Brain damage-related Vision Loss – Functional Classification



(Slide 1 – Title Slide)

Functional Classification

of

Brain Damage-related

Vision Loss

CVI – CVD – TBI – CVA

CVI Workshop – AFB-JLTLI April, 2008

August Colenbrander, MD - San Francisco

Presenter’s Notes

We have heard about the many ways in which cerebral disorders can affect visual behavior. I have been asked to speak about their functional classification.

(Slide 2)

ASPECTS Of VISION LOSS

Three Objects ?

Slide Graphics

Drawing of three shapes; triangle, square, and circle

Presenter’s Notes

To do so, we must look at different aspects of vision and vision loss. What do we mean when we speak of aspects? Let me give an analogy. Do you see three objects here?

(Slide 3)

Three Objects?

Slide Graphic

Similar drawing to graphic in Slide 2, but now there are objects placed over the drawings. They represent a cone for the triangle, a cube for the square, and a ball for the circle.

Presenter’s Notes

Or could it be that you are just looking at three aspects of an unfamiliar object?

(Slide 4)

Different Aspect – Same Object

Slide Graphic

Drawing of an object that first appears within the outline of the triangle. The second drawing is of the same object being rotated on its vertical axis. The third drawing is of the object rotated and appearing inside the square outline drawing.

Presenter’s Notes

Turning the object around to look at it from different view points, we see that what seemed different objects may just be different aspects of the same object.

(Slide 5)

Aspects

Reveal properties of the object

they also

Reveal the point of view of the beholder

Presenter’s Notes

I like the concept of ASPECTS, because it informs us not only about properties of the object, we also gain insight in the point of view of the beholder.

(Slide 6)

ASPECTS of an Office Visit

Patient with AMD . . .

Front desk: When can I schedule?

Doctor: PDT or Avastin?

Manager: Will insurance pay?

Daughter: Can mother still drive?

Presenter’s Notes

Consider a patient with AMD, who comes to make an appointment. The front desk will think about when to schedule her. The doctor will think about which treatment to select. The office manager may worry whether the insurance may pay. The daughter worries whether mother can still drive. Those are all very different aspects of the same clinical case.

(Slide 7)

Aspects of Visual Functioning

Slide Graphic

Diagram containing two major headings: The Organ (on the left side) and The Person (on the right side). Each of these headings has subheadings underneath that are displayed in rectangular boxes. A right point arrow appears between each of these boxes indicating a direction of flow. Four of these subheadings also have subheadings and several points listed under each. They will be listed below in an outline format. The final subheading and the list appear as the presenter talks about each point.

The Organ

Cause

Structure

Tissue

Scar

Atrophy

Loss

Photograph of a man preparing to look through a microscope

Function

Organ

Acuity

Field

Contrast

Photograph of an eye care specialist testing a patient’s visual acuity with an eye chart.

The Person

Ability

Person

Reading

Mobility

ADLs

Photograph of a woman using a hand-held magnifier to read.

Consequences

Society

Participation

Quality of Life

Photograph of a woman knitting.

Presenter’s Notes

Similarly, depending on our point of view, we can consider many different aspects of vision loss when we discuss visual functioning. First we may consider how various causes may result in structural changes at the organ level, such as scarring, atrophy or loss. Here we need the pathologist to look at the structure of the organ.

However, the structural changes do not tell us how well the eye can function. We need to widen our view to include functional changes, and measure aspects such as visual acuity, visual field and contrast sensitivity.

Knowing how the eye functions, does not tell us yet how the person functions. So we need to widen our perspective again to consider tasks, such as reading, mobility, face recognition. Here we need various low vision professionals to work with the patient, in this picture an elderly patient with macular degeneration.

Beyond that, we need to look at the consequences in a societal context. Do these changes impact on the person’s participation in society, causing job loss or reduced quality of life? How can we be sure of a happy patient, which is the end goal of all our interventions?

(Slide 8)

Aspects of Visual Functioning

Slide Graphic

This slide uses the same diagram as in Slide 7. The photographs have been removed and two other points have been added at the bottom. A vertical line has been inserted to separate the Organ side from the Person side.

