optometric educators ltd driven to distraction bioptic driving conference 21 st june 2004 nick...

Optometric Educators LtdOptometric Educators Ltd

Driven to Driven to DistractionDistraction

Bioptic Driving Bioptic Driving ConferenceConference

2121stst June 2004 June 2004

Nick Rumney Nick Rumney MScOptom FCOptom FAAOMScOptom FCOptom FAAO

Acknowledgements: Mark Dunne, Algis Acknowledgements: Mark Dunne, Algis VingrysVingrys


Aim of presentationAim of presentation

• Update present vision and driving Update present vision and driving regulationsregulationsSome recent researchSome recent research

• Discuss experiences as DVLA fields Discuss experiences as DVLA fields centrecentre

• Driving and colour visionDriving and colour vision

• Driving and low visionDriving and low vision


Any standard should be assessed for:Any standard should be assessed for:

• Criterion validityCriterion validity relationship between test and driving safetyrelationship between test and driving safety

• Prevalence of impairmentsPrevalence of impairments relates to number of drivers that will be excluded based upon test resultsrelates to number of drivers that will be excluded based upon test results if high then problems with public/political acceptanceif high then problems with public/political acceptance if low then little impact on driving safetyif low then little impact on driving safety

• ReproducibilityReproducibility• Face validityFace validity

acceptability as a relevant measure of driving capacityacceptability as a relevant measure of driving capacity

• Construct validityConstruct validity ability to measure the designated visual functionability to measure the designated visual function

• ApplicabilityApplicability for large scale screeningfor large scale screening

• Resistance to fraudResistance to fraud• tests that improve with subject training not advisabletests that improve with subject training not advisable

van Rijn & Völker-Dieben van Rijn & Völker-Dieben (1999)(1999)


Evidence based researchEvidence based research

• Static VA vs crash ratesStatic VA vs crash rates Weak correlationWeak correlation (Hills & Burg 1977, Ivers et al 1999)(Hills & Burg 1977, Ivers et al 1999)

No sig > in collision rates using 6/12 cut-offNo sig > in collision rates using 6/12 cut-off (Burg (Burg

1971, Hills & Burg 1977, Owlsey et al 1998)1971, Hills & Burg 1977, Owlsey et al 1998)

• Visual Field vs crash ratesVisual Field vs crash rates No significant relationship No significant relationship (Burg 1971, Hills & Burg 1977, Ivers et al (Burg 1971, Hills & Burg 1977, Ivers et al

1999, Council & Allen, 1974, Owlsey et al 1998, )1999, Council & Allen, 1974, Owlsey et al 1998, )

but… unsophisticated methods of assessment, poorly but… unsophisticated methods of assessment, poorly controlled testing conditions, failure to adjust for controlled testing conditions, failure to adjust for mileage ratemileage rate

More recent data More recent data (Johnson & Keltner, 1983)(Johnson & Keltner, 1983)

• Modern techniques, 10,000 drivers => severe binocular Modern techniques, 10,000 drivers => severe binocular field loss is associated with 100% rise in crash ratesfield loss is associated with 100% rise in crash rates


VA StandardVA Standard• To read in good light (with Rx) a car registration of To read in good light (with Rx) a car registration of

79.4mm high at 20.5 metres79.4mm high at 20.5 metres recent change to 19.5m (new plates)recent change to 19.5m (new plates) Geometric acuity of 13.4’ arc = 6/15 letterGeometric acuity of 13.4’ arc = 6/15 letter

• NO precise Snellen !NO precise Snellen ! 6/9-2 (actually 6/10) passes or fails same proportion of 6/9-2 (actually 6/10) passes or fails same proportion of

people (but not necc. same people) people (but not necc. same people) ** Probability of passing Probability of passing

• 96% for 6/7.596% for 6/7.5• 6% for 6/186% for 6/18

DVLA accept 6/12 from accredited assessment centresDVLA accept 6/12 from accredited assessment centres* * Drasdo & Haggerty (1981)Drasdo & Haggerty (1981)


• Two groups patientsTwo groups patients50 with 6/9 and 50 with 6/12 (BEO)50 with 6/9 and 50 with 6/12 (BEO)Numberplate chosen moderately Numberplate chosen moderately

difficultdifficult

Between 9am and 3pm good weatherBetween 9am and 3pm good weatherNo refraction or fields assessmentNo refraction or fields assessment

Reliability of SnellenReliability of Snellen

F758 EKY

Currie et al 2000


Reliability of SnellenReliability of Snellen

37

1317

33

0

5

10

15

20

25

30

35

40

'6/9 '6/12

Pass NP Fail NP

Currie et al 2000


QuestionnaireQuestionnaire

• 100 questionnaires to 100 questionnaires to GP (63%), Optom (60%), Ophthal (72%)GP (63%), Optom (60%), Ophthal (72%)

““When clients ask you whether or not they may drive (no When clients ask you whether or not they may drive (no dip or field loss) at what level of acuity do you tell them dip or field loss) at what level of acuity do you tell them they should not drive ? how would you measure it ?”they should not drive ? how would you measure it ?”

