assessment and rehabilitation of functional vision report for woc-2008 – hong kong and vision-2008...

Assessment Assessment andand

Rehabilitation Rehabilitation of of

Functional VisionFunctional Vision

Report for WOC-2008 – Hong Kong and Vision-2008 – Montreal

August Colenbrander, MD - San FranciscoNo financial interest

Sydney, April 2002

Aspects and Ranges of Vision

Loss with Emphasis on Population Surveys

Vision loss is a continuum

Population surveys hide individual differences

www.ICOph.org/standards

THE ORGAN THE PERSON

Structural change, at

the organ level Functional change at

the Organ level Skills, Abilities (ADL)

of the individual Social, Economic Consequences

Eye Health Visual Functions Functional Vision Quality of Life

Range of Normal Vision

(Nea

r-)N

orm

al V

isio

n

Mild Vision Loss

Moderate Vision Loss

Severe Vision Loss

L

ow

Vis

ion

Profound Vision Loss

Near- Blindness

(Nea

r-)

Bli

nd

nes

s

Blindness

VISUAL

STANDARDS

ASPECTS and RANGES

of VISION LOSS

with Emphasis on Population Surveys

Report prepared for the International Council of Ophthalmology at the 29th International Congress of Ophthalmology Sydney, Australia, April 2002

Sao Paulo, February 2006

Vision Requirements for

Driving Safety with Emphasis on

Individual Assessment

Driving requires more than visual acuity alone

Licensing should allow for individual differences



Structural change at the organ level

Functional change at the Organ level

Skills, Abilities (ADL) of the individual

Social, Economic Consequences



(Nea

r-)N

orm

al V

isio

n

Mild Vision Loss


Severe Vision Loss

L

ow

Vis

ion


Near- Blindness

(Nea

r-)

Bli

nd

nes

s

Blindness

VISUAL STANDARDS

VISION

REQUIREMENTS

for DRIVING SAFETY

with Emphasis on Individual Assessment

Report prepared for the International Council of Ophthalmology at the 30th World Ophthalmology Congress Sao Paulo, Brazil, February 2006

Hong Kong, June 2008

Assessment and Rehabilitation of

Functional Vision with Emphasis on

Rehabilitation Outcomes

Rehabilitation affects individual performance

Rehabilitation requires Documented Outcomes



Structural change at the organ level

Functional change at the Organ level

Skills, Abilities (ADL) of the individual

Social, Economic Consequences



(Nea

r-)N

orm

al V

isio

n

Mild Vision Loss


Severe Vision Loss

L

ow

Vis

ion


Near- Blindness

(Nea

r-)

Bli

nd

nes

s

Blindness

VISUAL STANDARDS

ASSESSMENT and

REHABILITATION of

FUNCTIONAL VISION

Report prepared for presentation at the World Ophthalmology Congress – Hong Kong, 2008 of the International Council of Ophthalmology and the Vision-2008 conference – Montreal, 2008 of the International Society for Low Vision Research and Rehabilitation

THREE OBJECTS ?

ASPECTS of VISION LOSS

THREE OBJECTS ?

SAME OBJECT

DIFFERENT ASPECTS

A S P E C T S

Reveal properties of the object

they also

Reveal the point of viewof the beholder

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?

Aspects of Visual Functioning THE ORGAN THE PERSON

Cause Structure Function Abilities Consequences

Tissue Organ Person SocietyScarAtrophyLoss

AcuityFieldContrast

ReadingMobilityADLs

ParticipationQuality of Life



ScarAtrophyLoss

AcuityFieldContrast

ReadingMobilityFace recognition

Job lossQuality of Life

VISUAL FUNCTIONS how the EYE functions

FUNCTIONAL VISION how the PERSON functions

Tissue Organ Person Society

Aspects of Visual Functioning



ScarAtrophyLoss

AcuityFieldContrast

MobilityFace recognitionReading

ParticipationQuality of Life


Aspects of Reading

Example:READING

Print size, speed

Reading endurance

Reading enjoyment

Medical outcomesTHE ORGAN THE PERSON

Structure Function Abilities Consequences Environment

Medical Interventions

Secondary outcome: Improved Visual Abilities

Tertiary outcome, but ultimate goal: Improved Quality of Life

Primary outcome: Improved Visual Functions

Visual acuity is widely used Contrast should be considered for refractive surgery Scotoma topography determines reading ability