The Organ

Cause

Structure

Tissue

Scar

Atrophy

Loss

Function

Organ

Acuity

Field

Contrast

VISUAL FUNCTIONS – How the EYE functions

The Person

Ability

Person

Reading

Mobility

Face recognition

Consequences

Society

Participation

Quality of Life

FUNCTIONAL VISION – How the PERSON functions

Presenter’s Notes

For today's discussion it is useful to draw a line in the middle; on the organ side we speak of visual functions, on the person side of functional vision.

(Slide 9)

Aspects of Reading

Slide Graphic

This slide uses the same basic diagram used in Slide 7. The item Reading under The Person, Abilities, has been moved down to use as an example. There are three additional points pulled out from this item: Print size, speed; Reading endurance; and Reading enjoyment.

Presenter’s Notes

Various activities may cover more than one aspect. When we consider READING, the measurement of print size and reading speed belong in the organ function column. Yet, it is not only important how many words per minute we can read, but also how many hours per day. Reading endurance belongs in the ability column. Reading enjoyment, finally, belongs with the aspect of Quality of Life.

(Slide 10)

Traditional Medical Focus

Slide Graphic

This slide uses a similar diagram to the one used in Slide 7. It contains the two large headings; The Organ, and The Person. It also contains the subheadings with the arrows connecting them.

The Organ

Cause – Structure – Function

The Person

Abilities – Consequences

Under The Organ side of the diagram an additional point has been added.

MEDICAL FOCUS

How do anatomical changes affect visual functions?

Presenter’s Notes

The traditional medical focus is on the organ of vision, its structure and its functioning.

(Slide 11)

Rehabilitation Focus

Slide Graphic

Similar diagram to Slide 10. Medical Focus is replaced with

FOCUS ON REHABILITATION

How do changes in the EYE and in the BRAIN affect functional vision?

Presenter’s Notes

The rehab focus extends this to the functioning of the person.

(Slide 12)

Traditional Medical Focus

Slide Graphic

Continued use of same diagram as before with the two major headings and the five subheadings. The subheading Structure under The Organ has an additional point underneath it with several sub-points which will be listed in outline format.

CAUSES of Vision Loss

Anatomical classification

Ocular

Optical

refractive error

opacities

Retinal

scars

dystrophies

Cerebral

Pathways

Lesions

PVLM

Cortex

Lesions

amblyopia

Presenter’s Notes

For the traditional focus on the causes of CVI, we need an anatomical classification. We consider eye conditions, which can involve either the optics or the retina. We also consider cerebral conditions, which can involve either the pathways or the cortical structures. That cerebral causes can involve more than just the cortex is a clear reason why we should speak of CEREBRAL, rather than CORTICAL visual impairment.

(Slide 13)

Consequences of Vision Loss

Slide Graphic

Continuing with same basic diagram. The subheading Function under The Organ has a new sub-point.

VISUAL FUNCTIONS

Standardized Measurement of

Visual Acuity

Contrast Sensitivity

Visual Field

Cognitive problems

how to define

how to measure

Presenter’s Notes

To discuss the consequences of CVI we need a functional classification. That will be my topic. In the area of VISUAL FUNCTIONS, we have good standardized methods to measure things such as Acuity, Field and Contrast Sensitivity. We need to extend that to the area of cognitive dysfunctions. We need to define the problems and standardize the assessment.

(Slide 14)

Consequences of Vision Loss

Slide Graphic

Same basic diagram. The Abilities subheading under The Person has a new sub-point.

FUNCTIONAL VISION

Visual Communication

Activities of Daily Living

Orientation and Mobility

Sustained Near Vision

Cognitive problems

Presenter’s Notes

In the area of the ABILITIES of the person, we can look at the four categories promoted by Lea Hyvärinen. We again need to look in more detail at cognitive problems for each activity.

(Slide 15)

The Visual Process

Slide Graphic

The same basic diagram, similar to the one in Slide 8 in that it has the two major heading, The Organ and The Person with the first level of subheadings; Cause, Structure, Function under The Organ, and Abilities, Consequences under The Person. The vertical line is present again separating the two major headings. The following items are listed under The Organ side.

