BV: Supression Flashcards by Bella Forster

Stereopsis

Responsiveness to disparate retinal stimuli

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Suppression

Active cortical inhibition resulting in the loss of awareness of visual impression for one eye in binocular vision

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Type categories of suppression

Pathological or physiological

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Pathological suppression most often occurs in patients with what?

Strabismus or anisometropia amblyopia

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Pathological suppression can also occur in these patients (but less often seen)

Aniseikonia and poorly compensated heterophoria

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What is suspension?

Physiological suppression

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Physiological suppression occurs in all patients is considered part of what?

Normal, single binocular vision

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When binocular fixation is maintained at a fixed distance, objects that are closer or farther away are imaged on ___________retinal regions and are NOT located within __________

Non-corresponding retinal regions

Not located within panums fusional area

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What happens when two dissimilar patterned images are simultaneously presented onto the fovea?

The brain suppresses on of the two images

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What happens to the images of objects when one of the two eyes is deviated?

The images of the objects are physically separated in space and are dissimilar is size, shape, and orientation and are placed onto corresponding fovea causing visual confusion

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What happens in visual confusion?

Two dissimilar images are seen as being superimposed and projected to the same point in space

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Why is visual confusion rarely reported?

Because we experience retinal rivalry

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Who exhibits pathological suppression most often?

Strabismus or anisometropic amblyopia patients

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What occurs in a strabismus?

Retinal rivalry is lost and is replaced by suppression of the deviating eye

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When will/does diplopia occur?

When images from a. Single object fall on non-corresponding points that are too disparate for the visual system to fuse

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Uncrossed diplopia, where does the images fall and where is the eye projected?

Image falls on the nasal retina in the esotropic eye is projected temporally

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Crossed diplopia, where does the image fall and where is the eye projected?

Temporal retina and the eye is projected nasally

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What is seen in patients with an early onset strabismus?

Suppression has developed so they do not have diplopia

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Do Patients with strabismus suppress the entire retina of the deviating eye, or just a portion of it?

Typically just a portion or zone of the deviating eye

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What is the diplopia point/zero measure point, or point “z” ?

The peripheral area of the deviated eye where suppression must exist to eliminate the diplopia

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When would the patient be considered monocular in regard to suppression?

When the suppression zone encompasses both the fovea and the zero measure point

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Where is the zero point in a esotropia typically?

Peripheral suppression in the nasal hemiretina

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What zone of suppression (shape) is formed in an esotropia?

Elliptic D-shaped zone

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Is the depth of the suppression uniform in an esotropia?

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Where is the suppression more intense in an esotropia?

At the zero-measure point and at the fovea

The size of the suppression zone in an esotropia is proportional to what?

The size of the deviation

Exotropia supression zone involves what?

Majority and if not all of the temporal hemiretina REGARDLESS of the deviation size

Esotropia suppression Zion’s includes supression of the _____ hemiretina

Nasal

Exotropia suppression zone includes supression of the _____ hemiretina

Temporal

How can we measure the supression zone?

Use prism of increasing power

Prisms move the image where?

Out of the patients supression zone

3 supression zone areas

Peripheral Central Foveal

Shallow deviation

Suppression presents but diplopia or sensory fusion still occurs

Deep deviation

Supression continues to occur without diplopia or sensory fusion

In unilateral strabismus, what suppression is seen?

Monocular suppression always in the deviating eye

How is suppression in an alternating strabismus?

Suppression occurs only in the deviating eye, but it can alternate eyes

Suppression only occur when the eyes are misaligned with ______ strabismus

Intermittant

Supression only occurs in th exposition of faze in which the strabismus occurs with ______ strabismus

Incomitant

What is the most effective stimulus to elicit strabismic suppression?

Contours of similar shape, color, and orientations

The more dissimilar the images on non-corresponding retinal points, the _____ likely the patient is to be suppress

Less likely to suppress

Onset of suppression latency

75-150ms

Suppression develops only in what patients?

Visually immature

Approximately what percentage of children with strabismus suppress?

100%

If an adult acquires a strabismus , will they suppress?

Likely no

The absence of diplopia in a patient with strabismus does not always imply suppression has developed. Some patients that develop strabismus later in life learn to do what instead?

Disregard the diplopia image —> visual ignoring

What types of amblyopia can suppression occur in?

Strabismic or refractive amblyopia

Deeper the amblyopia = _____ need for strong suppression of that eye

Less need

Shallow amblyopia often have the ________ suppression

Strongest

What is horror fusionis?

The inability to obtain binocular fusion or superimposition of targets, an active aversion to fusion

Horror fusionis is associated with what?

