8- Therapeutic Perceptual Learning Flashcards by Anya Laila

Amblyopia is also known as?

lazy eye

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Which condition is described by the following:

Poor (‘blunt’) vision in one eye caused by disruption of normal visual input during the critical periods

Most common causes of monocular vision loss in children

Developmental disorder of vision that affects 2-4% of the population

Neural locus of primary deficit in primary visual cortex

Amblyopia

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Amblyopia (lazy eye) has an origin issue which is not in the eye but at levels of the what?

Neural locus of primary deficit in primary visual cortex

(should be lazy brain not eye)

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Which condition is the common causes of monocular vision loss in children?

Amblyopia (lazy eye)

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What is Amblyopia commonly associated with?

Strabismus - misalignment of visual axes

Anisometropia – unequal refractive error (1 of the eyes has very poor visual acuity compared to the other)

Leads to binocular and stereo dysfunction

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Which disorder is known as the misalignment of visual axes?

Strabismus

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Inter-ocular suppression and amblyopia:

In normal vision, object of interest is imaged on corresponding points on the two retinas and fused for binocular vision

In amblyopic vision, suppression ’switches off’ vision in the deviating eye preventing signals reaching conscious awareness

In amblyopia (with strabismus), object of interest is imaged on non-corresponding points on the retinas in the two eyes. One affected eye aligns with fixation point and the object falls within the fovea, but other eye will apear to have a misaligned object in its fovea

What 2 things does this lead to?

Confusion:
Something other than object of interest is imaged on fovea of deviating eye

info from the 2 eyes in the same spatial location is different leading to confusion as the brain does not know what to do

Diplopia:
Object of interest imaged on non-foveal part of retina in deviating eye

info (object) falls in the fovea within one of the 2 eyes, due to missalignment it falls in a slightly different position on the retina, now its the same representation of the object but in 2 different locations (double vision)

Images on foveas in deviating and non-deviating eyes are dissimilar and cannot be fused

Weakest eye info is suppressed = Inter-ocular suppression

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Which disorder is known as the unequal refractive error (1 of the eyes has very poor visual acuity compared to the other)?

Anisometropia

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What is the term to describe the brain suppressing info from the weakest one of the 2 eyes when seeing double vision in those who have amblyopia (with strabismus)?

Inter-ocular suppression

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Inter-ocular suppression and amblyopia:
What does this describe?

Something other than object of interest is imaged on fovea of deviating eye

info from the 2 eyes in the same spatial location is different leading to confusion as the brain does not know what to do

Confusion

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Inter-ocular suppression and amblyopia:
What does this describe?

Object of interest imaged on non-foveal part of retina in deviating eye

Diplopia

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History of the treatment for amblyopia:

Who developed masks to correct the deformed vision or strabismus to try and force individuals to align their eyes?

George Bartisch (1535-1607)

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History of the treatment for amblyopia:

Who was the first to describe the use of occlusion therapy for stronger eye until vision in strabismic eye returns to normal?

Thabit ibn Qurrah ibn Marwan al-Harrani (836-901)

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History of the treatment for amblyopia:

Who used the term ‘amblyopia’ to describe diminished acuity in healthy eyes and treated it with oil, vinegar, water, minerals and dietary alterations?

Hippocrates (~480 BC)

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History of the treatment for amblyopia:

De Buffon (1743) – usually credited with introducing occlusion therapy for the treatment of amblyopia (eye patches)
Child is given an eye patch on their good eye, to try and make they bad eye realign with good visual acuity again.
-frontline treatment for amblyopia

What are the limitations of this treatment still used today?

Limitations: A03

-Major limitation of occlusion therapy is compliance in wearing the patch, Distressing for the child, unpopular with parents and children (c.f. atropine penalization)

-Only 50% of children achieve normal vision in the amblyopic eye after occlusion therapy.

-Long periods of occlusion can lead to binocular vision problems for the good eye, such as reduced stereopsis

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Compliance is poor and residual amblyopia is common due to what?

treatment failures and slippage

Refractive correction and amblyopia: info slide

Good evidence that corrective spectacles should be used before occlusion

Refractive correction typically used for 12-16 weeks and can cure amblyopia in children if the acuity deficit is not too deep

Occlusion therapy should only be used after the benefits of refractive correction have reached plateau

Providing glasses with different lenses to individuals
Part-time is as effective as full-time occlusion therapy

Part time occlusion (2-6 hours/day) is as effective as patching the eye for entire day

Slippage after treatment cessation

Patching the … eye to encourage use of the … eye is the frontline treatment for amblyopia in childhood?

non-amblyopic, amblyopic

-Occlusion therapy for amblyopia has remained largely unchanged for more than 250 years

Monocular perceptual learning as a treatment of amblyopia:

To try and improve visual acuity in the amblyopic eye (bad eye)

Adults with amblyopia demonstrate substantial and significant…

perceptual learning of Vernier acuity

discrimination tasks are important for visual acuity improvement

info:
All amblyopic subjects improved their performance on the Vernier acuity task
Learning partially transferred to untrained orientation and eye, but not an untrained line detection task
Critically, in some subjects learning on the Vernier task transferred to and improved Senellen (letter chart) acuity

Amblyopia is/ is not conventionally treated in adulthood

is NOT

What are the two approaches to perceptual learning in adult amblyopia?

