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"Impaired vision does not excludepractical fitness to drive"
Aart C. Kooijman, Wiebo W. Brouwer,
Ruud A. Bredewoud, Tanja R.M. Coeckelbergh,
Frans W. Cornelissen, Mark L.M. Tant
Groningen, The Netherlands
University of Groningen
Visio
CBR
Study on
Practical Fitness to Drive
of
Subjects
with
Central or Peripheral Visual Field Defects.
Free publicity in the newspapers
Inclusion Criteria and Tests
• inclusion: 0.1 < VA < 0.5 and / or
horizontal VF < 1200
driving experience > 100 000 km
no cognitive impairment (MMSE, Bell’s Test)
ophthalmic screening
• visual function: refraction, VA, VF, CS, DA, stereopsis
• visual attention: UFOV-like, AFOV, fixation and saccades
• practical fitness to drive assessment on the road
• driving test in a driving simulator
• practical fitness to drive assessment on the road
Assessment of practical fitness to drive
intermediate level
between
medical fitness to drive
and
driving skill
On-road driving test for assessment of
practical fitness to drive
• Evaluation by an expert in
assessing on-road driving in
handicapped persons
– using candidate’s own car, if possible– in the regional area of the candidate– comprises city, rural, and highway driving
On-road driving test for assessment of
practical fitness to drive
• It is evaluated
whether someone
can drive fluently and safely
given
his/her impairments and
including use of compensations and adaptations
Assessing practical fitness to drive
• Test Ride to Investigate Practical Fitness to Drive (TRIP) comprises tactical and operational aspects:
• lateral position control• following distance• speed control• visual scanning and viewing behaviour• perception of traffic signals• passing and overtaking• use of car controls• anticipation and traffic insight• interaction with other traffic participants
Assessing practical fitness to drive
• Test Ride to Investigate Practical Fitness to Drive (TRIP) comprises tactical and operational aspects:
• Mostly 4-point-rating scales on each item• Most aspects broken down to specific situations
Scores derived from TRIP• Operational score
(mechanical handling and dealing with external stimuli)
• Tactical score (choice of manoeuvres, safety margins, anticipation)
• Visual score: operational and tactical items with a visual (scanning) component
• Total score: average of all TRIP items
• Global score:
final expert judgement:
fit or unfit
100 Subjects
Central Peripheral Central andPeripheral
Mild
visual acuity (logMAR)
horizontal fielddiameter* (deg)
male : female
age # year (SD)
driving license # year (SD)
(n=24)
0.23(0.64)
142
16:8
65 (13)
38 (11)
(n=36)
0.74(0.14)
84
29:7
60 (12)
37 (10)
(n=7)
0.19(0.72)
91
4:3
63 (15)
39 (17)
(n=33)
0.77(0.11)
141
14:19
67 (9)
38 (8)
* Goldmann III4 isopter
Visual Field Defect
0 20 40 60 80 100 120 140 160 180
Visual Field Diameter (ODS) Goldmann III 4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Vis
ual
Acu
ity
(OD
S)
Passed
Failed
Central + Peripheral
Mild62% passed
Central25% passed
Peripheral42% passed
Percentage passing the Practical Fitness to Drive Testvs
Visual Acuity
1114
0
20
40
60
80
100
Per
cen
tag
e p
asse
d
18
17
23
2
4
9
0 0,5 1 1,5 2Decimal Visual Acuity
1114
Of our population
25% of the
subjects with
VA < 0.5
is
“Fit to Drive”
100 subjects
Percentage passing the Practical Fitness to Drive Testvs
Visual Field Diameter
0 20 40 60 80 100 120 140 160 180 200Visual Field Diameter (degree)
0
20
40
60
80
100
Per
cent
age
pass
ed
100 subjects
6
3118
33
6
8
18
4
In our population
visual field diameter
shows
a weak relation
with
“Fitness to Drive”
33
6
8
18
4
Predictive power (regression analysis)
pass/fail Practical Fitness to Drive test
predictor
model 1
visual acuity (logMAR)
visual field (VFS)
explained variance R2
.20
.24
predictor
model 1
visual acuity (logMAR)
visual field (VFS)
AFOV, threshold presentation time
model 2
visual attention (UFOV-like)
contrast sensitivity (log CS)
age
.20
.24
.32
.23
.34
.34
Predictive power (regression analysis)
pass/fail Practical Fitness to Drive test
explained variance R2
Predictive power (regression analysis)
pass/fail Practical Fitness to Drive test
Contribution of
driving simulator performance
180 degree horizontal field ‘3 km in town centre’
‘15 km on a 2-lane road’‘20 km on a highway’
14 intersections
0 20 40 60 80 100 120 140 160 180
Visual Field Diameter (ODS) Goldmann III 4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Vis
ual
Acu
ity
(OD
S)
Central + Peripheral
Mild62% passed
Central25% passed
Peripheral42% passed
peripheral visual field defect
accidents: 23%
Results in the driving simulator
mild visual field defect
accidents: 9%
central visual field defectaccidents: 35%
predictor
model 1
visual acuity (logMAR)visual field (VFS)AFOV, threshold presentation time
.20
.24
.32
Predictive power (regression analysis)
pass/fail Practical Fitness to Drive test
explained variance R2
.38
model 2
visual attention (UFOV-like)contrast sensitivity (log CS)age
.23
.34
.34 .35
plus driving simulator variables
plus driving simulator variables
.47
.45
Conclusions
• a considerable percentage of the subjects demonstrated to drive safely
• selection based on vision, attention and driving simulator data exclude many people who are fit to drive
• selection based on the performance on the task itself (driving) seems to be more fair
General Conclusion:
• Compensatory Driving Behaviour has to be assessed in
an Practical Fitness to Drive test
• study 1:
http://www.ub.rug.nl/eldoc/dis/medicine/t.r.m.coeckelbergh/
• study 2:
http://www.ub.rug.nl/eldoc/dis/ppsw/m.l.m.tant/