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STABLE trial of spectacle provision and driving safety among myopic motorcycle
users in Vietnam: study protocol for a stepped-wedge, cluster randomised trial
Download PDF
Download PDF
* Study protocol
* Open access
* Published: 18 December 2024

STABLE TRIAL OF SPECTACLE PROVISION AND DRIVING SAFETY AMONG MYOPIC MOTORCYCLE
USERS IN VIETNAM: STUDY PROTOCOL FOR A STEPPED-WEDGE, CLUSTER RANDOMISED TRIAL

* Vinh Chi Le ORCID: orcid.org/0000-0001-6008-75721,2,
* Kien Gia To ORCID: orcid.org/0000-0001-5038-55842,
* Van Dat Le3,
* Le Nguyen4,
* Graeme MacKenzie ORCID: orcid.org/0000-0001-6995-85575,
* Lovemore Nyasha Sigwadhi6,
* Prabhath Piyasena ORCID: orcid.org/0000-0002-0236-01017,
* Mai Tran4,
* Ving Fai Chan ORCID: orcid.org/0000-0002-4968-79531,
* Rohit C. Khanna ORCID: orcid.org/0000-0002-8698-55626,8,9,10,11,
* Mike Clarke ORCID: orcid.org/0000-0002-2926-72571,12,
* Lynne Lohfeld ORCID: orcid.org/0000-0003-4711-73051,
* Heather Dickey13,
* Augusto Azuara-Blanco ORCID: orcid.org/0000-0002-4805-93221,
* Asha Latha Mettla6,
* Sridevi Rayasam ORCID: orcid.org/0009-0006-3577-38226,
* Han Thi Ngoc Doan2,
* Dung Van Do2,
* Phuoc Hong Le2,
* Charlie Klauer14,
* Richard Hanowski14,
* Zeb Bowden14,
* Lynn Murphy ORCID: orcid.org/0000-0001-9263-633712,
* Joanne Thompson12,
* Susan McMullan12,
* Cliona McDowell ORCID: orcid.org/0000-0002-7644-719712,
* Raja Narayanan6,
* Julie-Anne Little ORCID: orcid.org/0000-0001-5242-806615,
* Huong Thu Ha16,
* Sangchul Yoon17,
* Rahul Goel ORCID: orcid.org/0000-0002-4189-021X18,
* Lan Luong19,
* Xuan Nguyen19 &
* …
* Nathan Congdon ORCID: orcid.org/0000-0001-9866-34161,20,21

Show authors

Trials volume 25, Article number: 825 (2024) Cite this article

* 33 Accesses

* Metrics details

ABSTRACT

BACKGROUND

Traffic crashes are the leading cause of death globally for people aged
5–29 years, with 90% of mortality occurring in low- and middle-income countries
(LMICs). The STABLE (Slashing Two-wheeled Accidents by Leveraging Eyecare) trial
was designed to determine whether providing spectacles could reduce risk among
young myopic motorcycle users in Vietnam.

METHODS

This investigator-masked, stepped-wedge, cluster randomised naturalistic driving
trial will recruit 625 students aged 18–23 years, driving ≥ 50 km/week,
with ≥ 1-year driving experience and using motorcycles as their primary means of
transport, in 25 clusters of 25 students in Ho Chi Minh City, Vietnam.
Motorcycles of consenting students who have failed self-testing on the WHOeyes
app will be fitted with Data Acquisition Systems (DAS) with video cameras and
accelerometers. Video clips (± 30 s) of events flagged by the accelerometer will
be reviewed for crash and near-crash events per 1000 km driven (main outcome).
Five clusters of 25 students will be randomly selected every 12 weeks to undergo
ocular examination and an estimated 40% of these will have bilateral spherical
equivalent < − 0.5 D, and better-eye presenting distance visual acuity < 6/12,
correctable bilaterally to ≥ 6/7.5. They will be given free distance spectacles
and their driving data before receiving spectacles will be analysed as the
control condition and subsequent data as the intervention condition. Secondary
outcomes include visual function, cost-effectiveness and self-reported crash
events.

