Vision and dyslexia

Prof Bruce EvansBSc (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

in relaxed

state as in

distance vision

crystalline lens

in accommodated

state as in

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 =

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

Meares-Irlen Syndrome / Visual Stress (MISViS)

The Intuitive Colorimeter

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

0.60.50.40.30.20.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

v'

u'

•hue, saturation, luminance varied independently

•eyes remain colour-adapted

•no coloured surfaces visible

•large gamut

•colour change continuous

hue

saturation

Precision Tinted Lenses (PTL)

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

Rose

Rose

Yellow

Blue

Turquoise

Green Orange

Purple

400 700wavelength (nm)

transmission (%)

100

0

7 dyes: 25 levels of deposition

Rose

Yellow

Orange

Green

Turquoise

BluePurple

Intuitive Overlays

Wilkins (1993) Figures courtesy of Prof. Arnold Wilkins

Aqua

Bl ue

Mint

Li me Or ange

Rose

Purpl e

wavelength (nm)400 700

100

0

refl

ecta

nce(%)

Pink

Yellow

GreyGrey

NOTE: OVERLAY COLOUR DIFFERS FROM LENS COLOUR

Assessing optometric interventions

Wilkins Rate of Reading Test

Wilkins et al. (1996) Ophthal. Physiol. Opt. 16, 491-497

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

Key research on Meares-Irlen Syndrome

PTL alleviate symptoms when reading

Wilkins, Evans, Busby et al. (1994)

Overlays improve speed of reading

Bouldoukian, Wilkins, Evans (2002)

PTL improve conventional measures

of reading Robinson & Foreman (2000)

The benefit from PTL is not explained

by ocular motor factorsEvans, Wilkins, Busby et al. (1995)

The benefit from PTL is linked to

pattern glare Evans, Wilkins, Brown et al. (1996)

.

N=6N=6

N=19N=19

N=11N=11

% when control glasses worn

% when active glasses worn.

N=6N=6

N=19N=19

N=11N=11

% when control glasses worn

% when active glasses worn

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 colourLightstone, 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)

86889092949698100102

Read

ing

rate

(w

pm

)

Chosen

overlay

Lenses

matching

colorimeter

No

overlay

or lens

Lenses matching

chosen overlay

86889092949698100102

Read

ing

rate

(w

pm

)

Chosen

overlay

Lenses

matching

colorimeter

No

overlay

or lens

Lenses matching

chosen overlay

SEQUENTIAL MANAGEMENT PLAN: educator with overlays

TEST WITH INTUITIVE OVERLAYSnegative

monitor

positive

IS THERE A SIGNIFICANT BENEFIT?

yesno

monitor

continued

ARE EYES HEALTHY?

yes

norefer

REFER TO OPTOMETRIST WITH COLORIMETER

continued

PRECISION TINTS

INTUITIVE COLORIMETRY

positive

negativemonitor

optometric

correctionIS THERE A SIGNIFICANT REFRACTIVE ERROR?

yes

no

IS THERE A SIGNIFICANT ORTHOPTIC ANOMALY?yes

no

optometric

correction/

treatment

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 / Wi lk ins I r len Chromagen

Screen ing Over lays o r PC Over lays None Tes t ing : ab i l i t y to f i nd op t ima l t i n t

Ve ry l a rge range o f co lours

Very la rge range o f co lou rs

9 co lours

Va l ida t ion W i lk ins Ra te o f Read ing Tes t

IDPS W i lk ins Ra te o f Read ing Tes t

Es tab l i shed 1993 1983 c . 1997 fo r dys lex ia

Des ign m in im ises metamer i sm

Yes Probab ly no t Probab ly no t

Ava i lab i l i t y o f con tac t l enses

Yes Yes Yes

Prac t i sed by eyecare p ro fess iona ls

Yes No Yes

Research Many papers , 1 D-M RCT

Many papers , 1 D-M RCT

Two papers , (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 textText 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

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

Society for Coloured lens Prescribers

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