye and head amplitudes the same as well?
NO they are different
What is a common muscle palsy that have reading diffculties because they cannot __________ adequately
SO can depress adequately
OKAN tends to cancel out what?
PRN dancer doing turns
A general term for nystagmus caused by imbalance in push pull vestibular system is what?
Pathological nystagmus
- —- ———— is Normally occurring eye movement designed to keep the eyes within a normal working range
Physiological nystagmus
What does the R and L colliculus control?
R controls L movement L controls R movment
What is the equation for conjugate RE and LE movements?
RE+LE/2 the average of the 2
Is a purely horizontal nystagmus rare or common?
Rare for central vestib nystag
What is nystagmus?
Repetitive to and fro movement of the eyes is defined as nystagmus
What does a pendular waveform look like?
Rolling hills or sine wave
Alexanders law states that interaction between vestibular nystagmus and gaze evoked nystagmus is what?
The nystagmus is null on one side because they cancel out and increase in nystagmus more eccentrically to the other side because they add together
where does the fastigial nucleus and posterior interposed nucleus recieve projections from?
vermis
What is the goal of physiological nystagmus is what?
To keep the image slip small
What type of suppression follows a saccade in acquired pendular nystagmus ?
Transient - nystag will dampen then come back
what ratio do you use when vergence stimulates accommodation?
ca/c ratio
What is the ACA ratio that is determined from the phoria measure at far and near using an equation?
calculated
which is normally a higher value, calculated aca or gradient aca?
caluculated
are the drifts conjugate or disconjugate
can be both -combo of vergence and versions
during CEHT (combined eye head tracking) or HFT (head fixed tracking) the VOR signal is counterproductive and must be __________?
cancelled out
what are the incidences of the central preganglionic postganglionic in percents?
cent- 13% pre-44% post-43%
What nucleus controls the levator?
central caudal nucleus via the oculomotor nerve
what is the hemholtz framework when it comes to depth movements?
central parts of the brain are developing commands for each eye independently like a chameleon
What is the hering framework when talking about brain generations of seeing depth movements?
central parts of the brain are developing commands for the conjugate and vergence SEPARATELY
Eccentric fixation happens when patients have a what?
central scotoma
what are the 3 classifications for horners syndrome? think in regards to a nerve
central, preganglionic, postganglionic
how does an eel change focus?
change its axial length
how does an owl change its focus?
change its corneal shape
humans and non human primates change focus how?
change lens shape
what does the sympathetic innervation pass directly?
ciliary ganglion
what ganglion and nucleus are important in the accommodation control?
ciliary ganglion and ed westphal nucleus
Q: what happens with the ciliary muscles and the zonular fibers during the relaxation theory?
ciliary muscles contract and zonular fibers become less taught
Where do the vergence cells lie close to in the nucleus reticularis tegmenti pontis (NRTP)?
close to the smooth pursit and saccade cells
what does larger in size cue?
closer
the amount and duration of dimming are reduced in our perception so the gap is doing what?
closing in
even though the levator neurons project to only one eyelid, they are ______________ in the CCN and therefore achieve bilateral control of eyelids
co-localized
what is excessive retraction of the lids on attempted upgaze?
colliers sign
what are the 2 disorders that are under excessive opening?
colliers sign lid lag
What is BCEA used to measure?
common method to measure fixation stability
there is a lot of evidence that interaction between eye movement systems is ____________
complex
under herings framework for binocular control, the brain processes _______ and __________ eye movements separately
conjugate , vergence
what can any 3d movement be broken into?
conjugate and vergence parts simultaneously
vergence is an independent eye movement subsystem and is controlled separately from what kind of eye movements?
conjugate eye movements such as saccades
which muscle is conjugate and which one can be controlled monocularly?
conjugate is levator monocularly is obicularis oculi
slow oscillatory movements are __________ vertically and ___________ horizontally (conjugate or disconjugate for both)
conjugate vertical disconjugat horizontal
what is the calculation for just the LE movement?
