Simulator based assessment of drivers with visual field

Simulator based assessment of drivers with visual field defects Björn Peters, VTI

Sweden – some basic facts • • • EU member state EU driving license directive – specification of minimum medical requirements 9. 6 million inhabitants 6. 1 million driving license group 1 1. 6 million license holders +65 y 40 000 revoked licenses (all reasons) (2013) 4 500 revoked licenses for medical reasons annually (2013) ? ? due to visual problem 100 applications for exemptions annually

Swedish requirements for peripheral visual field Group I Binocular Esterman screening test 2018 -03 -19 3

Swedish requirements for central visual field Group I Static threshold perimetry (Humphrey 24 -2 or equivalent) Within 10° from fixation: Threshold in each corresponding test point should be 20 d. B or more Within 20° from fixation: Threshold in each corresponding test point should be 10 d. B or more (one missing point is accepted) 2018 -03 -19 4 ≥ 10 d. B ≥ 20 d. B

The process in Sweden • • Mandatory for all physicians to report if medical requirement not fulfil or agree with the patient to refrain from driving (written consent) Swedish Transport Agency (STA) decides if requirements fulfilled –> OK, If not -> revoked license Agree -> apply for exemption or Disagree -> appeal in court 3 levels Apply for exemption -> added evidence of fitness to drive required e. g. • Simulator Based Assessment in Norway - SINTEF • On-road assessment not sufficient • Demand for a new Simulator Based Assessment Method § License with exemption – conditions can apply e. g. geographical restrictions (2012 – 103, 2013 – 110)

Simulator test at SINTEF – reaction time 6 positions – rural road 1 Press buttons to respond 6 positions – rural road 1 Results compared to normative data 11 positions – city road 1 Reaction times were recorded from 20 stimuli over a 15 minutes drive. Stimuli size: 1. child head at 30 m, 2. adult body at 30 m, Stimuli: duration 4 seconds

Developing a new assessment method at VTI • • • Aim: determine if a driver with a visual field loss can compensate and drive equally well as a driver without field loss Approach: develop a relevant and realistic diving task with more or less critical situations and build a matched reference database (100+) Simulator: high end simulator, dynamic, good visual system Consider: simulator sickness and test conditions Output: certificate stating driving performance/ability compared to normative data Assessment Validity: continuous follow-up and improvements

Simulator based assessment - pros and cons Strengths High level of control Good internal validity Same conditions for all Critical situations with no risk Realistic compared to clinical testing Reliable S-R testing Eye tracking feasible Weaknesses Simulator driving - 3 D in a 2 D world Speed perception not ideal – offset Situations simplified compared to real life External validity partly good – follow up needed Simulator sickness

VTI Driving Simulator IV - Volvo XC 60 cabin Rear- and Side. Mirror Displays 4 Video Cameras Virtual Cockpit Display Sound System Rexroth hexapod X-Y Sled 2, 3 * 2, 5 m 5 Gaze Tracking Cameras Shaker Force Feedback Steering Wheel

Sim IV visual projection system 9 x Epson EB-410 W projectors Mersive SOL software § Auto calibration § Edge blending § Color correction >180 degree field-of-view Tillfälle att prova under dagen

Driving task and assesment criteria • Approx. 50 km driving (rural, motorway, city) • Critical situations (pedestrians, vehicles, bicycles, road works, traffic light etc. ) • Assessment measures: speed, time, lateral position, (collisions/incidents) • Also: Time based safety margins (combination of TTC and THW) • Reaction time to artificial stimuli (SINTEF like) • Tentative assessment criteria exclude 2, 5% of “low performers” (previously used at SINTEF) - several measures Tool for development, runs on a PC

SINTEF test - proposal • • Motive: compare data with SINTEF and other studies Stimuli as SINTEF – traffic signs in 6 different positions (false and true (STOP sign)) Simultaneous stimuli – right/left – controlling for over compensation Two buttons on the steering wheel • One true stimuli (also combination with false) – press one button • Two true stimuli – press two buttons • One single or two false stimuli – press no buttons • • • Separate part of the driving task Clear written and oral instructions Training before

Defining assessment criteria – a difficult task v Considering own and other road users’ safety v Not restrict if driving ability deemed sufficient v No solid scientific evidence for how much we need to see in order to drive safely v Other examples v. Alcohol (BAC - 0, 2‰) fixed – should it be differentiated? v. Deafness OK to drive – why? v. Epilepsy – OK with medication and no seizure for 3 months v. Dementia – when is the right time to stop? v. Mobility impairments – what is sufficient adaptation? v Whatever we do we need to follow-up!

Visual and cognitive tests • • • Visual acuity Visual field of view test - Humphrey Useful Field of View (UFOV) Trail Making Test (TMT A&B) Dynamic TMT (New) Perceptual speed (Operative) Attentional demanding (Operative/Tactical) Working memory (Tactical/strategic) Meta memory (Strategic) Useful field of view (UFOV) Dynamic Trail Making Test

Persons with visual field defects interested to participate Until 15 April 222 interested 189 replied a short survey Data for recruiting 100 reference drivers Most have sent their visual field data Select a small, relevant group of drivers to participate in the project • Delivery date mid - 2014 • • •

Age, gender, experience for selection of reference drivers Age 18 -24 25 -34 35 -44 45 -54 55 -64 65 -74 75 Total Male Female Total 4 1 5 1 1 2 12 9 21 22 5 27 36 8 44 63 2 65 25 0 25 163 26 189 Most male, < 70% 55 + Age 18 -24 25 -34 35 -44 45 -54 55 -64 65 -74 75 Totalt Num 5 2 21 27 44 65 25 189 Median distance km/week 40, 0 202, 5 250, 0 300, 0 200, 0 150, 0 200, 0 Min 10000 km/y Max 25000 km/y

Diagnoses Diagnosis, free Stroke Glaucoma Diabetes Eye injury Brain tumor Other Total Missing Totalt Num 69 60 21 17 7 4 178 11 189 % 36, 5 31, 7 11, 1 9, 0 3, 7 2, 1 94, 2 5, 8 100, 0 % of those with a diagnosis 38, 8 33, 7 11, 8 9, 6 3, 9 2, 2 100, 0 Cumulative % of those with a diagnosis 38, 8 72, 5 84, 3 93, 8 97, 8 100, 0 Select based on diagnosis and visual field defect

Difficult driving situations

Questions, comments?