Rehabilitative outcomesTHE ORGAN THE PERSON


Rehabilitative Interventions

Primary outcome: Improved Visual Abilities

Ultimate Goal: Improved Quality of Life

Outcome measurements must be specific and related to specific, preset goals

Generic tools are not sensitive enough

Generic tools may be used

NEI-VFQEuroQol

Many others

Assessment of Visual FunctionsTHE ORGAN THE PERSON




Parameters of Visual Functionvisual acuity

visual fieldcontrast sensitivity

color visiondark adaptation

Can be measured, one parameter at a time

size contrast lighting → visibilityvary constant constant → visual acuityconstant vary constant → contrast sensitivityconstant constant vary → dark adaptation

Results in precise threshold measurements

Tests - One Parameter at Tests - One Parameter at a timea time

Visual Acuity Threshold

Contrast Sensitivity Threshold

Dark adaptation Threshold

Assessment of Functional VisionTHE ORGAN THE PERSON


FUNCTIONAL VISIONhow the PERSON functions


Visual skills and abilities Visual task performance

ReadingOrientation, MobilityActivities of Daily Living, driving Visual communicationVisual job skills

Actual tasks involve multiple visual function parameters

Actual tasks require sustainable performance at a supra-threshold level

Task performance can be assessed through self-report questionnaires or through time-based observation


Quality of LifeTHE ORGAN THE PERSON


FUNCTIONAL VISION how the PERSON functions

Tissue Organ Person Societal context

Vision-related Quality of Life

Making, keeping friendshipsSocial skillsSelf confidence, Fear of fallsCoping skillsOrganizing one’s lifeAsking for assistance

Quality of Life is a highly subjective judgment

“Satisfaction” is individual goal

Time trade-off and related techniques balance quality of life against quantity of life

Many questionnaires mix items from all three domains

ReadingOrientation, MobilityActivities of Daily LivingVisual communicationVisual job skills



Task performance, Functional Vision

Organ Person Societal context

Making, keeping friendshipsSocial skillsSelf confidence, Fear of fallsCoping skillsAsking for assistance

Parameters of Visual Functions

Vision-related Quality of Life

Visual acuityVisual fieldContrast sensitivityColor visionDark adaptation

Amenable to precise threshold measurements

Requires, supra-threshold, sustainable performance

Subjective experience of Satisfaction is goal

We need to clearly distinguish these different aspects

Main Aspects of Vision

ReadingOrientation, MobilityActivities of Daily LivingVisual communicationVisual job skills



Task performance, Functional Vision


Making, keeping friendshipsSocial skillsSelf confidence, Fear of fallsCoping skillsAsking for assistance

Parameters of Visual Functions

Vision-related Quality of Life Visual acuity

Visual fieldContrast sensitivityColor visionDark adaptation

We need to clearly distinguish these different aspectsAmenable to precise threshold measurements

Requires, supra-threshold, sustainable performance

Subjective experience of Satisfaction is goal

Functional Vision



Functional Vision


Reading

Reading printReading Braille

Reading poetryReading manualsReading maps

Aspects of Functional Vision

Resources Goals

VisionTouch

Different Resources

EnjoymentInformationOrientation

Different Goals

Aspects of Functional VisionTHE ORGAN THE PERSON


Functional Vision


Abilities / ActivitiesResources Tasks

I C I D H (WHO, 1980)

Social Model of Disability Disability rights

Disability as social challenge for public policy

Medical Model of Disability used in Rehabilitation

Disability as individual challenge for rehabilitation

I C F (WHO, 2001)



Functional Vision


Abilities / ActivitiesResources Tasks

Medical and Social model are not exclusive; they are complementary

The Medical Model is important for rehabilitationand individual health care

The Social Model is important for public health and health care policy




Functional Vision


Abilities / ActivitiesRehabilitation

Resources TasksI C F (WHO, 2001)Visual

Non-visual

Instrumental

Reading print

Reading Braille

Talking books

Example: d16.. Applying Knowledge d160 Focusing attention d163 Thinking d166 Reading (text or Braille) d170 Writing d172 Calculating d175 Problem solving




Functional Vision


Abilities / ActivitiesRehabilitation

Resources TasksI C F (WHO, 2001)Visual

Non-visual

MagnificationIlluminationContrast

Alternative skillsModified tasks

Example: e1... Products, Technology e115 for daily living e120 for mobility, transportation e125 for communication e130 for education e135 for employment e140 for culture, recreation




