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Effect of compensatory viewing strategies
on practical fitness to drive in subjects with visual field defects
caused by ocular pathology.
Tanja CoeckelberghW.H. Brouwer, F.W. Cornelissen, A.C. Kooijman
University of Groningen, The Netherlands
current address:
University Hospital Antwerp, Belgium
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Bioptic telescopes are intended for
•detailed vision (street names, signs, etc.)•not for regular driving
are subjects with decreased visual acuity able to drive safely?
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SubjectsSubjectscentral VFD
(n=24)
peripheral
VFD (n=36)
central and
peripheral (n=7)
mild VFD
(n=33)
vision parameters
visual acuity (logMAR) 0.64 (0.03) 0.14 (0.02) 0.72 (0.08) 0.11 (0.02)
horizontal field *(°) 142 (13) 84 (35) 91 (35) 141 (13)
sample characteristics
male : female 16:8 29:7 4:3 14:19
age 65 (13) 60 (12) 63 (15) 67 (9)
driving license (# years) 38 (11) 37 (10) 39 (17) 38 (8)
* Goldmann III4 isopter
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On-road driving testOn-road driving test
•own car•own neighbourhood•official driving examiner (CBR)•1 hour•score: viewing behaviour, lateral position,
anticipation, changing lanes, turning left, …
pass/fail score
www.cbr.nl
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On-road driving testOn-road driving test
central VFD mild VFDpassed: 6 (25%) 21 (64%)
unfit to drive: 5 (21%) 0 (0%)not yet fit to drive: 13 (54%) 12 (36%)fit to drive, limited: 6 (25%) 9 (27%)fit to drive: 0 (0%) 12 (36%)
UZ AntwerpUZ AntwerpPercentage of subjects passing TRIP items:
central VFD mild VFDlateral position 66.7 84.8lane choice 70.8 66.7car following 95.8 97.0speed 66.7 69.4viewing behaviour 33.3 39.4detection of traffic signs 58.3** 93.9overtaking 45.8 72.7mechanical operations 75.0 84.8anticipatory behaviour 37.5 63.6communication 45.8 78.8turning left 37.5 51.5merging into another lane 37.5 57.6
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Driving simulatorDriving simulator
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Central VFD
(n=23)
Mild VFD
(n=23)
visual acuity (dec. not.) 0.24 (0.09) 0.83 (0.27)
horizontal field extent*( ) 142 (14) 142 (14)
* Goldmann I I I 4 isopter
Driving simulator: subjectsDriving simulator: subjects
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Driving simulator: resultsDriving simulator: resultscentral VFD mild VFD
speed (km/h) 67(9)** 74(9)lateral position SD (m) n.s.thw-average n.s.thw-minimum n.s.ttc-minimum (log) 0.61 (.16)**0.70 (.15)breaking dti n.s.release accelerator dti n.s.accident (% drivers) n.s.
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1.3
1.4
1.5
1.6
1.7
1.8
1.9
50 km/h 80 km/h left curve 80km/h
right curve 80km/h
path
late
ral p
ositi
on
central VFD
peripheral VFD
mild VFD
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-0.2
-0.1
0
0.1
0.2
0.3
0.4
constant variabledriving speed of lead car
log
THW
min
central VFDperipheral VFD
mild VFD
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Compensatory behaviourCompensatory behaviour
viewing behaviour – pass/fail scorecentral VFD: no relationship
speed – pass/fail score:central VFD: drive more slowly =>
pass
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Conclusions before trainingConclusions before training
On-road driving test: detection of traffic signs was (too) late
Driving simulator:decreased driving speed (compensation)shorter following distancelateral position independent of road curvature
bioptics!
bioptics?
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TrainingTraining
aim: teach compensatory viewing strategies
• laboratory training computer based tasks
• mobility training while walking or cycling
• motor traffic training while driving a car
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AFOVAFOV
60 degrees
24 degrees
-15-10-505
1015
-30 -20 -10 0 10 20 3001234
threshold presentation time (s)
Dependent variables:mean threshold presentation timevariation (PDM)
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SubjectsSubjects
motorlaboratory mobility traffic
central VFD 5 5 7peripheral VFD 6 8 7centr+periph VFD 2 2
1mild VFD 3 1 4
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AFOVAFOV
0
0.1
0.2
0.3
0.4
pre1 pre2 post1 post2assessment
log
thre
shol
dpr
esen
tatio
n tim
e
0
20
40
60
80
100
PDM
thresh. present. timePDM
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Driving simulatorDriving simulator
0
10
20
30
40
50
60
70
pre1 pre2 post1 post2session
num
ber o
f hea
d m
ovem
ents
0
5
10
15
20
25
30
dist
ance
to in
ters
ectio
n (m
)
numberdti
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On-road driving testOn-road driving test
0
0.5
1
1.5
2
2.5
pre1 pre2 post1 post2session
view
ing
beha
viou
r (0-
3)
laboratorymobilitymotor traffic
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On-road driving testOn-road driving test
0
10
20
30
40
50
60
function mobility motor traffictraining
% p
ass
pre2post1post2
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Positive training results:• compensatory viewing behaviour (AFOV)• viewing behaviour while driving • practical fitness to drive (pass/fail score)
• best results: motor traffic training
Conclusions after trainingConclusions after training
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Central VFDCentral VFD
before training: 6/24 passed on-road driving test
training: 17/24 (14 failed, 3 passed)
after training: 8/17 passed on-road driving test
(5 had failed before training)
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ConclusionConclusion
• Are subjects with decreased visual acuity due to a central visual field defect able to drive safely? Yes, 11/24 (46%) passed on-road driving test.
• Might bioptic telescopes be helpful to these subjects? Yes, to improve ‘detection of traffic signs’ and ‘following distance’.
