DigiVis: Validation of Self-testing Visual Acuity Web-based App to Aid Ophthalmic Telephone Consultations During Covid19 Lockdown and Subsequent Social Distancing Crisis
Phase: NA
Conditions: Visual Impairment, Amblyopia Suspect
Sponsor: Cambridge University Hospitals NHS Foundation Trust

  
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DigiVis: validation of self-testing visual acuity web-based app to aid ophthalmic 
telephone consultations during Covid19 lockdown and subsequent social distancing 
crisis. 
 
Clinical Study Protocol 
 
 
Protocol Number: 
DigiVis v0.1  
 
NCT:  
 
IRAS ID 196573 
Document date: 
15th July 2020  
 
 
 
Study Title: 
DigiVis: validation of self-testing visual acuity web-based app 
to aid ophthalmic telephone consultations during Covid19 
lockdown and subsequent social distancing crisis.  
Investigational Product: Web-based Visual Acuity software  
Protocol Version: 
Version 0.1    
 
 
Chief investigator: 
Miss Louise E Allen MBBS MD MA FRCOphth 
 
Consultant Paediatric Ophthalmologist, Addenbrooke’s 
Hospital 
 
Investigator’s address: 
Box 41, Ophthalmology Department 
 
Hills Road 
 
Cambridge 
 
CB2 0QQ 
Study Location: 
Addenbrooke’s Hospital, Cambridge (CUHFT)  
Telephone: 
01223 216700 
 
Study Sponsor: 
Cambridge University Hospitals NHS Foundation Trust  
 
 
 
 
 

  
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1 Study Synopsis 
Title of clinical trial 
DigiVis: self-testing vision app for telephone 
consultations 
Sponsor name 
Cambridge University Hospitals NHS Trust 
Medical condition under investigation 
Visual Acuity (VA) assessment  
Purpose of clinical trial 
To validate VA self-assessment using DigiVis 
software by comparison to current chart-based tests 
Primary objective 
Comparison of VA assessment with DigiVis software 
to clinic-based VA assessment. 
Secondary objective (s) 
Calculation of test-retest variability. 
Assessment of usability and preference. 
Study Design  
Prospective quantifiable comparison study  
Study Endpoints 
Completed testing on a sufficient number of 
individuals to give good statistical power. 
Sample Size 
Approximately 250 patients in total  
Summary of eligibility criteria 
Patients aged between 5 and 85 due to attend 
scheduled clinic appointment with vision 
+0.8logMAR (6/38) or better in their left eye.  
Patients with access to two appropriate digital 
devices. 
Ability to understand English and log on to the 
website. 
Active comparator product(s) 
Clinic VA charts: LogMAR visual acuity chart, SLT 
childrens’ vision chart. 
Route(s) of administration  
Visual test 
Maximum duration of treatment  
2 clinical interventions of 5 minutes each at home 
Procedures: Screening & enrolment 
Eligible patients will be identified from electronic 
patient record prior to a scheduled clinical 
appointment.  
Telephone enrolment will be undertaken.  
 
Comparators 
VA test at the scheduled clinic appointment.  
Two DigiVis self-test VA measurements. 
Patient preference.  
 
Intervention period 
Two 10 minute phone calls explaining study and the 
test 
Two 5 minute self-tests of VA on the website 
10 minutes conversation to sign the consent form in 
clinic and get usability feedback 
 
End of Study 
End of scheduled clinic appointment 
Procedures for safety monitoring during 
trial 
n/a  
Criteria for withdrawal of patients on 
safety grounds 
n/a 
Regulatory submissions on safety grounds 
Software marked as CE Class I Medical Device 

  
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2 Introduction 
2.1 Background 
 
Eye problems like macular degeneration and amblyopia (lazy eye) require regular 
monitoring to prevent permanent visual impairment. Over 2000 patients a month are 
seen in CUH eye clinics; concern about Covid-19 infection has led to over 80% of 
consultations being conducted by telephone with few clinical clues to inform decision 
making. Patients will face long delays even when routine clinics restart: there is no 
doubt that some will suffer preventable visual loss.  
DigiVis is a web-based vision testing app enabling self-testing of vision at home. Early 
testing and patient feedback is positive: 80% of children prefer DigiVis to regular testing. 
We wish to test how accurately the app works for home use, by asking older children 
and adults to self-test their vision prior to their planned face to face clinic appointment.  
Once tested, DigiVis will be available free of charge to patients, not only during the 
Covid-19 crisis, but also to support telephonic consultations in the future. 
 
