Binocular Vision Test 2

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What is also known as Dark Focus?

tonic accommodation

What is the cause of night myopia under total or relative darkness?

tonic accommodation

What is the expected amount of tonic accommodation?

1/2 to 1.5 diopters

What is the cause of tonic accommodation?

the balance between the parasympatheric and sympathetic nervous system

What type of accommodation is used to obtain clear focus and is linked to changes in stimulus distance?

reflex accommodation

What is also known as Psychic accommodation or instrument myopia?

Proximal accommodation

What is a normal AC/a ratio?

4/1-6/1

What is a normal CA/c ratio?

0.06 D/ change in PD

What is the average latency of accommodation?

380 ms

What is the response time for accommodation?

about 1 sec

What are three stimuli for accommodation?

Blur
Chromatic aberration
Binocular Disparity

In the accommodative stimulus -response curve, at what point is the hard saturation met?

amplitude of accommodation

What are the components of an accommodative lead?

tonic accommodation plus depth of focus

What are three factors that can affect the accommodative response?

Luminance
Contrast
Retinal Eccentricity

True or False
The accommodative response is greatest when the stimulation is peripheral.

False

What factors determine the accommodative response?

depth of focus/pupil size
stimulus properties
tonic accommodation
physical properties of the lens

Describe the neural pathway until the FEF?

Optic nerve-Optic tract-LGN-Optic radiations-Visual Cortex-Frontal eye Fields

Describe the efferent pathway of accommodation?

FEF-EW nucleus-CN III- ciliary ganglion- short ciliary nerve

What neural input is thought to relax accommodation?

sympathetic innervation

What is the maximum motor output of the accommodative system known as?

amplitude of accommodation

What are the two methods to determine amplitude of accommodation?

Donders Push up
Minus Lens Blur

How is facility of accommodation measured?

Plus-Minus Flippers
Far-Near

True or False,
For most patients, the accommodative response is greater than the stimulus to accommodate.

False most have a lag not a lead

What is the expected lag of accommodation?

1/2 to 3/4 a diopter

What are four tests of posture of accommodation?

MEM
Nott
FCC
UFCC

What effect do minus lenses have on accommodative vergence?

Minus lens induce accommodation, increase accommodative vergence and result in an eso deviation

What effect do plus lenses have on accommodative vergence?

Plus lens reduce accommodative vergence because they relax accommodation and therefore result in an exo deviation

What is a test that measures accommodation for computer users?

the PRIO System

What condition includes a high lag and can respond well to VT?

accommodative insufficency

What condition of accommodation is characterized by a lead of accommodation and is harder to treat with VT?

accommodative excess

The inability to shift accommodation rapidly is know as _____?

accommodative infacility

What are three common conditions that will present with errors in the accommodation system?

Eccentric Fixation
Amblyopia
ET

What do the high level cortical processes control in saccades?

target selection
calculation of eye position
modifies the final signal

What do lower level cortical control processes control in saccades?

the structures involved in the actual pulse step signal- the ocular motor neurons

What structures control when to generate a saccade?

cortex and the superior colliculus

What do the frontal eye fields and parietal lobe do during saccades?

They receive information about where to move the eyes and pass it to the superior colliculus

What is the primary function of the frontal eye field during saccades?

select the targets for future foveation

The frontal eye fields are associated with (voluntary/involuntary) saccades?

voluntary

What is responsible for involuntary or reflex saccades?

The posterior parietal cortex, POT jxn

A lesion in the FEF or the POT junction will have what effect on saccades?

slowed saccades
increased latency
impaired tracking

What acts to calibrate saccades?

cerebellum

What does the superior colliculus do in saccades?

processes information form the FEF, encodes the desired change and then sends it to the brainstem

Where do superior colliculus projections terminate?

the PPRF

The amplitude and direction of a saccade information is sent from what structure?

the parietal lobe

Lower level processing of in the saccade is the synchronization of what two elements?

Burst and pause neurons

Burst Neurons in the PPRF are responsible for what type of saccade?

horizontal

Where do burst neurons reside?

