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.
This trial aims to assess the accuracy and test-retest variability of a new digital app which enables community visual acuity testing without requirement of an trained examiner.