“but i only drive to the shops…” mr javeed khan consultant ophthalmologist st mary’s...

“But I only drive to the shops…”Mr Javeed Khan

Consultant OphthalmologistSt Mary’s Hospital

Isle of Wight

Driving standards

What is the evidence?

Age and Driving

Monocular drivers

Dilated pupils

Do these patients need to notify DVLA?

• 45 year old with ocular hypertension

• 68 year old bilateral glaucomatous field loss

• 75 year old with glaucoma, field defects in one eye only

• Lorry driver on Latanoprost, mild field loss in one eye

• Lorry driver with colour blindness

• 42 year old with night blindness

Driving is a demanding activity

PERCEPTION Central Fixation

Peripheral Scanning

INTERPRETATION

Reaction Time

DECISION

ACTION Motoring Ability

Is Poor Visual acuity a contributory factor

in road accidents?

Is poor visual acuity a contributory factor in road accidents?

From 2005 – 2009 nearly 700,000 accidents on UK roads•0.4 % of fatal accidents and 0.2 % of all accidents due to ‘defective/uncorrected eyesight’

How important is poor vision as a contributory factor in road accidents?

From 2005 – 2009 nearly 700,000 accidents on UK roads•0.4 % of fatal accidents and 0.2 % of all accidents due to ‘defective/uncorrected eyesight’

•Mobile phone use 0.2 % of all accidents

How important is poor vision as a contributory factor in road accidents?

From 2005 – 2009 nearly 700,000 accidents on UK roads•0.4 % of fatal accidents and 0.2 % of all accidents due to ‘defective/uncorrected eyesight’•Mobile phone use 0.2 % of all accidents•‘Failed to look properly’ 20% of fatal and 35% of all accidents•Vision affected by sun/headlights/dirty windscreen 3.5%

VISUAL STANDARDS FOR DRIVING

With both eyes open and with the aid of glasses or contact lenses if worn:•Can read number plate at 20 metres in good daylight•Snellen visual acuity 6/12 or better

Group 2 (Lorry, Bus)

Snellen visual acuity:•Better eye 6/7.5•Before 2012: Worse eye to be at least 6/9•Now 6/60 acceptable in worse eye•No minimum uncorrected visual acuity•But glasses no more than + 8 dioptres

Case

• Lorry driver develops posterior sub-capsular cataract in left eye, Right eye pseudophakic

• VA: • Right eye: 6/6 unaided• Left eye: 6/36 unaided no improvement• Both eyes open: 6/6

• Patient doesn’t complain of glare, has full fieldsCan he continue to drive his lorry while waiting for

cataract surgery? Yes, as long as no other visual impairment

Evidence for visual acuity standard:Why 6/12 on Snellen?

In 1937 standard introduced:Number plate at 75 feet (23 metres)Equal to stopping distance at 30 mph

Evidence for visual acuity standard• As number plate sizes changed distance changed:

• 20.5 metres pre-2001

• 20 metres Current

Evidence for visual acuity standard:Why 6/12 on Snellen?• Drasdo and Haggerty 1983:

• Approximates to 6/9-2 or 6/10 based on their statistical model

• Charman 1997:

• Calculated Snellen equivalent as 6/15 based on angular subtense (13.4 minutes of arc)

• Current standard 6/12

How reliable is the Snellen standard in predicting number plate test results?• Currie et al BJO 2000

• 100 patients with vision 6/9 or 6/12

• Ability to read number plate tested

• 26 % of 6/9 FAILED and 34% of 6/12 PASSED

Number plate difficulty

T174ILE M528CBYP610VOH

T174ILE P610VOH M528CBY

Kiel et al 2003McMonnies 1999 (Chart construction and letter legibility)

Does poor visual acuity cause accidents?

Is there a link between poor visual acuity and accidents?The evidence is WEAK from studies of accidents

Greater likelihood of involvement in more than 1 accident if VA poor (Hofstetter et al 1976)

Weak correlation between driving and VA

(Burg et al 1976)

Is there a link between poor visual acuity and accidents?

