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Vision test validation: the Peek Acuity app

Research briefing:
Peek Acuity, our smartphone-based distance vision check app, is as accurate as traditional charts.



Peek Acuity is an app available on Android phones, used to determine how clearly an individual sees objects at a distance. The app vision test is designed not to be dependent on familiarity with symbols or letters used in the English language. It features a “tumbling E” on screen, showing the letter E displayed in 1 of 4 orientations. The participant points in the direction they perceive the arms of the E to be pointing. The tester uses the touch screen to swipe accordingly, translating the gestures from the patient to the phone, as the image gets smaller. This study compared Peek Acuity to standard paper-based charts and illuminated vision boxes used to test vision in an eye clinic. Tests (using Peek Acuity at a distance of 2m and a reduced 3m “tumbling E” Snellen chart) were carried out in the participant’s home and in a clinic on two consecutive days.

What did the research show?

  • Results from the app tests carried out on 233 people in their own homes and repeated in eye clinics based in Kenya were as reliable as those from standard paper-based charts and illuminated vision boxes in an eye clinic.
  • Tests in patients’ homes found that Peek Acuity produced results to a clinical level equivalent to the much larger and more expensive standard electricity-dependent chart – the average difference being the equivalent of less than one line on an eye chart.
  • Average testing time was also measured and found that the familiar and commonly-used Snellen test took 82 seconds compared with 77 seconds for Peek Acuity which shows that using Peek is as quick to use as traditional methods.

In this study we aimed to develop and validate a smartphone-based visual acuity test for eyesight which would provide reliable results and work in challenging circumstances, such as rural Africa. Our ultimate hope is that the accuracy and easy to use features of Peek will lead to more people receiving timely and appropriate treatment and be given the chance to see clearly again.”

Andrew Bastawrous
Study lead author and Co-Founder of Peek Vision.


  • Peek Vision
  • International Centre for Eye Health at the London School of Hygiene & Tropical Medicine
  • Kitale Hospital, Kenya


The Peek validation research took place as part of the Nakuru Eye Disease Cohort Study, which was funded by the Medical Research Council and the Department for International Development, and Fight for Sight. Additional funding to support the Peek study was provided by the International Glaucoma Association and the British Council for the Prevention of Blindness. Funding for other Peek trials was provided by The Queen Elizabeth Diamond Jubilee Trust.