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Laboratory and vision science
Real-world application of a smartphone-based visual acuity test (WHOeyes) with automatic distance calibration
  1. Yi Wu1,
  2. Stuart Keel2,
  3. Vera Lúcia Alves Carneiro2,
  4. Shiran Zhang1,
  5. Wei Wang1,
  6. Chi Liu3,
  7. Xuanzhang Tang1,
  8. Xiaotong Han1,
  9. Mingguang He1,4,5
  1. 1State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
  2. 2Department of Noncommunicable Diseases, Vision and eye care programme, World Health Organisation, Geneva, Switzerland
  3. 3Faculty of Data Science, City University of Macau, Macao SAR, China
  4. 4School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
  5. 5Research Centre for SHARP Vision, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
  1. Correspondence to Prof. Xiaotong Han, State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China; hanxiaotong2{at}gzzoc.com; Prof. Mingguang He, State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China; mingguang_he{at}yahoo.com

Abstract

Background To develop and assess the usability of a smartphone-based visual acuity (VA) test with an automatic distance calibration (ADC) function, the iOS version of WHOeyes.

Methods The WHOeyes was an upgraded version with a distinct feature of ADC of an existing validated VA testing app called V@home. Three groups of Chinese participants with different ages (≤20, 20–40, >40 years) were recruited for distance and near VA testing using both an Early Treatment Diabetic Retinopathy Study (ETDRS) chart and the WHOeyes. The ADC function would determine the testing distance. Infrared rangefinder was used to determine the testing distance for the ETDRS, and actual testing distance for the WHOeyes. A questionnaire-based interview was administered to assess the satisfaction.

Results The actual testing distance determined by the WHOeyes ADC showed an overall good agreement with the desired testing distance in all three age groups (p>0.50). Regarding the distance and near VA testing, the accuracy of WHOeyes was equivalent to ETDRS. The mean difference between the WHOeyes and ETDRS ranged from −0.084 to 0.012 logMAR, and the quadratic weighted kappa (QWK) values were >0.75 across all groups. The test–retest reliability of WHOeyes was high for both near and distance VA, with a mean difference ranging from −0.040 to 0.004 logMAR and QWK all >0.85. The questionnaire revealed an excellent user experience and acceptance of WHOeyes.

Conclusions WHOeyes could provide accurate measurement of the testing distance as well as the distance and near VA when compared to the gold standard ETDRS chart.

  • Vision
  • Low vision aid
  • Public health
  • Surveys and Questionnaires

Data availability statement

Data are available upon reasonable request.

https://doi.org/10.1136/bjo-2023-324913

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    Data availability statement

    Data are available upon reasonable request.

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    Footnotes

    • Twitter @mingguanghe

    • Contributors YW, XH and MH contributed to concept and design. YW, SZ, WW and XT contributed to experiment execution and data collection. YW, SK, VLAC and CL contributed to statistical analysis. YW, SK, VLAC, CL, XH and MH contributed to the manuscript writing and revision. XH contributed to the management of this project. XH and MH obtained funding and contributed to administrative, technical or material support. XH and MH supervised the study and acted as the guarantors of this study.

    • Funding This study was funded by National Natural Science Foundation of China (82101171) and Global STEM Professorship Scheme (P0046113).

    • Competing interests None declared.

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

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.