VISUAL FUNCTIONING – how the VISUAL SYSTEM functions

Defects: VISUAL IMPAIRMENT

Refers to lower visual functions with retinotopic organization

Items listed under The Person side

FUNCTIONAL VISION – how the PERSON functions

Defects: VISUAL DYSFUNCTION

Refers to higher visual functions with conceptual, cognitive organization

Presenter’s Notes

Going back to the earlier distinction between visual function and functional vision, we use the tem VISUAL IMPAIRMENT to indicate deficits in how the eye and the visual system function. I prefer to use the term VISUAL DYSFUNCTION for deficits in functional vision. I prefer these separate terms to emphasize the differences in approach.

At the cerebral level, visual impairments deal with lower visual functions, mainly in retinotopically organized cortical areas. Visual dysfunction refers to higher visual functions in areas with conceptual and cognitive organization.

(Slide 16)

The Visual Process

Slide Graphic

Same basic diagram as in previous slide with new information under the Deficits points.

Deficits: VISUAL IMPAIRMENT

Lower visual functions

Tests use a variable stimulus to obtain a constant response

(threshold, 50% correct)

Deficits: FUNCTIONAL VISION

Higher visual function

Tests use a fixed task and record a variable response

(sustainable performance, must be > 50%,)

Presenter’s Notes

The assessment of the two areas is very different. On the impairment side, we typically test one parameter at a time, in an artificial environment.

We record the stimulus level that results in a fixed endpoint: the threshold level, where the responses are 50% correct.

On the dysfunction side, we present a fixed task and record the variable performance of the subject. That performance must be at a sustainable level, which always is well above 50% correct.

(Slide 17)

Tests - One Parameter at a Time

Slide Graphic

Three photographs of familiar threshold tests: Visual Acuity Threshold, Contrast Sensitivity Threshold, and Dark adaptation Threshold.

Presenter’s Notes

Here I show three familiar threshold tests, each measuring a different parameter. Visual acuity, contrast sensitivity and dark adaptation. Each test varies only one parameter at a time.

(Slide 18)

Real Life – Multiple Parameters

Need for SUSTAINABLE performance

Slide Graphic

Photograph taken from inside a boat looking over a woman’s shoulder as she looks out of a window at the approaching scenery. The photo illustrates the variation in details, contrasts, and illumination found in most real world scenes.

Presenter’s Notes

In real life, however, we always have to deal with multiple parameters. Detail varies, as does contrast, as does illumination. Furthermore, we ask for sustainable performance.

(Slide 19)

Stages of Visual Functioning

Slide Graphic

Diagram divided into two vertical sections: VISUAL FUNCTIONS; how the EYE functions, and FUNCTIONAL VISION; how the PERSON functions. There are three stages that will be discussed.

OPTICAL STAGE

Provides clear optical image on the retina

Problems:

refractive error

opacities

Ages old

RETINAL STAGE

Translates optical image to neural impulses

Problems:

retinal disease

Since ophthalmoscope

NEURAL STAGE

Processes neural signals from inner retina to visual cortex to higher centers to allow visual functioning

Often overlooked

Presenter’s Notes

In visual functioning, we can very broadly define three stages, with very different properties: the optical, the retinal and the neural stage. In the optical stage, an image of the outside world is projected onto the retina. In the retina this optical image is translated into neural impulses. The neural stage processes these signals, beginning in the inner retina and proceeding to the visual cortex and higher centers to finally allow visual functioning.

The optical stage has been known for many centuries. Retinal diseases have been known since the invention of the ophthalmoscope, a century and a half ago.

Neural processing has often been overlooked and is gaining more attention only in the last decades.

(Slide 20)

Neural processing

Transcriber’s Note – Most of the text below in the Presenter’s Notes is displayed on the screen in chunks as the presenter speaks about each point. The text appears at various locations on the screen illustrating the presenter’s point.

Presenter’s Notes

How do we get from the retinal image to visually guided action? A significant intermediate step that is often insufficiently studied is that of the MENTAL MODEL of the environment. The initial transition from retinal image to mental model is largely subconscious and involuntary. The transition from mental model to visually guided action involves perception and cognition and conscious decision making.

We know that this intermediary step exists,

because we cannot interact directly with a retinal image that changes with every eye movement,

we need a stable model of the environment to plan our actions and to execute our locomotion through and our manipulation of that environment.

(Slide 21)

Slide Graphic

Diagram of the left side of the brain showing different colored boxes representing various areas of the brain. There are numerous arrows drawn to demonstrate the inter-relationship between all the different areas of the brain in visually-related activities.

