DigiVis: Self-testing Vision App for Telephone Consultations

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 Cambridge
University Hospitals NHS Trust (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.
The investigators 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.

The investigators wish to formally validate DigiVis home testing following Conformitè
Europëenne (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.