DISCUSSION

STABLE will be the first randomised trial of vision interventions and driving
safety in a LMIC.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05466955. Initial registration: 20 July 2022, most recent
update: 9 July 2024.

Peer Review reports

INTRODUCTION

Road traffic crashes are the leading cause of death globally among people aged 5
to 29 years and are predicted to become the seventh most-common cause of all-age
mortality by 2030 [1, 2]. Though only 60% of the world’s cars are driven in low-
and middle-income countries (LMICs), 90% of traffic crash mortality occurs there
[1]. Southeast Asia trails only Africa as the global region with the highest
burden of traffic mortality, with 20.7 fatalities per 100,000 population [3].
Drivers aged < 25 years are 15 to 33 times more likely to crash than older
drivers [4]. More than 80% of Vietnamese households own at least one motorcycle,
which comprise 93% of registered motor vehicles in the country [5]. Southeast
Asia is the global region with the highest number of deaths associated with
motorcycle use, accounting for 43% of global fatalities, with Vietnam, where
motorcycles are involved in over two-thirds of road fatalities, having one of
the region’s highest rates of motorcycle-related mortality [3].

Myopic refractive error is the leading cause of distance vision impairment
globally and is steadily increasing [6]. Southeast Asia has the highest
prevalence of adult myopia (32.9%) of any World Health Organisation (WHO)
sub-region [7]. It is estimated that half the world’s population will have
myopia by 2050 [8,9,10]. Uncorrected myopia among young adults in Vietnam, the
age group at greatest risk for road traffic death, accounts for 93% of all
vision impairment [11, 12]. Although myopia can be safely, effectively and
inexpensively treated with spectacles, rates of spectacle ownership among young
people who need them are as low as 15–20% in low- and middle-income countries
(LMICs) [13, 14].

Good vision is widely perceived to be essential for safe driving, as reflected
in motor vehicle licensure laws that require distance vision of a certain
standard before receiving a driver’s licence in many countries. However, there
is little evidence from existing interventional studies that improving vision
enhances traffic safety. Systematic reviews based primarily on studies from
high-income countries have largely failed to detect a strong association between
central vision and crash risk [15]. However, the situation appears to be
different in LMICs. A recent meta-analysis by Piyasena et al. of 13 studies from
LMICs revealed a 46% increased risk of road traffic crashes among drivers with
impaired central visual acuity (risk ratio [RR] 1.46, 95% confidence interval
(CI) 1.20 to 1.78, p < 0.001) and a high prevalence of poor vision among drivers
in such settings [16]. Although some studies have investigated the impact of
vision correction on driving performance [17,18,19], the review by Piyasena et
al. found no randomised trials of vision and driving safety in LMICs [16].

The STABLE (Slashing Two-wheeled Accidents by Leveraging Eyecare) randomised
trial was designed in collaboration with the Vietnamese Ministry of
Transportation to address these evidence gaps by assessing the hypothesis that
the provision of spectacles to young myopic motorcycles drivers in Vietnam can
reduce the rate of crash and near-crash (CNC) events, as measured by on-board
Data Acquisition Systems (DAS) under conditions of naturalistic driving.

MATERIALS AND METHODS

STABLE is an investigator-masked, parallel-group, naturalistic driving study
using a superiority, stepped-wedge, cluster randomised trial (SW-CRT) design,
with faculties within participating universities as the clusters.

STUDY DESIGN

STABLE was designed as a SW-CRT because of the ethical concerns inherent in
failing to deliver spectacles immediately to persons identified with uncorrected
myopia and engaged in a potentially dangerous activity such as driving a
motorcycle, as would occur in a traditional trial. The stepped-wedge design
involves the sequential transition of clusters from control to intervention
conditions in randomised order at 12-week intervals, with spectacles delivered
to those needing them as soon as uncorrected myopia is detected. After all
participant clusters have undergone vision testing and refraction, all eligible
participants will have been exposed to the intervention. This approach balances
the ethical requirement to avoid withholding treatment from known myopic drivers
and the need to conduct a randomised evaluation of the intervention.