Presenter’s Notes

Modern imaging techniques have given us a better idea of where various brain areas involved with these processes are located. I will not discuss those details.

I just want to point out that it speaks to the incredible plasticity of the brain that, while the neural processing undoubtedly is the most complex part of vision, it also is the part that most rarely presents problems, except in the cases that we are discussing today.

(Slide 22)

Seamless Involuntary Integration

Slide Description

A table containing two columns labeled, SENSORY INPUTS and CONFLICTS with four items in each column. The information from each column is listed below and separated by a comma.

SENSORY INPUTS, CONFLICTS

Visual Vestibular, Motion sickness

Left eye Right eye, Diplopia

Left hemisphere - Right hemisphere, Edge not detectable except in hemianopia

Ventral stream (what?) - Dorsal stream (where?), Deficits only in brain damage (CVI, TBI, CVA)

Presenter’s Notes

The previous slide depicted the many brain areas that are involved in different components of functional vision. Yet, the processing from all those areas is seamlessly integrated. We would never know that all this integration occurs, if it were not for cases where it fails.

Vestibular and visual cues are normally integrated. But if they contradict each other, we experience motion sickness.

The images from the right and the left eye are integrated into a single perception. If that fails, we experience diplopia.

Information from the left and the right hemisphere is integrated. However, we cannot detect any boundary, except in cases of hemianopia.

Information from the ventral stream (the “what” stream) and the dorsal stream (the “where” stream) is similarly integrated. But we notice problems only in cases of brain damage.

(Slide 23)

Retinal Image vs. Mental Model

Slide Description

A table with two columns and three items in each column.

RETINAL IMAGE, MENTAL MODEL

Changes constantly, Stable

Eye-centered, Environment-centerd

Presenter’s Notes

Let us look a little closer at the differences between the retinal image and the mental model.

We already mentioned that the retinal image is constantly changing, but that the mental model is stable. Also, the retinal image is eye-centered, whereas the mental model is environment-centered.

(Slide 24 & 25)

Slide Graphic

Photograph of an eye care specialist examining a woman in his office. Only a small portion of the scene is visible at any one time as if looking through the cardboard tube of a paper towel roll. The image is placed in motion by the presenter and moves around the photograph revealing different aspects of the photograph. The presenter’s notes below explain the purpose of this image.

Presenter’s Notes

We can simulate what a video camera sees when it scans the room. That shifting image looks unnatural and may make you feel sea sick. When we simulate the same with roving eye movements across a stable environment, the image looks far more natural.

(Slide 26)

Retinal Image vs. Mental Model

Slide Description

This slide shows the same table as in Slide 23 with the addition of one more item in each column.

RETINAL IMAGE, MENTAL MODEL

Changes constantly, Stable

Eye-centered, Environment-centerd

2-dimensional images, 3-dimensional objects

Presenter’s Notes

Another important difference is that the retinal image is made up of 2-dimensional figures, whereas our mental model is filled with 3-dimensional objects.

(Slide 27)

One 2-dimensional retinal image

Three distinct domains in the 3-dimensional Mental Model

Slide Graphic described in Presenter’s Notes

In this image from Escher, we see a pond with the reflection of some trees above, we see leaves floating on the surface and we see a fish swimming under the surface. On the retina, these three components are intermixed, but in our mental model they represent three distinct domains.

(Slide 28)

Retinal Image vs. Mental Model

Slide Description

Same table as in Slide 26.

Presenter’s Notes

Different activities have different visual demands.

In reading the emphasis is on recognition of finely detailed, 2-dimensional letter and word shapes. The question of WHAT we see is relatively more important than WHERE we see it. In mobility, on the other hand, we want to avoid obstacles. To determine WHERE a 3-dimensional obstacle is, is relatively more important than determining WHAT it is. In the manipulation of objects, the 2-dimensional detail and the 3-dimensional shape and location are both important.

(Slide 29)

Retinal Image vs. Mental Model

Slide Description

Same table as in Slide 28 with a new item in each column.

RETINAL IMAGE, MENTAL MODEL

Changes constantly, Stable

Eye-centered, Environment-centered

2-dimensional images, 3-dimensional objects

Strictly visual, Multi sensory - the blind have a mental model of their environment

Presenter’s Notes

The retinal image is strictly visual. However, the mental model is multi-sensory. Even the blind have a mental model of their environment, built entirely from non-visual information.