Studies of accidents:Studies not big enough to pick up statistical difference

• Motor accidents are rare

Owens et al: not likely to fall victim to fatal accident if drive for 3738 years

• Extremes of vision in drivers is rare

•People exhibit adaptive behaviour•Confounding variable e.g. glare from cataract

Is there a link between poor visual acuity and accidents?Studies on closed road circuits:

•Poor acuity affected sign recognition and hazard avoidance

•Increased time to complete circuit

But

•No impact on manoeuvring ability or maintaining lane position

Studies on simulators

•In different conditions: support the findings from closed circuit studies

Is there a link between poor visual acuity and accidents?Effect of Legislation:In Florida mandatory rescreening introduced for over 80s

Those that failed were given an opportunity to correct vision (glasses, cataract surgery etc.)

Most were able to go back to driving after correction

After 3 years:

Accident fatality rates in over 80s fell by 17%

Case

• Patient has cataracts• VA:

• Right eye: 6/18, Left eye: 6/24• Both eyes open: 6/12-3

• Patient can read number plate in good light at 20 metresWhat must the patient do?Stop drivingOffer to surrender license to DVLAApply for restoration after successful cataract surgery

Is there a link between visual field loss

and accidents?

Evidence for Visual Fields and accidents

• People with visual field defects have DOUBLE the

number of accidents/traffic violations

• Half of the people with field loss were unaware of

problems with peripheral vision

• Johnson and Keltner (1983) in a study of 10,000 drivers

Evidence for Visual Fields and accidents

• Visual field size best predictor of real-world and

simulator crashes and driving performance

• Especially defects within 100 degrees

• But actual cut-off value for standards is unclear

VISUAL FIELDS

Tested with:

•Target equivalent to white, Goldmann III4e settings

•Esterman binocular field (sometimes Monocular fields exceptionally Goldmann)

•False positive no more than 20%

Esterman Binocular Field

120 points

Suprathreshold 10dB

Esterman Binocular Field

Horizontally +/- 75 degrees

Superior 35 degrees

Inferior 55 degrees

350

550

Esterman

• Central +/- 20 degrees

Sparse

12 points above and

22 below fixation

VISUAL FIELDS

STANDARDS:

•Field of at least 120 degrees on the horizontal

•Minimum 50 degrees to left and right

750 450

500 700

600600

VISUAL FIELDS

STANDARDS:

•No significant defect in central 20 degrees of fixation above and below horizontal

Central defects

•Allowed

• Scattered single missed points

• Single cluster of up to 3 adjoining points

Central defects

•Not Allowed

• Cluster of 4 even partly within central 20 degrees

• Cluster of 3 and additional single

• Central extension of hemianopia/quadrantonopia

greater than 3 points

Peripheral defects

AllowedCluster of 3 on or across horizontal

Limit of field measured at this point (500)

Limit of field measured at this point (750)

Peripheral defects

AllowedCluster of 3 on or across horizontalVertical defect of any length but single point width

cutting across horizontal

Limit of field measured at this point (750)

Limit of field measured at this point (500)

Pass?Limit of field measured at this point (750)

Limit of field measured at this point (500)

Limit of field measured at this point (750)

Limit of field measured at this point (500)

Case

Patient must:Stop DrivingNotify DVLADVLA will arrange Esterman, license may be revoked

After 12 months: May re-apply as an exceptional case if:Non-progressive, no other ocular pathology or impairmentAndFull functional adaptationAndSatisfactory practical driving assessment

Problems with Esterman fields

‘Only 25% of measured points fall within the most functionally relevant area’Rauscher et al, UK department of transport 2007

Esterman field problems

•Too many inferior points

•Many points on right side periphery

irrelevant for RHD cars

Superior v Inferior field defect simulation

• Hazard perception test score: Significantly worse with superior defect than with inferior

• Crabb et al in a study of 30 UK drivers

Esterman field problems

•Stimulus too bright in centre

•No points tested in central 7.5 degrees

Esterman field problems

• Difficulty with fixation monitoring• Too lenient?• Alternatives in the future:• Humphrey fields integration• Traffic algorithm

Other relevant tests for visual function

• Contrast Sensitivity

• Glare Sensitivity

• Useful Field of View (UFOV)

Other relevant tests for visual function

• Contrast Sensitivity

• Grey letters against white background

• Simulates night driving ( e.g. ‘detecting dark coated

pedestrian at night’)