Learn to improve the visual quality of the representation in the amblyopic eye (e.g. Dennis Levi)

Learn to reduce inter-ocular suppression of amblyopic eye (e.g. Robert Hess)

-Improve the visual acuity and contrast sensitivity deficits in the amblyopic eye

-Closely match the size and clarity of the cortical visual representation of input from the two eyes

-Learn on binocular and stereo acuity tasks to optimise stereo vision

describes which approach to perceptual learning in adult amblyopia?

Learn to improve the visual quality of the representation in the amblyopic eye (e.g. Dennis Levi)

(Start immediately)

Learning can recover stereo vision in adult amblyopia:

Two adult amblyopic subjects (with anisometropia) were trained on their visual acuity. They learned a monocular acuity task to reduce the difference in visual acuity between the two eyes

After monocular learning, they demonstrated gross stereopsis on a standard clinical test of stereo acuity. What does this mean

Gross stereopsis:

They began to see and discriminate things in depth.

They both trained on a stereoscopic task, which improved their stereo acuity to near-normal levels
The learned improvements in stereo acuity were retained 7 months after the cessation of training

-Improve the combination of visual signals by the two eyes

-Learn on binocular tasks that break suppression of the amblyopic eye by the non-amblyopic eye

-Improve binocular fusion and stereopsis; acuity improvements in the amblyopic eye are a secondary benefit

describes which approach to perceptual learning in adult amblyopia?

Learn to reduce inter-ocular suppression of amblyopic eye (e.g. Robert Hess)

(improve visual acuity in the amblyopic eye)

Monocular perceptual learning as a treatment of amblyopia: Trained adult amblyopic subjects on contrast detection task with and without flankers

They found a two-fold improvement in contrast sensitivity Learning on contrast sensitivity also improved over time for untrained visual acuity Learning retained for at least 1 year after the cessation of training

During childhood there is a sensitive plasticity period of rewiring and helping correct visual acuity. The expectation is that if you don't intervene while in or before this critical period then you cannot correct vision problems. But this is not true (residual plasticity) What is a way to enhance plasticity in later life?

In childhood there is higher neural plasticity, but in adulthood there is residual plasticity Removing these breaks: in childhood there are some neural mechanisms which prevent your neural plasticity from coming into action

Binocular perceptual learning as a treatment for amblyopia: Study used binocular motion coherence task in which they presented dots moving in a coherent direction (signal) to one eye and dots moving in random directions to the other eye (noise). During training, they repeatedly measured motion coherence thresholds, while manipulating the relative contrast (strength) of signals to the two eyes to weaken suppression of the amblyopic eye by the non-amblyopic eye. What were the findings?

With enough training: -some amblyopic subjects needed less motion signal in their amblyopic eye to perform the motion coherence task -the inter-ocular contrast ratio was altered indicating a change in suppression Binocular training: -reduced the acuity deficit in the amblyopic eye and consequently the difference in acuity between the two eyes

Binocular perceptual learning as a treatment for amblyopia: What does Binocular training do?

It reduces the acuity deficit in the amblyopic eye (wonky eye) and the difference in acuity between the two eyes -can produce a small improvement in the stereo acuity of most of the amblyopic subjects -can improve visual function in amblyopia by reducing inter-ocular suppression

What are the two approaches to implementing learning protocols?

Deficit-driven Outcome-driven

Which approach to implementing learning protocols does this describe: 1- Understand the visual deficit 2- Optimize learning protocols on psychophysical tasks in the laboratory 3-Incorporate learning principles into digital technology (e.g. video game) for treating visual deficit

Deficit-driven

Which approach to implementing learning protocols does this describe: 1-Use off-the-shelf digital technology (e.g. video game) 2-Optimise learning protocols on the digital technology 3-Measure and interpret visual outcomes of learning on the digital technology

Outcome-driven

Deficit-driven approaches to treating amblyopia incorporate scientific principles developed in the laboratory into therapeutic digital devices. give an example:

video games

Outcome-driven therapeutic learning in amblyopia:

Repeated practice on video games (action and non-action) produced a 33 % improvement in visual acuity Stereopsis improved by 54% after repeated practice of the video games All improved better over time of playing

Incorporating binocular learning principles into a video game: Outcome-driven learning Researchers incorporated the principles of binocular learning developed in the lab into a Tetris game for the ipod touch Tetris blocks presented to fellow eye are low contrast (e.g. static blocks) and Tetris blocks presented to the amblyopic eye are high contrast (e.g. falling blocks) What type of video gamers had enhanced contrast sensitivity at at intermediate and high spatial frequencies compared to control and trained groups?

Action video game players Playing video games results in enhancement of a broad range of other visual tasks in adults with normal vision, including light sensitivity, visual crowding and visual attention

Which type of treatments provide a better understanding of the effects of the visual deficit and learning in amblyopia?

deficit-driven treatments But it is not yet clear yet which approach will deliver most benefit for visual enhancement or visual quality of life in adults with amblyopia

Outcome-driven approaches measure and interpret visual outcomes of learning on off-the-shelf what?

digital technology