PARTICIPANTS AND RECRUITMENT PROCEDURE

The research team will formally engage with the Board of Executives of selected
universities in Ho Chi Minh City, explaining the study’s objectives and
extending invitations for their participation. The study will be advertised via
posters, email and the fan pages of either the Department of Student Affairs or
the Student Union at each enrolled university. To encourage recruitment,
advertisements for STABLE will include a brief description of the incentives for
participation (VND 220,000 or approximately US$9 per student per month for the
duration of involvement in the study) and free spectacles for participants
identified with uncorrected myopia (see below).

Prior to recruitment, potential student participants will be asked to conduct a
smartphone-based vision self-assessment using WHOeyes, the WHO’s free smartphone
application for vision monitoring available in Vietnamese [20, 21]. Those
failing that assessment (an estimated 40% based on pilot testing who have
distance visual acuity in either eye < 6/12, with normal near visual acuity in
both eyes) are at increased risk of refractive error and will be invited to join
the pre-evaluation phase of the study. Students providing informed consent and
meeting the initial inclusion criteria below on a brief survey will have DAS
devices fitted to their motorcycles. These instruments are equipped with front
and rear, driver-facing video cameras and accelerometers, and can detect changes
in speed and direction (such as swerving).

* Enrolled in one of the selected faculties of a participating university

* Aged 18 to 23 years

* Sole driver of their motorcycle

* Use their motorcycle as their primary means of transport

* Drive ≥ 25 km/week by self-report

* Hold a valid driving licence if required (for motorcycles having an engine
capacity > 50 cc)

* Failed the WHOeyes vision self-assessment in at least one eye

As shown in Fig. 1, all potential participants enter in the control condition
and will have DAS units installed on their motorcycles. However, as they have
not yet been examined and refracted, the identity of actual trial participants
is not known at that time. Subsequently, during the 14 days before each 12-week
period, participants in five randomly selected clusters will undergo an eye
examination and refraction. Those meeting the following criteria will receive
spectacles within 1 week of the examination and transition to the intervention
condition, and their previously collected DAS information will be analysed as
control data:

* Presenting distance visual acuity < 6/12 in the better-seeing eye due to un-
or under-corrected myopia

* Vision correctable with glasses to 6/7.5 or better in both eyes

* At least 0.5 D of myopia in both eyes

Fig. 1

Schematic diagram of participant recruitment and allocation in the STABLE trial

Full size image

Participants who do not meet the above inclusion criteria will have DAS units
removed from their motorcycles, never having entered the trial itself, and the
data collected previously will not be used in the STABLE analyses.

STUDY INTERVENTION

Over the 72 weeks of the study, an estimated 250 students from the 25 clusters,
randomised in groups of five clusters, will enter the intervention condition.
Each of these participants will receive a free pair of spectacles with
spherocylindrical power in each eye as measured during refraction by an
optometrist. Refractive power will be based on non-cycloplegic automated
refraction (QuickSee, Plenoptika, Cambridge, USA) and subjective refinement.
Spectacle-wear compliance will be assessed and recorded throughout the trial
based on footage from the driver-facing cameras. Replacement spectacles will be
provided free of charge as needed due to loss or breakage. Research staff will
communicate with trial participants observed having poor compliance in order to
improve their use of the spectacles. Myopia progression in this age group is not
expected to be clinically meaningful over the 72 weeks, so there are no
provisions for routine re-evaluation of refractive power. However, participants
complaining of declining vision or symptoms associated with spectacle wear will
be examined at study clinics, with replacement spectacles provided as needed.

OUTCOME MEASURES

PRIMARY OUTCOME

The primary trial outcome is the number of CNC events per 1000 km driven. Study
participants will be asked to meet with research staff every 2 weeks to exchange
the USB drives from their DAS units for empty drives. Potential CNC events will
be extracted from the DAS recordings using mining algorithms in which kinematic
data (lateral and longitudinal acceleration due to hard braking events or the
vehicle having fallen on its side) will be passed through filters to discover
points at which a CNC event may have occurred. Personnel trained in video
reduction will then examine the video footage of the candidate CNC event to
assess the content, nature and severity.