conjugate+vergence/2
What is the calculation just for RE movement?
conjugate-vergence/2
The 2 eyes move mostly -_________ during a blink
conjugately
What type of response is it when both pupils constrict even when stim is only in one eye?
consensual response
What are the 4 compnents of visual function?
drifts microsaccades tremor slow osicllations
why does the gain need to be greater than 1 when eyes fixate on a near target with VOR?
due to geometry considerations adn the fact that the eyes are NOT the center of rotation
what is a condition in which there is reading difficulty without a obvious visual or oculomotor defect?
dyslexia
strabismics will also sometimes show _____________ ___________, even though the fovea may be intact
eccentric fixation anomalous retinal correspondence
what is the ganglion and nucleus what the innvervates the ciliary muscle?
edinger-westphal nucleus ciliary ganglion
in clinic, is examining each system in isolation effective or ineffective?
effective!
Q Identify the true statement of the superior colliculus and fixation -its located caudally -encodes microsaccades -encodes drifts -encodes tremor all of above
encodes microsaccades it is rostral no evidence for drifts and tremor
oculomotor apraxia is sometimes accommpanied by ___________________, but specifically in relation to initiating saccades
excressive blinking
where is there an issue/ what is the syndrome with lid lag?
extrapyramidal syndromes
movements beyond the 35-40 deg range are usually achieved with a combo of what?
eye movement and head movement
what responses are added to get gaze?
eye+ head
what is another term for gaze?
eye-head saccades
what happens when someone is under anesthesia and sleep?
eyes drift outward (not in tonic state)
what things are affected with insufficient closure?
facial nerve nucleus basal ganglia-parkinsons frontal lobe lesions
there have been reports of rapid ___________ of targets during monocular fixation with amblyopic eye
fading
T/F tremor is large enough to make a visual effect
false small doesnt cause visual effect
does near or far VOR have greater gain ?
far
what does an uncrossed disparity give rise to the perception of? and what is this the stimulus for?
far stim to diverge
what is the amalgamated (combined) framework for binocular control?
fast and slow vergence systems
Which of the following experiments yielded convincing evidence that the SOA encodes a vergence signal? a. experimental lesion near OMN produced a deficit in vergence but not conjugate eye movements b. firing rates of neurons in the SOA showed modulation of activity during a vergence eye movement but did not show any modulation during conjugate eye movements c. anatomical studies showing that the SOA is connected to the fastigial nucleus d. in INO patients show a deficit in conjugate control but not vergence
firing rates of neurons in the SOA showed modulation of activity during a vergence eye movement but did not show any modulation during conjugate eye movements ** a is too difficult to do c and d are true statements but doesnt answer questiosn
Eyes move constantly despite attempt to?
fixate on a stationary object
when does our visual experience happen? what kind of eye movements?
fixation eye movements
what was demonstrated when going from the black dot to the white dot?
fixational eye movements (from the shift)
what is the normal reading eye movement that has periods of eyes being relatively still ?
fixations
What is Troxler Fading?
focus on black dot in center and the ring around dissapears
what were we doing when fixating on the black dot?
forming an after image
which part is affected if someone cant wink?
frontal lobe lesion think taking away personality
Does a partial or full blink have a higher peak velocity?
full
what is better, fusional vergence or accomm convergence?
fusional vergence
what is the form of vergence does retinal disparity drive ?
fusional vergence or disparity vergence
what does the 'straight' part of the staircase represent?
going to a new line while reading
what is the aca ratio that is measured by inducing accommodation with lenses and measuring the change in convergence?
gradient aca
do blinks increase or decrease with adult levels?
gradually increase from infancy
when the eyes are fixated on a near target, the VOR gain must be greater or less than 1 during head rotation?
greater
how large are the movements of tremor in arc min?
half arc min
what is special about an anableps? (south american trout)
has bifocals with 2 pupils that allows it to have clear vision above and below water
What is the stimulus for VOR?