(Slide 30)

Retinal Image vs. Mental Model

Slide Description

Same table as in Slide 29 with a new item in each column.

RETINAL IMAGE, MENTAL MODEL

Changes constantly, Stable

Eye-centered, Environment-centered

2-dimensional images, 3-dimensional objects

Strictly visual, Multi sensory

Attention shifts drive visual search, Attention shifts occur in the mental model

Presenter’s Notes

When we shift our attention, we do that in the mental model. Those attention shifts then drive our eye movements and visual search.

(Slide 31)

One 2-dimensional retinal image

Three distinct domains in the 3-dimensional Mental Model

Attention shifts can occur between the domains of the Mental Model

Slide Graphic described in Presenter’s Notes

Looking at Escher’s picture again, we can shift our attention from the trees to the leaves, or to the fish, because they represent different domains in the mental model. We could never do that in the retinal image, where the three are completely interwoven.

(Slide 32)

Retinal Image vs. Mental Model

Slide Description

Same table as in Slide 30 with a new item in each column.

RETINAL IMAGE, MENTAL MODEL

Changes constantly, Stable

Eye-centered, Environment-centered

2-dimensional images, 3-dimensional objects

Strictly visual, Multi sensory

Attention shifts drive visual search, Attention shifts occur in the mental model

Ends at field limits - scotomata cause gaps, Extends around us - no gaps - accumulates in memory

Presenter’s Notes

Finally, the retinal image ends at the limits of our visual field and has gaps where the retina has blind spots. The mental model extends around us, although the area behind our backs has vague details, because we have gathered less information about that area. The retinal image changes from moment to moment. The mental model is persistent and filled with the best available information, accumulated in memory.

(Slide 33)

Central Scotoma

Slide Graphic

Same photograph of woman being examined by eye care specialist in office. This photo has a grayed out oval in the middle of the image representing what someone with a central scotoma would see.

Presenter’s Notes

The vision of people with a central scotoma is often simulated with a picture as shown here. In reality, people never see their central scotoma as a hole in their vision. The stationary picture is unnatural because it eliminates eye movements. When we introduce eye movements, we see that the scotoma disappears from our awareness, as long as it is moving. As soon as it stops, we see it again as one big gaping hole.

(Slide 34)

Steps in the Visual Process

Image formation

optical process, refractive error, opacities

Image detection

retinal process, topographic variations, visual field

Image processing

pre-processing in retina, analysis in visual cortex, synthesis (right arrow) visual perception (mental model)

Interpretation (in higher brain centers)

visual perception (right arrow) cognitive understanding, involves memory, recognition, other senses

Interaction with the multi-sensory mental model,

involves motor response

Presenter’s Notes

Having discussed the various stages, we can now summarize the steps in the visual process. The first step is image formation. It is an optical process. Its clarity is judged mainly by the fovea.

The next step is image detection in the outer retina. It introduces possible topographic variations due to the distribution of retinal disease. This introduces the importance of the visual field.

The next steps, starting in the inner retina, involve image processing. After analysis of the components in various brain centers and the synthesis of the result, it provides us with a visual perception, the mental model of our environment.

Next is interpretation of that mental modal and cognitive understanding. It involves memory, recognition and integration with other senses.

Finally, we are ready for a motor response to interact with the mental model of our environment.

(Slide 35)

The Visual Process

Slide Description

This slide contains a table with four boxes on the left side of the screen with the following text.

Box 1

Image formation

Image detection

Box 2

Image processing

analysis (right arrow) basic elements

Box 3

synthesis (right arrow) visual perception (right arrow) cognitive interpretation

Box 4

Interaction,

motor response

Presenter’s Notes

We can now summarize the steps in the visual process in these four boxes.

Image formation and image detection.

Basic image processing.

Synthesis to a visual perception and its cognitive interpretation, and finally,

Interaction and motor response.

(Slide 36)

The Visual Process

Slide Description

This slide, and the next 4 slides (36-40) use the same basic table as in Slide 35, with an additional table on the right side. In this slide the table on the right contains two columns titled Anatomy and Function. Each column has two boxes underneath.

