Assessment and Rehabilitation of Functional Vision

1. Assessment and Rehabilitation of Functional Vision Report for WOC-2008 – Hong Kong and Vision-2008 – Montreal August Colenbrander, MD - San FranciscoNo financial interest

2. 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

3. 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 www.ICOph.org/standards

4. Hong Kong, June 2008 Assessment and Rehabilitation of Functional Vision with Emphasis on RehabilitationOutcomes • Rehabilitation affects individual performance • Rehabilitation requires Documented Outcomes www.ICOph.org/standards

5. ASPECTS of VISION LOSS THREE OBJECTS ?

6. THREE OBJECTS ?

7. SAME OBJECT DIFFERENT ASPECTS

8. A S P E C T S Reveal properties of the object they also Reveal the point of viewof the beholder

9. 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?

10. Aspects of Visual Functioning Tissue Organ Person Society ScarAtrophyLoss AcuityFieldContrast ReadingMobilityADLs ParticipationQuality of Life

11. Aspects of Visual Functioning Tissue Organ Person Society ReadingMobilityFace recognition Job lossQuality of Life ScarAtrophyLoss AcuityFieldContrast VISUAL FUNCTIONShow the EYE functions FUNCTIONAL VISIONhow the PERSON functions

12. Aspects of Reading Tissue Organ Person Society MobilityFace recognitionReading ParticipationQuality of Life ScarAtrophyLoss AcuityFieldContrast Example:READING Print size, speed Reading endurance Reading enjoyment

13. Medical outcomes Medical Interventions Tertiary outcome, but ultimate goal: Improved Quality of Life Secondary outcome: Improved Visual Abilities Primary outcome: Improved Visual Functions Visual acuity is widely used Contrast should be considered for refractive surgeryScotoma topography determines reading ability

14. Rehabilitative outcomes Rehabilitative Interventions Ultimate Goal: Improved Quality of Life Primary outcome: Improved Visual Abilities Generic tools may be used NEI-VFQEuroQol Many others Outcome measurements must be specific and related to specific, preset goals Generic tools are not sensitive enough

15. Assessment of Visual Functions Tissue Organ Person Society VISUAL FUNCTIONShow the EYE functions Can be measured, one parameter at a time sizecontrastlighting → visibility vary constant constant → visual acuity constant vary constant → contrast sensitivity constant constant vary → dark adaptation Results in precise threshold measurements Parameters ofVisual Functionvisual acuityvisual fieldcontrast sensitivitycolor visiondark adaptation

16. Tests - One Parameter at a time Visual Acuity Threshold Contrast Sensitivity Threshold Dark adaptation Threshold

17. Assessment of Functional Vision Tissue Organ Person Society VISUAL FUNCTIONShow the EYE functions FUNCTIONAL VISIONhow the PERSON functions Actual tasks involve multiplevisual function parameters Actual tasks require sustainable performanceat a supra-threshold level Task performance can be assessed through self-report questionnaires or through time-based observation Visual skills and abilities Visual task performance ReadingOrientation, MobilityActivities of Daily Living, driving Visual communicationVisual job skills

18. Quality of Life Tissue Organ Person Societal context FUNCTIONAL VISIONhow the PERSON functions Quality of Life is a highlysubjective 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 Vision-related Quality of Life Making, keeping friendshipsSocial skillsSelf confidence, Fear of fallsCoping skillsOrganizing one’s lifeAsking for assistance

19. Main Aspects of Vision Organ Person Societal context Parameters of Visual Functions Task performance, Functional Vision Vision-related Quality of Life ReadingOrientation, MobilityActivities of Daily LivingVisual communicationVisual job skills Making, keeping friendshipsSocial skillsSelf confidence, Fear of fallsCoping skillsAsking for assistance Visual acuityVisual fieldContrast sensitivityColor visionDark adaptation We need to clearly distinguish these different aspects Amenable to precise threshold measurements Requires, supra-threshold, sustainable performance Subjective experience of Satisfaction is goal

20. Functional Vision Organ Person Societal context Parameters of Visual Functions Task performance, Functional Vision Vision-related Quality of Life Visual acuityVisual fieldContrast sensitivityColor visionDark adaptation ReadingOrientation, MobilityActivities of Daily LivingVisual communicationVisual job skills Making, keeping friendshipsSocial skillsSelf confidence, Fear of fallsCoping skillsAsking for assistance We need to clearly distinguish these different aspects Amenable to precise threshold measurements Requires, supra-threshold, sustainable performance Subjective experience of Satisfaction is goal