head movements
which happens first in the head eye saccade, the head or eye ?
head starts later and the eyes move first
Who proposed the relaxation theory of accommodation?
helmholtz
What framework does pre-motor drive support and why?
helmholtz because it is monocular
What framework is more useful clinically?
hering
Internuclear ophthalmoplegia is a support for whos hypothesis?
herings
what is lid retraction in the opp eye to the ptosis an example of?
herings law
what does high spacial freq and low spacial freq cue?
high spacial is close low spacial is far
what can a unilateral defect in the optic nerve in front of the optic chiasm or severe retinal disease cause?
relative afferent pupillar defect RAPD
position errors (within fovea) must be kept to a _____________ to optimize VA for stationary objects
minimum
What kind of viewing conditions is 'blur driven accommodation' studied in?
monocular
what kind of circuits does the fast vergence use mostly?
monocular circuits supports helmholtz
what stim uses monocular and which uses binocular?
monocular- blur vergence binocular is disparity vergence
what kind of connections to the medial recuts motorneurons are made from the SOA?
monosynaptic
What does a larger ellipse indicate?
more instability in the eye fixation (so it increases with disease conditions)_
what happens when you find a deficit in one system?
most likely another system is making up for it (ex using saccades if something is wrong with SP)
Restriction of _______________ can be a cause of reading difficulty
motility
Herings framework: separate conjugate and vergence components of eye movements are summed at the level of what?
motorneurons
What 2 muscles play a more minor role?
mullers and frontalis
what does a crossed disparity give rise to the perception of? and is the stim for?
near stim to converge
when the lens is becoming more spherical, what is that allowing for vision?
near focus
Is the blur and disparity pathways under negative or postive feedback?
negative
divergence is positive or negative?
negative
only ring like ciliary muscle is under what kind of control?
neural control
close association between vergence and accommodation are controlled at which level?
neural level
where is the problem at if someone has a unilateral ptosis?
neuromuscular junction or CN 3
do fixations correspond to individual words in the text?
no
if someone has an RAPD then do they have a response when a light is shown to affected eye?
no
is there an antagonist muscle that goes against the ciliiary muscle?
no
are spontaneous blinks responses to dry eye? why or why not
no because anesthicized eyes still maintain blinks at normal rates
do the graphs look messed up with people that have congenital nystagmus ?
no because they have adapted to the problem
does vergence and saccades get controlled by the SOA?
no only vergence
Does vergence angle or visual information modulate VOR gain?
no there is no evidence of that
is the SD of fixational eye positions due to contrast and luminance?
no they are independent
Which of the following is the result of neural adaptation within the vestibular system? VOR gain with CL sustained head movement Myopes with SL reversal of nystagmus
none of the above
what is the marginal reflex distance MRD
normally 3-4 mm
What is the meausurement of width of the palpebral fissure?
normally 9-11mm
Accuired or congenital _____________ may disrupt reading by reducing the effectiveness of fixations- although many pts adapt to this problem
nystagmus
Q Pick the true statement -peak velocity of eye blinks are significantly lower than that of similar amplitude saccades -peak velocity of eye blinks show a main-sequence relationship to blink amplitude that has the same form as a saccade main sequence -peak velocity of eye blinks is lineraly related to blink amplitude -two eyes are disconjugate during a blink -none of the above
peak velocity of eye blinks is linearly related to blink amplitude
what type of adaptation is of the tonic vergence component?
phoria adaptation
vergence adaptation is made up of what 2 types of adaptation?
phoria and disconjugate adaptation
what is an example of a time when more than one eye movement is being stimulated?
playing tennis running on the treadmill and watching a show
what is the stimulus for saccades?
positional retinal error
Convergence is positive or negative?
positive
which (anterior or posterior) curvature decreases less?