Anatomy

Ocular

Cerebral

Function

Lower neural processes

Higher functions

These four boxes do not line up exactly. The boxes in the Function column are to the right of the boxes in the Anatomy column but the box for Lower neural processes aligns partly with the bottom half of the Ocular box and the top half of the Cerebral box. The Higher function aligns with the lower half of the Function box.

Presenter’s Notes

At this point it is important to note that our functional and anatomical divisions do not coincide. This is because the eye is not just a peripheral organ, in its development the retina is part of the brain.

(Slide 37)

The Visual Process

Slide Description

Same table as Slide 36 with additional box on right side labeled Visual Impairment. This box is aligned to the right of Box 1&2 from the other table that contain the text

Image formation, Image detection

Image processing, analysis (right arrow) basic elements

Presenter’s Notes

We are now ready to talk about terminology.

We can apply the term visual impairment to the top two boxes.

(Slide 38)

The Visual Process

Slide Description

Same table as in Slide 37 with an additional box on in the right side column labeled Visual Dysfunction. This box is aligned to the right of Box 3 from the other table that contains the text

synthesis (right arrow) visual perception (right arrow) cognitive interpretation

Presenter’s Notes

And the term visual dysfunction to the next, rather complex, group of steps that lead to cognitive interpretation.

(Slide 39)

The Visual Process

Slide Description

Same table as Slide 35 containing the 4 boxes. This slide has an additional table on the right side containing two columns that are not labeled. The first column has two boxes labeled Ocular, Cerebral. The second column has a box labeled Visual Impairment. The box labeled Visual Impairment aligns with the Ocular and Cerebral boxes and these align with Boxes 1&2 in the table on the left side. A third box is present in the table on the right and is labeled Cognitive – Visual Dysfunction. This box is aligned with Box 3 of the table on the left side that contains synthesis (right arrow) visual perception (right arrow) cognitive interpretation

Presenter’s Notes

Adding adjectives, we can divide the impairment box into Ocular Visual Impairment (OVI) and Cerebral Visual Impairment (CVI), to make an anatomical division.

At the visual dysfunction level we could speak of cerebral visual dysfunction. However, this would be a pleonasm, since all higher functions are cerebral. I prefer to use the term Cognitive Visual Dysfunction (CVD) to emphasize that dysfunctions are qualitatively different from impairments.

Using a separate term also solves the dilemma with some professionals who do not want to use the term CVI unless there is visual acuity or visual field loss. We can now say that disorders such as prosopagnosia or simultanagnosia are visual dysfunctions, rather than simple visual impairments.

(Slide 40)

The Visual Process

Slide Description

Same table as Slide 39 with one additional box at the bottom of the table on the right side labeled Motor Dysfunction. This box is aligned with Box 4 from the table on the left side that is labeled Interaction, motor response.

Presenter’s Notes

Adding the interaction with the environment, we add the possibility of motor dysfunctions.

(Slide 41)

Examples

Slide Description

This slide shows some examples for each of the categories.

Presenter’s Notes

Ocular Visual Impairments (OVI) include cases of optical scatter (cataracts) or defocus (refractive error) and of retinal scars and dystrophies.

Cerebral Visual Impairments (CVI) include sensory functions, such as visual acuity (amblyopia), field (hemianopia) and motion perception and oculo-motor functions such as fix and follow. So far, these functions are entirely visual.

Moving to visual dysfunction, other senses come into play as well. Examples include: visual neglect, hand-eye coordination (foot-eye coordination in mobility), figure-ground separation, color naming, etc.

In the motor dysfunction box we can mention that children in these groups often exhibit inconsistent behavior and are easily tired.

(Slide 42)

Role of Visual Acuity (and optical aids)

Presenter’s Notes

Looking again at visual acuity, we see that it can play a role at all levels.

At the optical level it plays a major role, but as we proceed the role of visual acuity lessens.

Field defects outside the fovea, even a hemianopia, do not affect acuity.

Acuity describes the magnification requirement, which is irrelevant for cognitive problems.

Normal cognition can coexist with total blindness; abnormal cognition can also coexist with normal visual acuity.

At the motor level, eccentric viewing may disrupt hand-eye coordination and acuity, but the acuity loss does not cause the eccentric viewing.

