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Vision and dyslexia

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					   Vision and dyslexia


                Prof Bruce Evans
BSc (Hons) PhD FCOptom DipCLP DipOrth FAAO FBCLA

Director of Research            Institute of Optometry
Visiting Professor                      City University
Private practice                    Brentwood, Essex
Which eyecare practitioner?

 Dispensing Opticians (5,100 in UK)
   Dispense spectacles
   Some also fit contact lenses

 Orthoptists (1,000 in UK)
   Mainly involved in orthoptics
   (binocular vision)
   Some also do vision screening
Which eyecare practitioner?

 Ophthalmologists
   In UK: 900 consultants; 1,400 in training

 Optometrists (10,400 in UK)
   Detect eye diseases
   Detect & treat refractive & orthoptic problems
   Prescribe glasses & contact lenses
The term dyslexia
 The word dyslexia means many
 different things to different people
 (Hartstein, 1968)

 a specific difficulty with reading and
 spelling

 “an unexpected problem in
 learning to read and spell in people
 who seem otherwise capable and
 intelligent”
What causes dyslexia?

 mainly a problem of making
 words into sounds (phonology)

 vision is a factor in some cases
Who diagnoses dyslexia?

 educational psychologist

 teachers may recognise signs

 optometrists & orthoptists only
 look at visual factors
Common visual
problems in dyslexia
 Meares-Irlen Syndrome

 poor binocular co-ordination

 focussing (accommodation)
 problems
Normal eye examination

 eye health

 refraction

 basic binocular co-ordination
Special investigation of
vision & learning
 12 extra tests of binocular
 coordination

 4 extra tests of focussing skills

 assessment of Meares-Irlen
 Syndrome
              PLAN
            INTRODUCTION

CONVENTIONAL OPTOMETRIC CORRELATES

   MAGNO (TRANSIENT) VISUAL DEFICIT

       BEHAVIORAL OPTOMETRY

MEARES-IRLEN SYNDROME& VISUAL STRESS

            CONCLUSIONS
Optometric correlates of reading difficulties:
binocular instability

SYMPTOMS:                blur, double vision, visual perceptual
                         distortions, eye strain & headaches

SIGNS:                   low fusional reserves,
                         unstable heterophoria




Evans et al. (1994) Ophthal. Physiol. Opt. 14 , 5-19.
Optometric correlates of reading difficulties:
binocular instability

SYMPTOMS:                blur, double vision, visual perceptual
                         distortions, eye strain & headaches

SIGNS:                   low fusional reserves,
                         unstable heterophoria

TREATMENT:               fusional reserve exercises
                         refractive correction




Evans et al. (1994) Ophthal. Physiol. Opt. 14 , 5-19.
Ocular accommodation


      crystalline lens    crystalline lens
         in relaxed      in accommodated
         state as in         state as in
      distance vision        near vision
Optometric correlates of dyslexia:
accommodative insufficiency

SYMPTOMS:    blur, eye strain & headaches

SIGNS:       low amplitude of accommodation,
             high accommodative lag

TREATMENT:   accommodative exercises (if appropriate)




                 Evans et al. (1994) Ophthal. Physiol. Opt. 14 , 5-19.
                PLAN

             INTRODUCTION

 CONVENTIONAL OPTOMETRIC CORRELATES

    MAGNO (TRANSIENT) VISUAL DEFICIT

THE DUNLOP TEST & BEHAVIORAL OPTOMETRY

MEARES-IRLEN SYNDROME& VISUAL STRESS

             CONCLUSIONS
Behavioral optometry
As many therapies as there
are practitioners
“no randomised controlled
trials”       (Jennings, 2000)