posterior surface
Typically pts with central scotoma will pick a particular spot outside the fovea to fixate with and this is called ______________________________
preffered retinal locus (PRL )
What do fixation movements do?
prevent fading
eyes tend to rotate to ______position during a blink
primary viewing position
what is the measure of deviation of 1cm at a distance of 1m? what is the equivalence in degrees?
prism diopters equiv to 0.57 deg
what is the problem with colliers sign?
problem with vertical gaze centers rimlf or cajal
are the saccade system and control of vergence reponses processed separate or together?
processed together
what is another name for proximal vergence?
psychic vergence or voluntary convergence
what are the 2 under insufficient opening of the lids?
ptosis and pseudotosis
what happens to the choroid during accommodation?
pulled forward
what happens when the ciliary muscle contracts?
pulls toward the axis of the eye
What is the most prominent symptom of horners syndrome?
pupil constricting normally under bright light or near viewing, but wont dilate slowly to dim light or emotional stimulus
An observer looks at a static scene and ___________ separate the periods of fixation in which visual information is accquired
rapid eye movements (saccades)
what does this regression depend on?
reading difficulty
in a patient with a stable PRL, saccades become ______________________, so that the saccades made to a peripheral target will cause the target to land directly on the PRL
recalibrated
why does this troxler thing happen?
receptive field away from the fovea is larger - must shift focus always to see ring and dot
What happens to the lens diameter during accommodation?
reduced slightly
what 2 types of abberations are reduced when the pupil constricts in order to produce sharper retinal images?
reduced spherical and chromatic abberations
What happens to light on the retina when someone blinks?
reduces light level
What reduces and increases during presbyopia?
reduces range reduces gain increase in latency
What kind of blinks are made in response to a specific stimulus such as a flash of light, sudden loud noise, corneal irritation, looming objects
reflex blinks
where is the supranuclear control of the levator found?
regions in the cortex show lid elevation when stimulated
what is the reading eye movement that has small saccades which go in reverse direction (right to left)
regression
what does reading in a patient with amblyopia have more of? what increases in duration?
regressions and increased fixation duration
what is normally a larger value, the response or stimulus aca?
response
What does it mean to have a disorder of fixation control ?
there is too much control
why are all diff eye movements unique?
they have different specific stimuli
what do the stair graphs look like in patients with visual spatial dyslexia compared to the normal reader?
they have large regressions inaccurate return sweep saccades reverse staircase patterns
what does prism cause in adaptation of the R and L eye?
they move different amounts with prism on
is this the same mechanism of suppression like saccades?
thinking yes but dont know that for sure
how does the retinal slip with high frequencies matter when talking about cancellation of movements?
this is why the reduction of head motion sensitivity comes into play
what is the point of the fixational eye movements?
to gain more information about the target
prolonged viewing of a near stimulus changes what kind of vergence? 'default'
tonic
is smooth pursuit movements in the periphery tough or easy?
tough- person will move head instead
T/F accomm-vergence has different dynamics than fusional-vergence
true
T/F blinks can help break fixation
true
T/F it is an adapted state of looking at near target
true
T/F studies of saccade-vergence interaction have led to proposal of new monocular framework for control of eye movements
true
T/F the 2 eyes must rotate through different amounts
true
T/F there is a summation going on in the medial rectus motor neurons
true
where is disparity encoding happening in the cortex?
v1 MT/MST- temporal LIP -lateral inferior parietal
_____________ ___________ is a property of both systems
velocity storage
what is slower, vergence or saccades?
vergence
What kind of eye movements does the SOA respond to?
vergence ONLY not saccades (slide with the firing and showing both kinds of movements)
what are the cerebellar flocculus neurons in charge of?
vergence but mainly changing VOR gain with vergence angle
what happens along with the accommodation and vergence systems?
vergence eye movements
what could ocular misalignment be directly a problem of ?
vergence mechanisms
What is the vergence object stimulus and defocus stimulus?
vergence object stim is disparity defocus stim is for blur vergence