An analysis of the probability of CNC events will require the collection and
analysis of data from periods (epochs) of motorcycle use free from CNC events.
The number of baseline epochs collected for each motorcycle driver will be
calculated as a percentage of the total number of kilometres travelled by all
drivers during the course of the study. The start-point for each baseline epoch
will be randomly selected from the drivers’ video data. If the motorcycle is
moving more than 5 km/h, 10 s of video data will be extracted and analysed by
video reduction personnel who will record roadway (road type and condition) and
traffic variables; riding behaviour (overtaking, speed); riding manoeuvres
(turning or going straight, etc.); presence of passengers and environmental
conditions (e.g. weather conditions) for each baseline epoch interrogated.
Assessors will be masked to the participant’s allocation.

SECONDARY OUTCOMES

Secondary outcomes include self-reported visual function (driving-adapted Visual
Function Questionnare-25 [VFQ-25]) [22] administered at baseline and 1 month
after receiving spectacles; self-reported crashes and injuries reported every
2 weeks by questionnaire (Crash and Injury Self-Report Questionnaire [CI SRQ]);
self-reported crashes (compared with DAS-recorded crashes); and total delivery
cost per CNC event avoided in the intervention condition (as an indicator of
cost-effectiveness).

SAMPLE SIZE

Unpublished data from Dynamic Vision, an organisation currently collecting CNC
events from motorcycle drivers in Vietnam, were used to inform the power
calculation. Results showed an estimated mean event rate of 1.67 CNC events per
1000 km driven (standard deviation [SD] = 0.556). For a postulated, clinically
meaningful 10% reduction in CNC events, a stepped-wedge cohort design comprising
six sequences of seven myopic participants per cluster (a 28% prevalence, below
the 40% figure observed during pilot testing with the WHOeyes app), a
coefficient of variation of cluster sizes of 3, and five clusters per sequence
with Individual Auto Correlation (IAC) of zero, confer 90% power (mean
difference = 0.167, SD = 0.556; intraclass correlation [ICC] = 0.02 [0.01–0.05])
[23]. This would be achieved by collecting DAS data from 175 students over the
course of 72 weeks. To achieve this, 5200 students will be invited to
self-assess their vision using WHOeyes. Pilot data indicate that approximately
12%, or 625 students, will fail that assessment and be eligible to join the
preliminary phase of the study, with placement of DAS units on their
motorcycles. An estimated 250 (40% of those failing the WHOeyes self-assessment)
will have eligible, uncorrected/under-corrected myopia detected on their
subsequent eye examination by an optometrist. They will then be assigned to the
intervention condition and given free spectacles. With a 30% dropout rate, this
will result in complete datasets for 175 participants over the course of the
trial.

RANDOMISATION, ALLOCATION AND CONCEALMENT

The random selection of clusters will occur 3 weeks prior to the scheduled date
for eye examinations. The identity of the selected five clusters will not be
known by the investigators or anyone involved in the trial before randomisation.

The Northern Ireland Clinical Trials Unit (NICTU) will use a centralised system
to manage the randomisation process in collaboration with the LV Prasad Eye
Institute Clinical Trials Unit (LVPEI CTU). The NICTU will advise LVPEI CTU of
the clusters selected 5 weeks before the transition date. Then, LVPEI CTU will
inform the site principal investigator or an individual with delegated authority
of the five clusters selected. The 125 participants in these randomly selected
clusters (25 participants per cluster) will then be notified of the eye
examination and reminded 14 days, 5 days and 1 day in advance.

REPORTING OF ADVERSE EVENTS

The period for reporting adverse events (AE) in the trial commences when
informed consent is received from a participant and terminates when the DAS unit
is removed from his/her motorcycle. AEs will be recorded and reported in
compliance with Vietnamese national guidelines. Any serious adverse events
(SAEs) will be promptly reported using the designated form. The LVPEI CTU will
be notified of all SAEs by email within 24 h and will notify the chief
investigator and sponsor of all SAEs within an additional 24 h. The LVPEI CTU
will notify the Queen’s University Belfast (QUB) Research Ethics Committee of
all SAEs within 7 days. The local principal investigator will provide annual
progress reports to the local IRB.

