Transcript DVLA Standards

“But I only drive to the
shops…”
Mr Javeed Khan
Consultant Ophthalmologist
St 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
Peripheral
Fixation
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 fields
Can 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
P610VOH
M528CBY
T174ILE
P610VOH
M528CBY
Kiel et al 2003
McMonnies 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 metres
What must the patient do?
Stop driving
Offer to surrender license to DVLA
Apply 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
350
Horizontally +/- 75 degrees
Superior 35 degrees
Inferior 55 degrees
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
600
600
500
700
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
Allowed
Cluster of 3 on or across horizontal
Limit of field
measured at
this point
(750)
Limit of field
measured at
this point
(500)
Peripheral defects
Allowed
Cluster of 3 on or across horizontal
Vertical 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 Driving
Notify DVLA
DVLA 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 impairment
And
Full functional adaptation
And
Satisfactory 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
Coping with reduced functions
Self-imposed limits
Advantage of experience: Diminishes with increasing
impairment due to age
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 adapt
Inform 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: RESULTS
Lutein and Zeaxanthin
No benefit over AREDS original
But:
• If beta-carotene removed and replaced with
Lutein + Zeaxanthin
• Further 18% risk reduction
Also:
• If low dietary Lutein and Zeaxanthin
• 25% risk reduction with supplement
AREDS 2: RESULTS
Beta-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: RESULTS
Zinc
• 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 mg
Vitamin E: 400 IU
Lutein: 10 mg
Zeaxanthin: 2 mg
Zinc: 25 mg
Copper: 2mg
Serous PED: CSR
Serous PED: AMD
Vitelliform
Haemorrhagic PED