Intractable diplopia

What is the most common treatment for horror fusionis?

Occlusion using spectacle blur or contact lenses

Suppression of the temporal hemiretina occurs in ________

Exotropia

Describe esotropia suppression zone

Smaller in size and proportional to the size of the deviation

Deep suppression

Suppression that continues to occur without diplopia or sensory fusion

What is the traditional test and one of the most commonly used and accurate tests for suppression?

Worth 4 dot

W4D assesses ________ fusion at distance and near

Second degree (flat)

What does the patient wear in W4D testing?

Red-greeen glasses (red over OD)

In W4D testing the eye witht the green lens sees the ______dots , and the eye with the red lens sees the _______ dots

Green, red

W4D should be recorded in one what what 3 ways?

Fusion Diplopia Alternating or unilateral suppression with location

As the W4D is moves away from the patient, the target subtends a _____ angle on the retina

Smaller angle

If a patient suppresses at 33 cm, this suggests a ______ scotoma The target will project approximately a 6 degree area of the retina -> testing ______ fusion

Large Peripheral

If a patient suppresses at 6 meters, this suggests a _____ scotoma The target will project approximately a 1.5 degree area -> testing ______________ fusion

Smaller Bifoveal or macular

W4D testing includes quantifying the exact ______ that the patient begins suppressing

Distance

If a patient reports 4 dots at 33cm but 2 dots at 4 meters in light only, what does this tell you about their suppression zone?

Suppression zone OS is somewhere between 1.5 and 6 degrees in diameter and its intensity would e considered shallow

What room illuminatin is more likely to show suppression in W4D testing?

Normal lighting

Suppressing in light ONLY suggests a ______ suppression, while suppressing in dark conditions suggests ______ suppression

Shallow suppression Deep suppression

If suppression is present, tell the patient to cover the eye that is not suppressing and ask if the suppressed dots reappear. Reappear = suppression scotoma only under _____ conditions Do not reappear = _______ scotoma

Binocular scotoma Unilateral scotoma

Some clinicaians will utilize W4D to determine the amount of prism necessary to obtain ______ fusion and use this in prescribing

Sensory fusion

What test is the least dissociating method of measuring prism?

Bagolini striated lenses

Striations on bagolini lenses produce a luminance streak _____ when the patient views a point source of light

Perpendicular (90 degrees away)

Bagolini striated lens striations are placed at _____ and ______ degrees

45 and 135 degrees

How are the room lightss when performing bagolini striated lenses?

Dimmed

Where is the transilluminator help and what is the patient asked to report in bagolini striated lenses procedure?

Held at 20 feet and 40 cm Report the presence or absence of lines

Bagolini normal result

Lines will intersect at the point light source forming an X

Bagolini results when suppressing one eye

There is a gap in the streak or complete loss of the streak

What does the total suppression result in when doing bagolini striated lens testing?

One of the streaks will be absent

Bagolini filter bar helps to determine what?

The depth/intensity of the suppression with a persons strabismus

What is depth of suppression?

How easily can a patient break or overcome their suppression

When is suppression shallow when testing with bagolini filter bar?

If the image of the white light is elicited very quickly with a very light red filter

When is suppression deep when testing with the bagolini filter bar?

If the image of the white light is elicited only after the illumination of the dominant eye is greatly reduced —> dark = deep

When is the prognosis for achieving normal binocular vision better?

When suppression can easily be broken

What is a synoptophore also known as?

Amblyoscope

What does a synoptophore test?

Sensory fusion and suppression

What targeted placed in the viewing tubes in a synoptophore?

Large 1st degree targets

What degree targets are the hardest to suppress?

1st degree

What degree targets are the easiest to suppress?

3rd degree

Look at the degrees of fusion on slide 68

…

Are the following targets easier or harder to suppress: -Larger, peripheral targets -1st and 2nd degree targets -Moving target -Bright target -High contrast target

Harder to suppress

Are the following targets easier or harder to suppress: -small, central -3rd degree targets -stationary target -dim target -low contrast target

Easier to suppress

Prism may be used to test suppression, we can presume that the patient will recognize the diplopia when the prism causes the image to do what?

Fall outside the limits of the suppression zone

What is the 4 base out test?

A test used to detect small central scotoma and/or confirm suppression in cases of unexplained amblyopia and/or reduced stereopsis when result of cover test is ambiguous

Which eye do you place the 4 base out prim in front of? And what are you looking for?

Place over the better seeing eye Looking at both eyes for movement

What is a normal response in a 4 base out test?

Prism is placed in front of the eye results in a VERSION movement of BOTH eyes followed by a refixation or Vergence of the eye without prism

BV: Supression Flashcards

(93 cards)