ADDITIONAL DATA COLLECTION

The following information will be collected by questionnaire from those who fail
the WHOeyes self-assessment in at least one eye: age, driving experience,
primary means of transport, distance driven per week, motorcycle type, brand,
model and engine capacity, and possession of a driving licence. Those meeting
the inclusion criteria for DAS fitting and providing informed consent will be
asked to provide the following baseline data: exposure to eyecare assessments at
time of licensure, visual function (VFQ-25) [22], driver risk profile (Dula
Dangerous Driving Index [DDDI]) [24] and economic data including home location
(urban or rural), income and estimated monthly expenditures. At the time of the
eye examination but before the participant’s cluster transitions to the
intervention condition, data will be collected on visual acuity, refractive
error, details of current spectacle wear, presence of ocular abnormalities and
whether spectacles are required. Data will subsequently be collected on whether
spectacles are provided.

Every 2 weeks, participants meeting with study staff to exchange the removable
drive in their DAS units will be asked whether they have been involved in a
crash in the preceding 2 weeks. Repair and insurance costs will be recorded if a
crash occurs. Financial data for the cost-effectiveness calculations from a
societal perspective will be captured, including cost of health care received
and for crash-related repairs.

DATA MANAGEMENT

Data from each participant in the preliminary study phase and/or the trial will
be recorded in the study database by Asia Injury Prevention Foundation (AIPF)
staff. Standard validation procedures will be implemented to ensure consistency,
reliability and full compliance with Good Clinical Practice (GCP) [25] and other
pertinent regulatory requirements. The database with CNC and compliance
information will be under the custodianship of University of Medicine and
Pharmacy (UMP). NICTU’s standard procedures for data backup, storage and
security will be strictly followed for data entered into the trial management
software. Access to these data will be restricted to authorised personnel.

STATISTICAL ANALYSES

All outcomes for trial participants will be analysed in accordance with the
intention-to-treat (ITT) principle. Baseline characteristics will be summarised
using means and standard deviations, medians and interquartile ranges, or
numbers and percentages, as appropriate. The primary outcome (number of CNC
events per 1000 km driven) will be analysed using generalised linear mixed
models, reporting mean differences and adjusting for cluster, secular and time
effects. For example, secular trend adjustments will take into consideration
national and regional driving safety campaigns and calendar time. Seasonal
factors (amount of daylight, inclement weather, etc.) are likely to play a role
in the number and severity of CNC events. Analysis of secondary outcomes will be
done in a similar fashion. Risk differences for binary outcomes and mean
differences for continuous outcomes, all adjusting for cluster, secular and time
effects, will be reported.

Sensitivity analyses will be conducted to examine the intervention effects,
adjusting for additional pre-specified potential confounders including age
(years as a continuous variable), DDDI risk profile [24] (total score as a
continuous variable) and residence (rural/urban as a binary variable).

Missing data will likely result when participants withdraw from the study or do
not complete the full follow-up. Multiple imputations of missing data when
assessing secondary outcomes will involve creating 20 copies of the data and
imputing missing values by chained equations before averaging the datasets [26].

TRIAL MONITORING

The trial will be independently monitored by a Data Monitoring and Ethics
Committee (DMEC), with the remit to protect and serve study participants,
especially regarding safety, and to assist and advise the chief investigator to
protect the validity and credibility of the trial. No interim analyses of the
trial outcomes are planned.

PROTOCOL COMPLIANCE

A protocol deviation is defined as a failure to adhere to the protocol, such as
delivering an incorrect intervention or errors in applying eligibility criteria.
Major protocol deviations constitute instances where enrolled participants have
not provided informed consent or deliberately provide incorrect data. Other
protocol deviations include situations where participants are incorrectly
randomised, or where participants in the intervention condition have not receive
the prescribed spectacles.

PARTICIPANT CONFIDENTIALITY

The chief investigator and local principal investigator are responsible for
assuring participant privacy. All participant information and records in the
study will be pseudo-anonymised with an identification code. Electronic and
paper-based data that could reveal a participant’s identity will be securely
stored on a server with access limited to designated study personnel, or in
locked filing cabinets at UMP until data collection is completed. Anonymised
data will be retained for 10 years in accordance with the funder’s requirements
(https://www.ukri.org/wp-content/uploads/2020/10/UKRI-020920-ConcordatonOpenResearchData.pdf)
and then treated as confidential waste and destroyed.