• Stronger correlation with crashes than visual acuity

Martoletti et al 1998, Dunne et al 1998 TWICE the risk

Other relevant tests for visual function

• Contrast Sensitivity

• Pelli Robson

• But no normative database

across centres

• No accepted cut-off values

Other relevant tests for visual function

• Glare Sensitivity

• Sensitivity to glaring light sources (setting sun, headlights)

• Increased relative risk of accidents (von Hebenstreit 1995,

Lachenmayr 1998)

• But no established methods (Straylight measurement being

developed) or adequate cut-off values

Other relevant tests for visual function

• Useful Field of View (UFOV)

• Tests ability to perform simultaneous detection tasks

• Combines visual task with neuro-psychological task

of attention

• Predicts fitness to drive

Identify Central target

Localize additional target

With Distractors

Problems with UFOV

May be difficult to interpret

Expensive

Performance may improve with practice

Age and Driving

Driving and the older driver

• Decline in sensory, cognitive and motor function• Increased reaction time• Reduced motoring ability

• Reduction in Contrast sensitivity• Difficulty seeing road signs

• Visual acuity, Visual field sensitivity and stereoacuity• Problems at intersections

• Increased glare sensitivity• Difficulty seeing road markings

• Increased cataract, AMD and glaucoma• Personality: Increased hesitancy

Useful Tests in older drivers

Self-imposed limits

Advantage of experience: Diminishes with increasing impairment due to age

Coping with reduced functions

Advantage of experience: Age group 40-60

Compensates for impairments but at the cost of increased stress

Accidents by age

Accidents by age

Older drivers more likely to have:

•Multi vehicle accidents

•Fatal accidents

•Accidents in inner city roads not on country roads

•Accidents at junctions and intersections• Failure to give way• Right turns

If standards met but driver unsure

• Self-regulation

• Family and friends

• Driving assessed in a confidential and objective

test from Royal Society for the Prevention of

Accidents (RoSPA)

Who needs to inform DVLA:(Failure to inform: £1000 fine and possible prosecution if accident)

STOP DRIVING:

•Any condition if fail to meet visual standards

•Bilateral field defects

e.g. hemianopia, quadrantonopia, glaucomatous

•Diplopia

Who needs to inform DVLA:(Failure to inform: £1000 fine and possible prosecution if accident)

• Bilateral conditions even if standards achieved

• Glaucoma, Diabetic retinopathy, AMD, BRVO, cataract

• If both eyes affected

• Inform DVLA if:

• Laser in both eyes

• Vision problems in both eyes

Do these patients need to notify DVLA?

• 45 year old with ocular hypertension No

• 68 year old bilateral glaucomatous field loss Yes

• 75 year old with glaucoma, field defects in one eye only No

• Lorry driver on Latanoprost, mild field loss in one eye Yes

• Lorry driver with colour blindness No

• 42 year old with night blindness Yes

Who needs to inform DVLA:(Failure to inform: £1000 fine and possible prosecution if accident)

• Blepharospasm: cannot drive if severe

• Night blindness: considered on individual basis

• Nystagmus

• Optic Neuritis/atrophy

• Tunnel Vision

DIPLOPIA

• Cease driving at diagnosis

• Inform DVLA

• Resume driving after confirming to DVLA that diplopia controlled with glasses/patch

If patch must satisfy conditions for monocularity

• Exception:

• Stable diplopia of 6 months or more: uncorrected

If consultant support indicating satisfactory functional adaptation

QUAD BIKES

Anyone got a spanner?

Mobility Scooters

• Class 3 can be driven on roads

maximum speed 8 mph

• Recommended that should be

able to read number plate at

12.3 metres (40 feet)

Monocular Drivers

• Limited peripheral vision nasally 20-40 degree deficit• Saccades and head rotation to compensate

• Physiological blind spot: 2 metres size at 20 metres distance• Effect diminished by Ocular re-fixation (average 3 times/second) and• Head movements BUT• Small objects may remain unseen for longer

• Lack of stereopsis• Uncertain relationship with crash rates

• Risk of one eye temporarily losing sight due to FB, watery eye

Are monocular drivers unsafe?