Functional Vision


Abilities / Activities

Need for a taxonomy ofTASKS and ACTIVITIES

ICF can provide a framework

Activity Inventory for more detail


Resources

Need for a catalogue of RESOURCES

For vision enhancementand for vision substitution

ISO standard 9999

Need for SCALES to demonstrate the EFFECTIVENESS of Rehabilitation

Tasks



VISUAL FUNCTIONS FUNCTIONAL VISION how the VISUAL SYSTEM functions how the PERSON functions

Defects: VISUAL IMPAIRMENT VISUAL DYSFUNCTION

Tests use a variable stimulus to obtain a constant response

(threshold, 50% correct)

Basic visual functions

Measurement Approaches

Measuring Visual Functions

Poor ability Easy task

Good ability Demanding task

Subject 1

Subject 2

Subject 3

Change stimulus to find threshold

Measuring Visual Functions



Subject 1

Subject 2

Subject 3

Measure threshold for a physical stimulus parameter

Change stimulus to find threshold

Real Life – Multiple Real Life – Multiple ParametersParameters

Need for SUSTAINABLE performanceDetail varies Contrast varies Illumination varies



VISUAL FUNCTIONS FUNCTIONAL VISION how the VISUAL SYSTEM functions how the PERSON functions

Defects: VISUAL IMPAIRMENT VISUAL DYSFUNCTION

Tests use a variable stimulus to obtain a constant response

(threshold = 50% correct)

Tests use a fixed task and record a variable response

(sustainable performance must be > 50%)

Measurement Approaches

Basic visual functions Complex visual functions

Measuring Functional VisionGood ability Demanding task


Task is easy

Standardize the task,

measure subject’s performance

Task is possible

Task is hard

Subject 1

Subject 2

Subject 3

Measuring Functional Vision


Cataract surgery - postMultiple tasks

are needed

evenly

spread over

the difficulty

scale.

before

after

AMD rehab - before

Different ranges are needed fordifferentconditions.




Cataract surgery - post

before


easy

very easyhard

easy

Surgery has little effect

Surgery is effective



after

AMD rehab - before


hard

hard

hard

easy

Rehabilitation is effective

Rehabilitation has little effect



Cataract surgery - post

before

after

AMD rehab - before


Rasch analysis

allows us

to match the

range

of difficulties

to the range

of abilities.

Where are we ?

OUTCOME studies Interventions are often poorly defined

This makes replication difficult

Pre- and post- interviews by the clinician may bias results

Questions unrelated to the rehabilitation objectives may dilute the results

Questionnaires for cataract and refractive surgery abound, but may not fit the problems of diabetic retinopathy,

of AMD or of severe cataract in underserved areas

Where are we ?

Need for different level questionnaires Very simple questions (one or two) for use in a general eye care setting, to determine the need for rehabilitation

Intake questions for use in a rehabilitation setting, to determine rehabilitation priorities and to set up a rehabilitation plan with defined objectives

Outcome questions to determine whether the objectives have been met

Examples

Rasch analysis Strongly promoted by Massof Used to validatie an Activity Inventory on

over 1,800 Low Vision patients at Johns Hopkins

Rasch analysis is mathematically complicated, but it significantly increases the power of questionnaires,

many of which had poor psychometric qualities

Applied for the ability range of cataract and refractive surgery by Pesudovs

Example

LOVIT study (Veterans Affairs, USA) The first randomized control study of Vision Rehabilitation,

comparing treatment to 4-month waiting

Masked interviewers conducted telephone interviews, using Rasch validated questionnaires (48 reading

related questions) at intake and after 4 months

Patients received a well-defined intervention protocol (5 weeks) aimed primarily at visual reading

126 patients with macular disease, 5x2 hours in clinic, 17 hours homework, 1 home visit

Example

LOVIT study – RESULTS

Visual reading

-0.37 +2.40

Vision overall

-0.20 +1.67

Visual motor skills

-0.04 +1.71

Information processing

-0.20 +1.38

Mobility -0.27 +0.66

Outcome Outcome controlscontrols treated Effect treated Effect sizesize

Stelmack et al – Arch. Ophth., May 2008Stelmack et al – Arch. Ophth., May 2008

goal = reading

Thank you

gus @ ski.org

www.ski.org/Colenbrander

assessment and rehabilitation of functional vision report for woc-2008 – hong kong and vision-2008...

Documents

aspects of vision loss

beholder slide

reading ability slide

abilities visual tas

ranges of vision loss

vision requirements

population surveys vision

individual assessment