DISCUSSION

Road traffic crashes are the leading cause of mortality among people aged
5–29 years, and 90% of this burden falls on LMICs [1]. Poor vision due to
uncorrected refractive error in Vietnam and Southeast Asia, especially among
young people [7, 11, 12], has been shown in a recent meta-analysis to increase
the risk of road crashes by 46% [15]. Despite evidence of the link between good
vision and road safety, there are few studies on interventions to reduce crash
risk by treating vision disorders such as myopia [17,18,19]. The recent
meta-analysis and review by Piyasena et al. found no randomised trials on vision
care and traffic safety in LMICs [16]. The STABLE trial will help to fill this
knowledge gap by examining the effects of spectacles to correct myopia to reduce
crashes among university students in Vietnam. It will be the first randomised
trial of vision interventions and driving safety in a LMIC and a successful
trial outcome will help to inform strategies to reduce traffic crashes in the
future through wide dissemination and engagement with policy makers.

TRIAL STATUS

This paper is based on version 4.2 of the STABLE protocol (dated 15 May 2024).
Important changes to the protocol will be communicated to the relevant ethics
committees and trial registries as needed. Recruitment to STABLE is expected to
start and be completed (given the stepped-wedge design which requires all
participants to be included at the outset) in the fourth quarter of 2024.

DATA AVAILABILITY

Following publication of the results for the primary and secondary outcomes,
there may be scope for supplementary analyses by third parties on the data
collected. In such cases, written formal requests to access the data must be
sent to the chief investigator through the NICTU for discussion with the
sponsor. The study will comply with good practice principles for sharing
individual participant data from publicly funded clinical trials [27, 28]. Data
sharing will be undertaken in accordance with the required regulatory
requirements. In the event of publications arising from these analyses, those
responsible will provide the chief investigator with a copy of the intended
manuscript for approval before submission and acknowledge the source of the data
they use. No identifying images or other personal or clinical details of
participants are presented here or will be presented in reports of the trial
results. The participant information materials and informed consent form are
available from the corresponding author on request.

ABBREVIATIONS

LMICs:

Low- and middle-income countries

STABLE:

Slashing Two-wheeled Accidents by Leveraging Eyecare

DAS:

Data Acquisition Systems

CNC:

Crash-near crash

WHO:

World Health Organisation

SW-CRT:

Stepped-wedge, cluster randomised trial

VFQ-25:

Visual Function Questionnare-25

CI SRQ:

Crash and Injury Self-Report Questionnaire

IAC:

Individual Auto Correlation

ICC:

Intraclass correlation

QUB:

Queen’s University Belfast

NICTU:

Northern Ireland Clinical Trials Unit

LVPEI CTU:

LV Prasad Eye Institute Clinical Trials Unit

AE:

Adverse events

SAEs:

Serious adverse events

AIPF:

Asia Injury Prevention Foundation

GCP:

Good Clinical Practice

DDDI:

Dula Dangerous Driving Index

ITT:

Intention-to-treat

UMP:

University of Medicine and Pharmacy

DMEC:

Data Monitoring and Ethics Committee

ICH:

International Conference on Harmonisation

ENGINE:

Eyecare Nurtures Good-health, Innovation, driviNg-safety and Education

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ACKNOWLEDGEMENTS

We thank the independent members of the Trial Steering Committee (Le Thi Kim
Anh, VoThi Bao Chau, Pham Viet Cuong, Nguyen Thi Thuy Dung, Tang Kim Hong, Lisa
Keay, Mark King and Paul Roberts) and the Data Monitoring and Ethics Committee
(Neelum T Aggarwal, Kavi Bhalla, Catey Bunce, Andrew Copas, Tianjing Li, Aletta
Nonyane, Ravi Parikh and Sanjay Rampal) for STABLE. The trial sponsor is Queen’s
University Belfast, Northern Ireland. More details on the trial are available at
https://www.qub.ac.uk/sites/engine-vision/.