• Accidents• Johnson and Keltner: Same crash rates

• Closed-course study of driving performance• Woods et al: Driving no worse

• Simulator studies• McKnight et al: No significant safety issues

• However• Liesmaa: more dangerous behaviour at junctions and while

overtaking

Monocular drivers: Formula One (eye) or Two

Case 5

• Patient diagnosed with choroidal melanoma• Right eye enucleated• Left eye: VA: 6/6, Full fields

• Patient can read number plate in good light at 20 metres

How does this affect driving? Must adaptInform insurers?Does the patient need to notify DVLA? No need

DVLA requirements for monocular drivers

• Visual Acuity Snellen 6/12

• Number plate at 20 metres

• Same standard for visual fields

• Can drive when ADAPTED to the condition

• NO need to notify DVLA

Dilated Pupils

• Cycloplegia • Reduced distance VA in high hypermetropes

• Spherical Aberrations:• 9 times increased aberration

• Glare, dazzle

Study of daytime driving in dilated patients on closed circuit: 1% Tropicamide• Vision measures

• Visual Acuity reduced: average 2 letters maximum 1 line• Contrast Sensitivity worse: average 1 letter maximum 4 letters• Glare sensitivity worse: average 4 letters

• Driving measures• Significantly worse for: potholes, road debris, speed bumps,

pedestrians, other vehicles• No problems with: Road signs, traffic cones, gap perception

Dilated Pupils

• Potamitis et al on driving simulator studies:• Reduced High Contrast Visual Acuity• Reduced Contrast Sensitivity

BUT Driving not impaired

• But remember: they used driving simulator, no glare, young patients, no ocular disease

• Likely to be worse in older people, at night, foggy conditions, with cataract/AMD

• Insurance Implications?

Electric cycle:

Segway

QUESTIONS?

Fields for class 2 drivers

Action to be taken if patient ignores your advice and continues driving

• Explain to patient:• 1. Their eye condition may affect ability to drive• 2. They have a legal duty to inform DVLA

• If patient refuses to accept advice:• Suggest second opinion, help to arrange and advise to STOP driving until then

• If continues to drive:• Reasonable effort to persuade them to stop• Discuss with relatives/carers/friends with patients permission

• If all fails:• Inform patient that you intend to write to DVLA• Inform DVLA confidentially on ‘Doctor Notification’ form• Let patient know you have informed DVLA

AREDS 2

AREDS 2: BACKGROUND

AREDS 1 showed 25% reduction in risk of advanced AMD•AREDS 1 formula had

• Carotenoid: beta carotene• Anti-oxidants: Vitamins C and E• Minerals: Zinc and copper

But:•Concern about risk of beta carotene in smokers•Side effects of zinc at high doses•No lutein, zeaxanthin, omega 3 FA

AREDS 2: OBJECTIVES

Effects of high supplemental doses of:• dietary xanthophylls (lutein and zeaxanthin)• and omega -3 fatty acids on• the development of advanced AMD • cataract and • moderate vision loss (the loss of 15 or more letters). Effects on the development and progression of AMD of:• eliminating beta-carotene in the original AREDS formulation• reducing zinc in the original AREDS formulation

AREDS 2: RESULTS

Omega 3 Fatty Acids

No benefit over AREDS original

AREDS 2: RESULTSLutein and Zeaxanthin

No benefit over AREDS originalBut:•If beta-carotene removed and replaced with Lutein + Zeaxanthin

• Further 18% risk reductionAlso:•If low dietary Lutein and Zeaxanthin

• 25% risk reduction with supplement

AREDS 2: RESULTSBeta-Carotene

• Removing beta-carotene did not compromise efficacy of formula

• Better without beta-carotene if Lutein and Zeaxanthin added

• Increased risk of lung cancer even in FORMER smokers

AREDS 2: RESULTSZinc

• Reducing zinc did not compromise efficacy of formula

• But no certainty about what is the best dose

AREDS 2:Implications for clinical practice• Drop beta-carotene• Add Lutein and Zeaxanthin• No need for omega 3• Reduce zinc to 25 mg• Keep the rest as before

Same formulation for all (smokers included)

Vitamin C: 500 mgVitamin E: 400 IULutein: 10 mgZeaxanthin: 2 mgZinc: 25 mgCopper: 2mg

Serous PED: CSR

Serous PED: AMD

Vitelliform

Haemorrhagic PED