“a large majority of
behavioral management
therapies are not evidence-
based”          (Barrett, 2008)
                                     Voltaire: “Practical therapeutics is the art of
                                  keeping the patient entertained until nature effects
                                                        a cure”
“Tracking” & dyslexia
 Saccades are not unique to reading
 Most studies have not found a saccadic eye
 movement deficit in dyslexia
    Dyslexia influences saccades: “search for meaning”
    ADD influences saccades
 Treatments based on training saccadic or pursuit eye
 movements are controversial
 The DDAT has not been validated by masked
 controlled trials (PubMed search 15-Oct-06)
    “Reynolds et al. (2003) provides no evidence that
    DDAT is an effective form of treatment”      Snowling &
    Hulme (2003)

 PubMed search (15-Oct-06) reveals no published
 research on BrightStar system
               PLAN

            INTRODUCTION

CONVENTIONAL OPTOMETRIC CORRELATES

   MAGNO (TRANSIENT) VISUAL DEFICIT

MEARES-IRLEN SYNDROME & VISUAL STRESS

            CONCLUSIONS
Meares-Irlen Syndrome = symptoms + benefit from colour

  a.k.a. Scotopic Sensitivity syndrome, Irlen syndrome, visual stress

          Meares-Irlen Syndrome / Visual Stress (MISViS)
The Intuitive Colorimeter


     0.6



     0.5                                                                               hue
     0.4




v'   0.3



     0.2



     0.1



     0.0
           0.1   0.2   0.3   0.4   0.5   0.6



                       u'                                                             saturation

     •large gamut
     •colour change continuous

                                                 •hue, saturation, luminance varied independently
                                                 •eyes remain colour-adapted
                                                 •no coloured surfaces visible




                                               Wilkins et al. (1992)     Figures courtesy of Prof. Arnold Wilkins
 Precision Tinted Lenses (PTL)

                        Yellow


        Green
                                      Orange
                                                                                 Green              Yellow            Orange




    Turquoise                             Rose


                                                                              Rose
                                                                    Turquoise                                                  Rose
                             Purple
                Blue                                        100




                                                 transmission (%)
                                                                                         Blue                Purple
                                                                    0



                                                                        400                 700
                                                                          wavelength (nm)


                                                                                 7 dyes: 25 levels of deposition


Wilkins et al. (1992)                                                                       Figures courtesy of Prof. Arnold Wilkins
Intuitive Overlays



                                                          Li m e      Yellow      Or ange




                                                        Min t                        Rose




                                                        A qua                         Pink




                          reflectance (%)
                                            100




                                              0
                                                    Bl ue             Pu r pl e   Grey

                                                  400           700

                                             wavelength (nm)
  NOTE: OVERLAY COLOUR DIFFERS FROM LENS COLOUR
 Wilkins (1993)                                    Figures courtesy of Prof. Arnold Wilkins
Assessing optometric interventions
Wilkins Rate of Reading Test

     come see the play look up is cat not my and dog for you to
     the cat up dog and is play come you see for not to look my
     you for the and not see my play come is look dog cat to up
     dog to you and play cat up is my not come for the look see
     play come see cat not look dog is my up the for to and you
     to not cat for look is my and up come play you see the dog
     my play see to for you is the look up cat not dog come and
     look to for my come play the dog see you not cat up and is
     up come look for the not dog cat you to see is and my play
     is you dog for not cat my look come and up to play see the




                                Wilkins et al. (1996) Ophthal. Physiol. Opt. 16, 491-497
Key research on Meares-Irlen Syndrome




                                                              % when control glasses worn
                                                                                                   N=19
                                                                                                   N=19
 PTL alleviate symptoms when reading
                        Wilkins, Evans, Busby et al. (1994)

 Overlays improve speed of reading
                       Bouldoukian, Wilkins, Evans (2002)                                                        N=11
                                                                                                                 N=11


 PTL improve conventional measures                            N=6
                                                              N=6                           .
                                                                                                % when active glasses worn
 of reading         Robinson & Foreman (2000)

 The benefit from PTL is not explained
 by ocular motor factors
                        Evans, Wilkins, Busby et al. (1995)