AUTHORSHIP ELIGIBILITY GUIDELINES, USE OF PROFESSIONAL WRITERS

To be considered eligible for authorship status, collaborators had to have
played a material role in study design, data collection/analysis and/or
writing/review of the manuscript. No professional writers were involved in
composition of the manuscript.

FUNDING

The STABLE trial is funded by the Wellcome Trust Investigator Award in Science
application as part of the broader ENGINE (Eyecare Nurtures Good-health,
Innovation, driviNg-safety and Education) project (Nathan Congdon and Rohit
Khanna, ref: 222490/Z/21/Z) and Chen Yet-Sen Family Foundation (Special Projects
ref: 222490/Z/21/Z). The funders have no role in decisions about submission of
trial manuscripts, including this protocol.

AUTHOR INFORMATION

AUTHORS AND AFFILIATIONS

1. Centre for Public Health, School of Medicine Dentistry and Biomedical
Sciences, Queen’s University Belfast, Belfast, BT12 6BA, UK

Vinh Chi Le, Ving Fai Chan, Mike Clarke, Lynne Lohfeld, Augusto
Azuara-Blanco & Nathan Congdon

2. Faculty of Public Health, University of Medicine and Pharmacy at Ho Chi
Minh City, 217 Hong Bang Street, District 5, Ho Chi Minh City, Vietnam

Vinh Chi Le, Kien Gia To, Han Thi Ngoc Doan, Dung Van Do & Phuoc Hong Le

3. Transport Development and Strategy Institute, Hanoi, Vietnam

Van Dat Le

4. Asia Injury Prevention Foundation, Hanoi, Vietnam

Le Nguyen & Mai Tran

5. Riemann Limited, London, UK

Graeme MacKenzie

6. Hyderabad Eye Research Foundation, L V Prasad Eye Institute, Hyderabad,
Telangana, India

Lovemore Nyasha Sigwadhi, Rohit C. Khanna, Asha Latha Mettla, Sridevi
Rayasam & Raja Narayanan

7. Vision and Eye Research Institute, Anglia Ruskin University, Cambridge, UK

Prabhath Piyasena

8. Allen Foster Community Eye Health Research Centre, Gullapalli Pratibha Rao
International Centre for Advancement of Rural Eye Care, L V Prasad Eye
Institute, Hyderabad, India

Rohit C. Khanna

9. Brien Holden Eye Research Centre, L.V. Prasad Eye Institute, Banjara Hills,
Hyderabad, India

Rohit C. Khanna

10. School of Optometry and Vision Science, University of New South Wales,
Sydney, Australia

Rohit C. Khanna

11. School of Medicine and Dentistry, University of Rochester, Rochester, NY,
USA

Rohit C. Khanna

12. Northern Ireland Clinical Trials Unit, Belfast, UK

Mike Clarke, Lynn Murphy, Joanne Thompson, Susan McMullan & Cliona McDowell

13. Centre for Health Research at the Management School Economics, Queen’s
University Belfast, Belfast, UK

Heather Dickey

14. Virginia Tech Transportation Institute, Blacksburg, USA

Charlie Klauer, Richard Hanowski & Zeb Bowden

15. Centre of Optometry and Vision Science, School of Biomedical Sciences,
Ulster University, Coleraine, UK

Julie-Anne Little

16. Hanoi Medical University, Hanoi, Vietnam

Huong Thu Ha

17. Department of Medical Humanities and Social Sciences, Yonsei University
College of Medicine, Seoul, Republic of Korea

Sangchul Yoon

18. Transportation Research and Injury Prevention Centre, Indian Institute of
Technology, Delhi, New Delhi, India

Rahul Goel

19. Eye Care Foundation, Ho Chi Minh, Vietnam

Lan Luong & Xuan Nguyen

20. Department of Preventive Ophthalmology, Zhongshan Ophthalmic Center,
Guangzhou, Guangdong, China

Nathan Congdon

21. Orbis International, New York, USA

Nathan Congdon

Authors
1. Vinh Chi Le
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