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Validation of electronic visual acuity (EVA) measurement against standardised ETDRS charts in patients with visual field loss from inherited retinal degenerations
  1. Jasleen K Jolly1,2,3,
  2. Kristin Juenemann3,
  3. Heather Boagey1,
  4. Marie Nadsady2,
  5. Holly Bridge3,
  6. Robert E Maclaren1,2
  1. 1 Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
  2. 2 Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
  3. 3 Oxford Centre for Functional MRI of the Brain (FMRIB), Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
  1. Correspondence to Jasleen K Jolly, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX1 2JD, UK; jasleen.jolly{at}


Background With the increase in clinical trials testing therapy for retinal disease, there is a need to ensure that outcome measures are both accurate and standardised. The US Food and Drug Administration favours the use of visual acuity measured using ETDRS logMAR charts. The loss of visual field can interfere with visual tracking across the charts, leading to increased variability of measurements. Electronic visual acuity (EVA) presents the optotype on the centre of a screen, thereby removing the tracking element of the task, and may provide a more precise measurement.

Methods Visual acuity was measured twice using ETDRS charts, EVA automated single letter (E-ETDRS) and EVA single line (EVA-SL) presentation (EMMES). Patients underwent microperimetry (MAIA; Centervue) to determine visual field. We tested 65 patients with rod-cone dystrophies and 41 healthy volunteers.

Results Both participant groups read 2–3 letters more on average on the electronic charts compared with ETDRS. Limits of agreement using a modified Bland-Altman analysis account for replicates were wider in eyes with foveal defects (−9 to 18) compared with eyes without foveal defects (−11 to 15). Electronic charts in the presence of foveal defects reduced the range (−11 to 13).

Conclusion EVA may provide more accurate measures of visual acuity than traditional ETDRS charts in patients when the visual field loss encroached on the central vision. Electronic presentation with a single line of letters was the favoured style reported by patients and should be considered in future interventional clinical trials.

  • field of vision
  • diagnostic tests/investigation
  • degeneration
  • psychophysics
  • VISual perception

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  • Presented at Presented at ARVO 2019.

  • Contributors JKJ designed the study. REM contributed to the concept. JKJ, KJ, HBo and MN collected the data. JKJ, KJ and MN carried out data analysis. HBr and REM provided input on data analysis. JKJ wrote the manuscript. KJ, HBo, MN, HBr and REM provided feedback on the manuscript.

  • Funding This study is funded by the National Institute for Health Research (NIHR) (Clinical Doctoral Research Fellowship CA-CDRF-2016-02-002 for JKJ).

  • Disclaimer The views expressed are those of the authors and not necessarily those of the National Health Service, the NIHR or the Department of Health and Social Care. The sponsor and funding organization had no role in the design or conduct of this research.

  • Competing interests REM receives grant funding from Nightstar Therapeutics. REM is a consultant to Nightstar Therapeutics and Spark Therapeutics. These companies did not have any input into the work presented.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on request.

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