PPRF and riMLF

Where are pause neurons located?

nucleus raphe interpositus

What is the role of the excitatory burst neuron?

they generate the pulse signal just before and during the saccade

What is the role of the inhibitory burst neuron?

they inhibit the antagonist muscles

The pulse signal is the peak________ of a saccade?

velocity and amplitude

When do pause neurons fire?

in the absence of saccades, ie during fixation

What is the key function of the pause neuron of the saccade?

they allow the saccade to occur, only after the pause neurons are inhibited can the burst neurons activate

What neurons produce the step signal?

tonic neurons

Where are tonic neurons located?

in the nucleus prepositus hypoglossi (NPH)

What happens at the NPH during a saccade?

the burst signal is integrated to step signal

What are four classes of saccades?

Volitional
Reflexive
Spontaneous
Quick Phases

What type of saccade is used attend to a remembered location, to command, or to perform an antisaccade?

volitional

When are quick phase saccades performed?

VOR and OKN

What are four reasons that saccades may have reduced velocity?

Meds side effects
Myasthenia Gravis
Peripheral Nerve Palsy
Darkness

Inaccurate saccades can likely be traced to what area for a pathology?

cerebellum

Why can one predict that parkinsons disease will affect saccades?

because the substania nigra is primarily affected and it projects to the superior colliculus

What saccadic test is used in dementia patients?

antisaccade test

What patients will have marked difficulty in the antisaccade test?

frontal lobe lesions
Huntingtons disease
alzheimers

What is the super imposition of unlike targets?

first degree fusion

What is second degree fusion?

Fusion of targets that have like contours

What is also known as flat fusion or fusion without depth?

second order

What is the third degree of fusion?

stereopsis

What two things will the visual system use if two images can't be fused?

Anamalous retinal correspondence or suppression

If a strabismic patient suppresses what are the states of his motor and sensory fusion?

both are bad

If a strabismic patient uses anomalous correspondence to compensate what is the state of his motor and sensory fusion?

motor is bad but sensory is good

The theory that two monocular views will mutually inhibit each other is called what?

Alternation theory of fusion or the suppression theory

An example of the alternation in the alternation theory is_____

binocular rivalry

When does alternation occur?

when grossly dissimilar objects are presented to each eye

What is horror-fusionalis?

the inability to maintain sensory fusion

Images that are formed on corresponding retinal points are seen as________?

single

True or False
Only images that fall on corresponding points can be fused to a single image?

False

What is the region around the horopter that allows single vision?

Panum's Fusional Area

Panums fusional area size is measured in what?

minutes of arc

The magnitude of fixation disparity cannot exceed __________ if one is to maintain single vision?

Panums Area

True or False
Panums Fusional Area is larger vertically than horizontally?

False- 3-6X larger horizontally

What is the size of PFA at the fovea?

5 to 20 moa

What is the relationship between low temporal and spatial frequencies and PFA?

they both allow for a larger PFA

High temporal and spatial frequencies have what effect of PFA?

they both cause a reduction in PFA

What three things allow for a large panums fusional area?

peripheral retina stimulation
low spatial frequency
low temporal frequency

What is Utroclur discrimination?

the ability to determine which eye has been stimulated

True or False
Humans cannot make untrocular discriminations?

true- monocular information is lost

What is dichoptic stimulation?

presenting targets to each eye independently

What are two clinical applications dichoptic stimulation?

binocular refraction and testing suppression

What is responsible for the maintenance of binocular vision in the presence of a phoria?

motor fusion

When will fixation disparity be seen as single?

when it is inside panums fusional area

How many MOA equal one prism diopter?

approx 40

A clinical measurement of a fixation disparity will have what two parts?

a binocular fusion lock and two nonius lines

What are some clinical tests to measure fixation disparity?

Wesson Card
Sheedy Disparometer
Borish Card
Bernell test Lantern
Vectographic slide

What is the distances used for the bernell test lantern?

distance and near

The borish card is used only at what distances?

near and intermediate

On a wesson card if the bottom line is seen to the right of the top line it is consistent with what type of deviation?