• 25% GP’s unsure and 94% of these advised see optom25% GP’s unsure and 94% of these advised see optom• 22% of optometrists advised borderline to self assess22% of optometrists advised borderline to self assess• 13% of ophthal advised self assessment (4 quoted wrong 13% of ophthal advised self assessment (4 quoted wrong

distance !)distance !)

Currie et al 2000


Professional opinionProfessional opinion

Acuity cut-off

0

10

20

30

40

50

60

70

80

'6/9 '6/10 '6/12 <6/12 '6/15 '6/18 <6/18 NPT

GP Optometrist Ophthalmologist

Currie et al 2000


ConclusionConclusion

• Drivers receive a spectrum of adviceDrivers receive a spectrum of advice

• Advice is either upper limit (caution) Advice is either upper limit (caution) or lower limit (stop driving)or lower limit (stop driving)

• Neither is incorrect if accompanied Neither is incorrect if accompanied by advice on legal requirement.by advice on legal requirement.

• At 6/9 or less only true advice is At 6/9 or less only true advice is “I don't know you had better check it”“I don't know you had better check it”

Currie et al 2000


Visual FieldsVisual Fields

• NO statutory but if there is evidence a NO statutory but if there is evidence a defect exists then must passdefect exists then must pass120120o o (H) (H) 2020oo (above & below) (above & below)No defect in binocular field within central No defect in binocular field within central

2020oo

Effectively excludes all hemianopes, quadrantinopes and many diabetics Effectively excludes all hemianopes, quadrantinopes and many diabetics

with bilateral pan-retinal photocoagulationwith bilateral pan-retinal photocoagulation


Human binocular field extends 200° horizontally x 135° verticallyAnderson (1992)

RELE

XX

X denotes blind spot


European guidelinesEuropean guidelines(minimum standard)(minimum standard)

• Binocular visual field of at least 120Binocular visual field of at least 120° horizontally° horizontallyno specific guidelines on methodologyno specific guidelines on methodologyno mention of central visual fieldsno mention of central visual fields

22ndnd EC directive EC directiveCited by van Rijn & VCited by van Rijn & Vöölker-Dieben (1999)lker-Dieben (1999)


European GuidelinesHorizontal binocular field of 120°

RELE

XX


UK Guidelines UK Guidelines (minimum standard)(minimum standard)

• Esterman binocular fields – for consistencyEsterman binocular fields – for consistency Horizontal field of at least 120Horizontal field of at least 120°° No defect that encroaches within 20° of fixationNo defect that encroaches within 20° of fixation Acceptable deficitsAcceptable deficits

• Scattered single points missingScattered single points missing• Single cluster of 2 or 3 contiguous points Single cluster of 2 or 3 contiguous points

Unacceptable deficitsUnacceptable deficits• 4 or more contiguous points4 or more contiguous points• Single cluster up to 20Single cluster up to 20OO plus additional points within 20 plus additional points within 20OO

Longstanding defectsLongstanding defects• Present and static for > 5 years, case by case basisPresent and static for > 5 years, case by case basis

Recommended by the Royal College of Ophthalmologists & The Secretary of State’s (DETR) Honorary Visual Panel, in application Recommended by the Royal College of Ophthalmologists & The Secretary of State’s (DETR) Honorary Visual Panel, in application of the 2of the 2ndnd EC directive EC directive


UK GuidelinesEsterman binocular fields, horizontal field of 120°,

minimal losses within 20° of fixation

RELE

XX


Limitations of current guidelinesLimitations of current guidelines

• The relationship between the visual The relationship between the visual field and driving safety has not been field and driving safety has not been establishedestablished

• The most appropriate methods for The most appropriate methods for measuring the visual field has not measuring the visual field has not been establishedbeen established

• It has not been established whether It has not been established whether better tests are available e.g. UFOVbetter tests are available e.g. UFOV

van Rijn & Völker-Dieben van Rijn & Völker-Dieben (1999)(1999)