 The benefit from PTL is linked to
 pattern glare    Evans, Wilkins, Brown et al. (1996)
                     Key research on Meares-Irlen Syndrome (cont)
                            >80% of people prescribed PTL are still using after one
                            year                             Evans, Patel, Wilkins et al. (1999)

                            Overlay colour cannot be used to predict lens colour
                                                                             Lightstone, Lightstone, Wilkins (1999)

                            Visual Stress is nearly as common in adults as children
                                                                                            Joseph & Evans (1999)

                            Visual Stress is about 2-3x more common in dyslexic
                            children than non-dyslexic               Kriss & Evans (2005)
Reading rate (wpm)




                     102
                     100
                      98
                      96
                      94
                      92
                      90
                      88
                      86
                           No                  Lenses
                           overlay   Chosen    matching    Lenses matching
                           or lens   overlay   colorimeter chosen overlay
SEQUENTIAL MANAGEMENT PLAN: educator with overlays


     TEST WITH INTUITIVE OVERLAYS                  monitor
                                       negative
                      positive


     IS THERE A SIGNIFICANT BENEFIT?               monitor
                                           no
                      yes



 REFER TO OPTOMETRIST WITH COLORIMETER




          ARE EYES HEALTHY?                refer
                                 no
                      yes


                 continued
                 continued




                                                      optometric
 IS THERE A SIGNIFICANT REFRACTIVE ERROR?             correction
                                              yes
                       no
                                                        optometric
IS THERE A SIGNIFICANT ORTHOPTIC ANOMALY?               correction/
                                               yes      treatment
                       no




         INTUITIVE COLORIMETRY              monitor
                                 negative
                      positive


             PRECISION TINTS




             YEARLY CHECKS
Which systems are validated by RCTs?

Validated
 Wilkins/MRC Intuitive Colorimeter
 Irlen
 ? Chromagen

Not validated
 Photosyntonics
 Orthoscopics & optopraxometer
 Tintavision
             Comparison of systems
                         MRC / Wilkins          Irlen                  Chromagen
Screening                Overlays or PC         Overlays               None
Testing: ability to      Very large             Very large             9 colours
find optimal tint        range of               range of
                         colours                colours
Validation               W ilkins Rate          IDPS                   W ilkins Rate
                         of Reading                                    of Reading
                         Test                                          Test
Established              1993                   1983                   c. 1997 for
                                                                       dyslexia
Design minimises         Yes                    Probably not           Probably not
metamerism
Availability of          Yes                    Yes                    Yes
contact lenses
Practised by eyecare     Yes                    No                     Yes
professionals
Research                 Ma n y p a p e r s ,   Ma n y p a p e r s ,   Two papers,
                         1 D-M RCT              1 D-M RCT              (1 ?D-M RCT)




Unproven techniques: Photosyntonics, Tintavision, Optopraxometer & Orthoscopics
Who needs referral to a visual stress clinic?

  Academic underachievement or difficulties with
  text (now or in the past)
  Visual perceptual distortions when viewing text
    Text moving, blurring, doubling, and seeing patterns on
    the page
  Headaches (including migraine) associated with
    Visual tasks (e.g., text)
    Flickering or fluorescent lighting
    School / HE establishment
    Offices
             Society for Coloured lens Prescribers



For prescribers of precision tinted lenses
who sign up to a code of conduct about:
  relevant CET - 10 hrs in last 5 yrs
  Equipment - for BV & PTL
  Evidence-based practice
List will be publicised to teachers,
educational psychologists, parents
www.s4clp.org
Conclusions
Certain visual problems are
particularly common in people
with reading difficulties
   Meares-Irlen Syndrome, binocular
   instability, accommodative
   insufficiency


All these problems can cause
similar symptoms
   Eyestrain, headaches, visual
   perceptual distortions


People with reading difficulties
or these symptoms should be
referred to interested eyecare
practitioners

				
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posted:3/25/2012
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