Visual acuity (VA) is a fundamental measure of vision required for all ophthalmic 
assessments. It is measured by health professionals using vision charts. DigiVis is a new 
app which enables self-testing of VA using two wirelessly connected digital devices. By 
matching letters on a handheld device to those displayed on the second device a 
distance away, threshold VA can be measured using a staircase algorithm. The distance 
and scaling of the test is vital to its accuracy and a concept (patent filed by Cambridge 
Enterprise) in DigiVis enables this without the need for manual distance measurement 
or an observer.  
Early validation using two tablet computers in 150 clinic patients has given positive 
results, both in testing accuracy and patient feedback. With the current Covid-19 crisis 
limiting face to face appointments, there is an urgent need for accurate home VA 
assessment. The DigiVis app has been re-coded for free website delivery for this 
purpose.  
We wish to formally validate DigiVis home testing following CE (class I) marking so that it 
can be recommended for clinical use. 250 patients will be invited to self-test their VA 
twice using DigiVis prior to a planned face to face clinic appointment. The test-retest 
variability and comparison of DigiVis VA to chart based assessment will be compared.  
 
The DigiVis test can be undertaken at www.digivis.org with a code name of louiseallen. 
 
2.2 Data from other studies 
 
The DigiVis software app has already undergone initial validation and usability studies in 
clinic patients, which have resulted in software improvement including a reduction of 
test time.  
 

  
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A similar study design has been used to assess Peek vision, a smartphone based VA 
testing app. (1) The difference between DigiVis and Peek app is the automated distance 
measurement, no requirement for an observer and use of standardised optotype design 
in the former. 
 
2.3 Safety data 
The software is CE marked Class1 medical devices and is delivered on a web-site 
accessed from the patients’ own digital devices, no safety issues are foreseen.  
3 Rationale for Study 
Validation of the accuracy of the software package will enable recommendation of its 
use in conjunction with telephone consultation to inform clinical decision making during 
and after the lockdown period as social distancing increases the need for virtual 
consultations.  
4 Trial objective and purpose 
Primary objective: to compare VA assessment of self-testing on the DigiVis website to 
formal VA measurement using chart-based tests in clinic.  
Secondary objective: to assess the repeatability and usability of the software.  
4.1 Statement of design 
This is a prospective quantifiable comparison study.   
4.2 Study duration 
Study duration will be 6 months, aiming to start testing by the 3rd June 2020 and 
complete testing by 3rd February 2021. 
4.3 
Study objectives 
4.3.1 
Primary research question 
Is the visual acuity score measured by home self-testing with DigiVis comparable to 
current chart-based clinic methods?  
4.3.2 
Secondary research question 
What is the test-retest variation (repeatability) of the DigiVis system?  
What is the ease of use of the app and what features could be modified to improve 
usability? Study endpoints 
4.3.3 
Primary endpoint 
Clinical testing will cease once at least 250 individuals have been recruited to enable 
adequate statistical power using Bland-Altman calculations.  

  
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4.4 Criteria for Discontinuation 
4.4.1 
Individual subject 
Request of the child or parent to withdraw from study or cease testing. 
 
5 Selection and withdrawal of subjects 
5.1 Inclusion Criteria 
 Age between 5 and 85 years scheduled to have face to face appointment within 
two weeks 
 Previous recorded visual acuity of +0.8logMAR (6/38) or better in the left eye 
5.2 Exclusion Criteria 
 Individuals with poor conversant English  
 Patients with cognitive impairment 
 Patients without suitable digital devices or inability to access the internet 
5.3 Assignment and Randomisation Number 
The data regarding VA assessment of the left eye only of individuals will be analysed. 
5.4 Method of Blinding 
The health care assistant or orthoptist undertaking the standard chart-based test will 
not have knowledge of the DigiVis VA results.  
5.5 Emergency Unblinding 
Not applicable 
5.6 Subject withdrawal criteria 
The individual will be withdrawn from the study if it he/she is unable to access the 
DigiVis website or undertake the test twice.  
6 Study procedure and assessments 
6.1 Informed consent 
Subjects who fulfil the inclusion criteria will undergo the following consent process: 
 
First telephone call: 
The researcher will telephone patients prior to their scheduled face to face clinic 
appointment for an introductory phone call to explain the study and to determine if any 
exclusion criteria apply. 
 
