"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/