(Slide 43)

Interactions

Slide Description

This slide contains the diagram shown earlier with the two headings THE ORGAN & THE PERSON. The Organ has the subheadings Cause, Structure, Function. Sub-topics under these include Visual Functioning (how the EYE functions) and the Deficits under this, Visual Impairment.

The other side of the diagram, THE PERSON, has two subheadings; Abilities, Consequences. The sub-topics under these are Functional Vision (how the PERSON functions) and the Deficits under this, Visual Dysfunction.

Under this the presenter speaks about 4 points individually.

Defects at several levels (OVI, CVI, CVD) may coexist

Interactions may go both ways

Occlusion

Deprivation amblyopia

Suppression amblyopia

avoid diplopia

These are additional reasons to reject the automatic association of the word impairment with visual acuity deficits.

Some quick notes about interactions.

OVI, CVI and CVD may well coexist. They may also interact.

That interaction can go both ways. For example: Deprivation amblyopia is caused by lack of input. Suppression amblyopia is caused by negative feedback from a higher level.

Early visual impairments may limit a child’s general development if not properly addressed by the Blind Babies Foundation or other groups.

In cases where visual dysfunction and general dysfunction coexist, we may say that Cognitive Visual Dysfunction exists if the visual developmental age is less than the general developmental age. That statement, of course, assumes that we have adequate scales for both.

(Slide 44)

In Summary

Slide Description

This slide displays two tables. The first table to appear on the left is labeled Functional Categories and contains the boxes presented earlier that have Ocular & Cerebral aligned with Visual Impairment; Cognitive aligned with Visual Dysfunction; and Motor Dysfunction underneath.

The second table appears on the right suggests that you also consider, and is labeled Ability Ranges. The left column of this table contains two items. The first item, Normal (or adequate) performance is aligned with three boxes in the right column labeled; with reserve, lost reserve, with effort/aids. The second item in the left column, Restricted performance is aligned with three boxes in the right column labeled; restricted, marginal, impossible.

Underneath all of this are two points that will be displayed independently.

To be coordinated with anatomical insights

To be referenced to rehabilitative needs

Presenter’s Notes

In summary, we have provided you with functional categories to describe visual functioning. Those categories must be combined with ability ranges to describe whether the deficit is mild, moderate, severe or profound. Our time does not allow us to go into detail in this area. Additionally, these categories need to be coordinated with our developing anatomical insights, and also with the rehabilitative needs of the children or adults involved.

(Slide 45)

Proposed terms

Slide Description

This slide contains the same basic diagram in Slide 43 with the two major headings; THE ORGAN & THE PERSON. Under The Organ there are 3 subheadings; Cause, Structure, Function. Underneath this is the topic Visual Functions (how the VISUAL SYSTEM functions). Underneath this is Deficits: Visual Impairments. There are two items under Visual Impairments.

Ocular Visual Impairment

Cerebral Visual Impairment

(may or may not include VA loss)

The other side of the diagram, THE PERSON, contains two subheadings; Abilities, Consequences. The topic under these is Functional Vision (how the PERSON functions). Underneath this is the Deficit: Visual Dysfunction. There is one item under Visual Dysfunction; Cortical Visual Dysfunction

Presenter’s Notes

This slide summarizes the terms I propose to use.

We distinguish between visual functions, which describe how the eye and the visual system function and functional vision, which describes how the person functions.

When visual functions are disturbed, we speak of visual impairment. When functional vision is disturbed, we speak of visual dysfunction.

On the impairment side we distinguish between ocular and cerebral impairments.

On the dysfunction side, we speak of cognitive visual dysfunctions to emphasize the differences.

(Slide 46)

What next?

Researchers need to know

Which impairments and dysfunctions can be lumped, which to separate.

Educators need to know

How to distinguish visual dysfunctions from visual impairments and how to address both.

Third Parties (insurance) need

Simple guidelines for coverage, services

Presenter’s Notes

What should be next on our agenda? Creating better definitions will be helpful for many groups.

Researchers need to know not to lump dissimilar impairments and dysfunctions into one group.

Educators, who have predominantly learned how to deal wit visual impairments, need guidance to distinguish visual dysfunctions as a separate group that needs a very different approach.

Finally, the guidelines need to be simple enough to be understood by administrators, insurance and other third parties to prevent inappropriate denial of services.

(Slide 47 – final slide)

Thank you for your attention.

gus@

Colenbrander

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download