21. Aspects of Functional Vision Organ Person Societal context Functional Vision Resources Reading Goals Vision Touch Reading print Reading Braille Reading poetry Reading manuals Reading maps Enjoyment Information Orientation Different Resources Different Goals

22. Aspects of Functional Vision Organ Person Societal context Functional Vision Resources Abilities / Activities Tasks I C I D H(WHO, 1980) I C F(WHO, 2001) Medical Model of Disability used in Rehabilitation Disability as individual challengefor rehabilitation Social Model of Disability Disability rights Disability as social challenge for public policy

23. Aspects of Functional Vision Organ Person Societal context Functional Vision Resources Abilities / Activities Tasks Medical and Social model are not exclusive; they are complementary The Medical Model is important for rehabilitation and individual health care The Social Model is important for public healthand health care policy

24. Aspects of Functional Vision Organ Person Societal context Functional Vision RehabilitationResources Abilities / Activities Tasks I 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

25. Aspects of Functional Vision Organ Person Societal context Functional Vision RehabilitationResources Abilities / Activities Tasks I C F(WHO, 2001) Visual Non-visual Magnification Illumination Contrast Alternative skills Modified 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

26. Aspects of Functional Vision Organ Person Societal context Functional Vision Resources Abilities / Activities Tasks Need for a taxonomy ofTASKS and ACTIVITIES ICF can provide a frameworkActivity Inventoryfor more detail Need for a catalogue of RESOURCES For vision enhancementand for vision substitution ISO standard 9999 Need for SCALES to demonstrate the EFFECTIVENESS of Rehabilitation

27. Measurement Approaches VISUAL FUNCTIONS FUNCTIONAL VISIONhow the VISUAL SYSTEM functions how the PERSON functions Defects: VISUAL IMPAIRMENT VISUAL DYSFUNCTION Basic visual functions Tests use a variable stimulus to obtain a constant response (threshold, 50% correct)

28. Measuring Visual Functions Good ability Demanding task Subject 1 Change stimulus to find threshold Subject 2 Subject 3 Poor ability Easy task

29. Measuring Visual Functions Good ability Demanding task Subject 1 Change stimulus to find threshold Subject 2 Subject 3 Poor ability Easy task

30. Measuring Visual Functions Good ability Demanding task Subject 1 Measure threshold for a physical stimulus parameter Change stimulus to find threshold Subject 2 Subject 3 Poor ability Easy task

31. Real Life – Multiple Parameters Detail varies Contrast varies Illumination varies Need for SUSTAINABLE performance

32. Measurement Approaches VISUAL FUNCTIONS FUNCTIONAL VISIONhow the VISUAL SYSTEM functions how the PERSON functions Defects: VISUAL IMPAIRMENT VISUAL DYSFUNCTION Basic visual functions Complex visual functions Tests use a fixed task and record a variable response (sustainable performance must be > 50%) Tests use a variable stimulus to obtain a constant response (threshold = 50% correct)

33. Measuring Functional Vision Good ability Demanding task Task is easy Subject 1 Standardize the task, measure subject’s performance Task is possible Subject 2 Task is hard Subject 3 Poor ability Easy task

34. Measuring Functional Vision Good ability Demanding task Cataract surgery - post Multiple tasks are needed evenly spread over the difficulty scale. Different ranges are needed fordifferentconditions. before after AMD rehab - before Poor ability Easy task

35. Measuring Functional Vision Good ability Demanding task Cataract surgery - post easy Surgery has little effect very easy hard before Surgery is effective easy Poor ability Easy task

36. Measuring Functional Vision Good ability Demanding task hard Rehabilitation has little effect Rehabilitation is effective hard after easy AMD rehab - before hard Poor ability Easy task

37. Measuring Functional Vision Good ability Demanding task Cataract surgery - post Rasch analysis allows us to match the range of difficultiesto the range of abilities. before after AMD rehab - before Poor ability Easy task

38. 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

39. 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

40. 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

41. 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

42. Example LOVIT study – RESULTS goal = reading Outcome controls treated Effect size Stelmack et al – Arch. Ophth., May 2008

43. Thank you gus @ ski.org www.ski.org/Colenbrander