Driving fixation patternsApproximate 99% Approximate 99% horizontal limits horizontal limits ((°)°)

Approximate 99% Approximate 99% vertical limits (vertical limits (°)°)

RURALRURAL ± ± 2727°° ±± 15 15°°

SUBURBANSUBURBAN ±± 27 27°° ±± 15 15°°

DUAL DUAL CARRIAGEWAYCARRIAGEWAY ±± 37 37°° ±± 22 22°°

Dunne after: Crundall & Underwood (1998)


Driving fixation patternsdual carriageway rural/suburban

UFOV test

Esterman binocular field test

UK fieldstandard


VF StandardVF Standard

• DVLADVLAAccredited centres (Ophthalmologist, Accredited centres (Ophthalmologist,

Orthoptist and Optometrists)Orthoptist and Optometrists)• Fee paid £38.00Fee paid £38.00

Static perimeterStatic perimeterDicon, Henson, HumphreyDicon, Henson, HumphreyEsterman binocular (weighted significance)Esterman binocular (weighted significance)FP rate not > 20%FP rate not > 20%

Central missed pointsCentral missed pointsmonocular central fieldsmonocular central fields


DVLA requestDVLA request

• Form to patientForm to patientnotifies them of usnotifies them of us

• Form to usForm to usappointment within appointment within

2 weeks2 weeks

• Vision & VA check Vision & VA check alsoalso


EstermanEsterman• Controlled illumControlled illum• Seen = dotsSeen = dots• Not seen = spotsNot seen = spots• 112 points112 points• FP testedFP tested

Central spots missedCentral spots missedOriginally required Originally required

central fieldscentral fieldsNow some points Now some points

loss acceptableloss acceptable


Age Age vsvs sex distribution sex distribution

05

101520253035

21-30

31-40

41-50

51-60

61-70

71-80

81-90

91-100

Age

Male Female

79 Male 23 Female


CaveatCaveat

• False positiveFalse positive No light presented patient pressesNo light presented patient presses Trigger happy = over estimates fieldTrigger happy = over estimates field

• False negativeFalse negative An artefact occurs when FN tests arise within An artefact occurs when FN tests arise within

area of defectarea of defect Total homonymous hemianopia FP zero FN Total homonymous hemianopia FP zero FN

60%, not possible to reduce60%, not possible to reduce

• ArtefactsArtefacts Noses, spec’s, monocular, lids etc.Noses, spec’s, monocular, lids etc.


Ordinary Driving licenceOrdinary Driving licence• Criminal offence Criminal offence notnot to notify DVLA immediately patient to notify DVLA immediately patient

becomes aware of eyesight condition likely to be a becomes aware of eyesight condition likely to be a source of dangersource of danger Historically Ophthalmology did not do (e.g. COAG, pan Historically Ophthalmology did not do (e.g. COAG, pan

retinal photocoagulation)retinal photocoagulation) Note insurance could be voidNote insurance could be void AOP and MDU will defend breach of confidentiality AOP and MDU will defend breach of confidentiality

• ifif notified in advance & public interest and all other venues notified in advance & public interest and all other venues exhaustedexhausted

GOC also GOC also • appropriate legal advice, public interest defence and record appropriate legal advice, public interest defence and record

keepingkeeping


Chapter 6 Visual DisordersChapter 6 Visual Disorderswww.dvla.org.uk/at_a_glance/ch6visual.htmwww.dvla.org.uk/at_a_glance/ch6visual.htm

Group 1Group 1 Group 2Group 2

AcuityAcuity NPTNPT 6/9 better6/9 better

6/12 worse 6/12 worse

>3/60 unaided>3/60 unaided

CataractCataract Caveat that glare may Caveat that glare may prevent achievement of prevent achievement of NPTNPT

Must meet above, same Must meet above, same caveat re glare appliescaveat re glare applies

Monocular Monocular

VisionVision

Must notify DVLA then Must notify DVLA then must have:must have:

i)i) AdaptedAdapted

ii)ii) NPT & VF passNPT & VF pass

Complete loss or <3/60 Complete loss or <3/60 barred unless GF rightsbarred unless GF rights

Visual Field Visual Field

DefectsDefects

Cease unless meets Cease unless meets national guidelinesnational guidelines

Normal VF requiredNormal VF required

(not defined)(not defined)


Chapter 6 Visual DisordersChapter 6 Visual Disorderswww.dvla.org.uk/at_a_glance/ch6visual.htmwww.dvla.org.uk/at_a_glance/ch6visual.htm

Group 1Group 1 Group 2Group 2

DiplopiaDiplopia Cease on diagnosis.Cease on diagnosis.