If interested in the study at this first contact, the individual will be directed to the 
website and shown how to access the study information and consent form. The 
researcher will go over both forms with the potential participant. A convenient time for 
a follow up call at least 30 minutes after the first will be arranged to allow the patients 

  
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to consider participation and discuss with friends and family. They will be informed that 
non-participation will not affect patient care. Access to the website is possible via a 
password and no personal information is stored in the web-server.  
 
Second telephone call: 
If the patient wishes to participate in the study they will be asked to read and 
electronically consent to undertaking the DigiVis test on the website itself. The 
researcher will then help them undertake the first VA test and will note down the VA 
values. The participant will be asked to undertake the test themselves a second time 
before their scheduled clinic appointment and note down, or take a photo of, their VA 
score.  
 
Clinic assessment: 
At this appointment, as standard practice, chart-based VA will be assessed by a health 
care professional (who is masked to the result of the DigiVis scores). A researcher will 
approach the subject during their visits and the formal study consent form will be signed 
and the usability feed-back documented. 
6.2 Personal data 
The personal data recorded for the study will be hospital number and date of birth.  
Study data will include: DigiVis VA score x 2, chart based VA score, usability score and 
patient comments. 
 
7 Evaluation of Results  
Bland Altman statistical methods and calculation of test-retest variability will be 
calculated after 100 adults and 150 children have been tested.  
8 Assessment of Safety  
No safety issues are expected during this study because the patients is using their own 
devices and the clinic element of the study is standard clinical practice. 
9 Statistics 
9.1 Statistical methods to be employed 
Bland-Altman statistics similar to those illustrated in the initial validation studies will be 
used. In addition test-retest variability and quantative comparison of preference and 
usability will be analysed. Sample size requirements have been calculated using MedCalc 
based on the results from the initial validation studies (graph 1&2) 
9.2 Number of Subjects to be enrolled 
100 adults 
150 children aged 5-16years 
9.3 Criteria for the termination of the trial 
Website issues, although this is unlikely since the website is already running and tested. 

  
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9.4 Procedure to account for missing or spurious data 
The first DigiVis score will be take down over the telephone at the time of the second 
call. It is possible that the participant may forget to take the DigiVis a second time or 
forget to bring the VA score. Where this occurs, the DigiVis test will be repeated in clinic.   
9.5 Definition of the end of the trial  
Interim data analysis will be undertaken once 100 adults and 150 children have been 
tested to ensure sufficient statistical power. If insufficient further recruitment may be 
necessary. 
10 Direct access to source data / documents 
The investigators will permit trial related monitoring, audits, REC review, regulatory 
inspections. 
11 Ethical considerations – none forseen 
11.1 Consent 
All patients will freely give their informed consent to participate in the study. A patient 
may decide to withdraw from the study at any time without prejudice to their future 
care. 
Initial electronic consent will be given by parents at the time of their DigiVis testing. 
Formal written consent will be collected at the time of their clinic attendance.  
11.2 Ethical committee review 
The study protocol will be submitted to the appropriate ethical review committee with a 
letters of approval filed in the study file 
11.3 Declaration of Helsinki and ICH Good Clinical Practise 
The study will be carried out in conformation with the spirit and the letter of the 
declaration of Helsinki, and in accord with the ICH Good Clinical Practice Guidelines  
12 Data handling and record keeping 
Data with personal information will be kept for analysis 6-12 months following study and 
subsequently pseudonymised and kept as a file on an NHS hospital computer for a 
period of 15 years by Miss Allen. 
13 Financial and Insurance  
This trial has been funded by a combination of Addenbrooke’s Charitable Trust and Fight 
Against Blindness charitable funding. The original coding of DigiVis was enabled by an 
MRC: Confidence in concepts grant in 2016. The investigators will be working within 
Cambridge University Hospitals NHS Trust and will be indemnified by the NHS. 
The VA app will be available free of charge to patients for the foreseeable future. 

  
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14 Publications policy 
Publications arising from the trial will be authored by Miss Allen. If acceptable accuracy 
and reliability of DigiVis self-assessment is demonstrated, it is likely that the app will be 
recommended for the use by the Royal College of Ophthalmologists.  
References 
1) Bastawrous A, Rono H, Livingstone IA, ey al. The development of a smartphone 
visual acuity test (Peek acuity) for clinical practice and community based field 
work. JAMA Ophthalmol. 2015 August;133(8) 930-937