Exo

How long can the fast fusional system maintain control?

about one second

What activates the fast fusional system?

retinal disparity

True or False
A patient that presents with prism adaptation does not have a healthy vergence system

false, PA is a sign of a good vergence system

Describe a fixation disparity curve type I?

Sine wave with a flatter central region and steeper peripheral, most patients

What is a type II fixation disparity curve?

doesn't cross into the exo portion, 20 to 25 percent of pts, most are esophoria, highly adaptive to base out prism

What is a type III fixation disparity curve?

doesn't cross into the eso portion, about 10 percent of patients, most likely exophoric

WHat is a type IV fixation disparity curve?

small flat sine wave, no phoria, possible anisokonia

What are the effects of vision therapy on the FD curve?

flattens the slope

Which patient will be more likely to be symptomatic on the FDC on with a flatter or steeper slope?

Steeper

What is a good starting point for prism prescription from the FD curve?

1/2 the associated phoria

What is the point at which the FD curve crosses the Y axis?

fixation disparity

What is the x intercept in the FD curve?

associated phoria

The ability of a visual neuron to process direction is referred to as?

local sign

Where are local signs referenced to?

the fovea

What is the fovea's local sign?

principle visual direction

What is the neurological remapping where the PVD is no longer defined by the fovea, involuntarily?

eccentric fixation

What is the difference in eccentric viewing and eccentric fixation?

in viewing the fovea is still in control of PVD but in EF a new spot is reassigned to be the fovea

What is the egocenter or cyclopean eye theory?

that under binocular conditions we see directions relative to a single point within our head

Two points lying on the Vieth-Muller circle should be seen as_______?

single points without depth

Points nearer than the vieth-muller circle will result in what?

crossed diplopia

Points distant to the vieth-muller circle will result in what?

incrossed diplopia

Objects that don;t stimulate corresponding points are said to be?

disparate points

How much binocular disparity is perceived by corresponding retinal points?

zero

Horizontal binocular disparity allows for the perception of what?

stereoscopic depth

What is the spatial map of all corresponding retinal points?

Horopter

Objects located on the horopter fall on _______ points?

corresponding

What theory states that all corresponding points are evenly spaced with equal angles relative to the PVD?

Vieth-Muller

What are the methods for measuring the horopter?

AFPP aka stereoscopic matching
Haplopic
Nonius Horopter

What is more curved the horopter or the Vieth-Muller circle?

the Vieth-Muller circle

The distance between the Horopter and the VM circle?

Hering-Hillebrand Deviation

At a point H>0 where is the horopter in relation to the V-M circle?

outside

At a point where H<0 where is the horopter in relation to the V-M circle?

inside

What are three things that can effect the shape of the horopter?

Fixation Disparity
Viewing Distance
Anisokonia

At greater fixation distances the horopter becomes_______?

convex

At near fixation the horopter is_____?

concave

What is the Abathic distance?

The point where the perceived horopter is equal to the actual horopter

If the right eye image is larger what direction is the horopter moved towards?

toward the left

What is the direction of the vertical horopter?

top tilted away from the viewer

What direction does the horopter move in the presence of BO prism?

bows away from the observer

What direction does the horopter move in the presence of BI prism?

Horopter bows towards the observer

What is Flom's notch?

it is the notch of the horopter in some constant ET

What vergence is the difference in the anatomical position of rest and the physiological position of rest?

tonic vergence

What is also known as dark vergence?

Tonic Vergence

What is the clinically estimated measure of tonic vergence?

Distance Phoria

What is also known as psychic vergence?

proximal vergence

At what point does proximity begin to influence vergence?

3 meters

How is disparity vergence removed from the system?

occlude or prism

How is accommodative vergence system removed to measure proximal vergence?

use of a pinhole

Under an open loop condition how much can proximal vergence alter convergence

up to 40 percent

What is the effect on the target perception with increasing base out prism?

appears to be smaller and closer

If the target is percieved to be outside the intended target it appears?

larger

What does SILO stand for?

Small in Large out

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