Resume on spectacle control or Resume on spectacle control or patching if monocular appliespatching if monocular applies

Recommended permanent Recommended permanent refusal if insuperable.refusal if insuperable.

Patching not acceptablePatching not acceptable

Night Night blindnessblindness

Considered on an individual Considered on an individual basisbasis

Meet Group 2 acuity and VF Meet Group 2 acuity and VF then on individual basisthen on individual basis

Colour Colour

VisionVision

No need to notifyNo need to notify

No restriction No restriction

No need to notifyNo need to notify

No restrictionNo restriction

Blepharo-Blepharo-spasmspasm

Mild can be allowed subject to Mild can be allowed subject to report and DVLA being report and DVLA being informed.informed.

Control with botulinum not Control with botulinum not accepted. accepted.

Refuse or revokeRefuse or revoke


Other aspectsOther aspects• DiplopiaDiplopia

• insuperable = unfitinsuperable = unfit• late onset sudden e.g. stroke desist 1/12 until can tolerate prism late onset sudden e.g. stroke desist 1/12 until can tolerate prism

or occlusionor occlusion

• MonocularMonocular• period of time off period of time off • needs to meet standardneeds to meet standard

• GlareGlare• Problems may not be predicted by VAProblems may not be predicted by VA

• Colour visionColour vision• no requirementno requirement• (protanopes)(protanopes)


Basic Vocational drivingBasic Vocational driving

• 6/9 better eye6/9 better eye

• 6/12 worse eye6/12 worse eye

• Uncorrected VA better than 3/60Uncorrected VA better than 3/60If spec’s dislodged should be able to If spec’s dislodged should be able to

bring to a haltbring to a halt


DVLA websiteDVLA website

• www. dvla.gov.uk

• Details standards

• Vision panel committee meetingsIn camera for cases otherwise open

forum


Colour VisionColour Vision

• DichromatsDichromatsOne of these is missingOne of these is missingProtan. Deutan. TritanProtan. Deutan. Tritan

• TrichromatsTrichromatsOne of these functions One of these functions

poorlypoorlyProtan. Deutan. TritanProtan. Deutan. Tritan


2 4 4 2

8 8 6 3 9 9 3 6

Protan defectsProtan defects

• No long wavelength coneNo long wavelength cone• Look at duochromeLook at duochrome• Loss of absolute sensitivity to redLoss of absolute sensitivity to red

Supra-threshold e.g. D15, CUCVT a Supra-threshold e.g. D15, CUCVT a protan may perform better than deutan protan may perform better than deutan due to luminance cues for reddue to luminance cues for red

Very poor performance at or near Very poor performance at or near thresholdthreshold

Applies to dichromat and trichromatApplies to dichromat and trichromat Not simply colour matching problem Not simply colour matching problem

but one of signal detectionbut one of signal detection

2 4 4 2

8 8 6 3 9 9 3 6


Relative Accident risk Relative Accident risk (Vingrys 2002)(Vingrys 2002)

0 10 20 30

Protanomal

Protanope

0.05 Alcohol

0.08 Alcohol

0.1 Alcohol

0.15 Alcohol

Relative risk

Protan defects 1.7X Potential accident rate 43 compared to 26 per 100,000kmVerriest et al 1980

Protan’s are excluded from professional driving in Victoria, Australia


Driving and Low Vision !Driving and Low Vision !

• Is PS registration incompatible with Is PS registration incompatible with driving ?driving ?

• USA experienceUSA experienceRestricted licencesRestricted licencesBioptic telescopes permitted in 38 statesBioptic telescopes permitted in 38 states• California has 229 bioptic drivers out of 21 California has 229 bioptic drivers out of 21

million othersmillion others• No sig diff in accident ratesNo sig diff in accident rates• Add 3 accidents to the 1.1 million per year.Add 3 accidents to the 1.1 million per year.


ConclusionConclusion

• Time has come for the UK to Time has come for the UK to consider BiOpticsconsider BiOptics

• Legislatively unlikely to occur in Legislatively unlikely to occur in isolation to Europeisolation to Europe

• No absolute bar to use ?No absolute bar to use ?

• Would have to pass standards as Would have to pass standards as discusseddiscussed


Thanks for listening Thanks for listening

optometric educators ltd driven to distraction bioptic driving conference 21 st june 2004 nick...

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