Well-established charts such as Early Treatment Diabetic Retinopathy Study are able to quantify visual acuity (VA) with a low cutoff of 1.6 logMAR. Below this point, nonquantitative measures, such as count fingers, hand movements, and light perception, are used. There is a need for more reproducible, comparable, and reliable ways to measure VA changes in this patient cohort.
The purpose of this study was to examine and compare the ability of the Berkeley Rudimentary Vision Test (BRVT) and the Freiburg Acuity Test (FrACT) to quantify VA in low-vision patients who score nonnumerical VAs in standard charts.
Fifty adult participants with VA ≤1.0 logMAR in both eyes were recruited from the Oxford Eye Hospital, Oxford, United Kingdom. Correlation between FrACT and BRVT results and the correlation between VA and daily living activities were analyzed statistically. Potential predictors of differences were investigated.
The BRVT was significantly faster to conduct (P = .002), but FrACT was able to quantify vision numerically in a greater proportion of eyes. The κ agreement between tests was 0.26. The difference increased systematically with the VA reduction (P < .0001). The Bland-Altman analysis showed a skew to measurement of lower logMAR VA indicating better vision measured on the FrACT. The only significant predictor of difference between the tests was binocular VA (coefficient, −0.445; P = .001).
Both tests are suitable for a very low-vision population. The BRVT is a faster test to administer, but FrACT provides a numerical result in more eyes. The poor intertest repeatability indicates that they cannot be used interchangeably. The BRVT generally reported poorer vision than did the FrACT. The medium of presentation, such as a computer screen or externally lit print medium, is likely to be the biggest factor in these differences and warrants further investigation.
1Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
2Oxford Biomedical Research Centre, Oxford Eye Hospital, John Radcliffe Hospital, Oxford, United Kingdom *enquiries@eye.ox.ac.uk
Supplemental Digital Content: Appendix 1, the questionnaire used during the study, is available at http://links.lww.com/OPX/A398).
Appendix Figure A1, a flowchart showing the vision testing protocol for the Berkeley Rudimentary Vision Test and providing a scoring guide, is available at http://links.lww.com/OPX/A399).
Appendix Table A1, contrast measurements of the tests in situ at different test distances, is available at http://links.lww.com/OPX/A400). The contrast was calculated by measuring dark and light areas on the charts under the illumination used for testing as specified in themethods. This was done using a light meter, Sekonic L-758Cine DigitalMaster (Sekonic Corporation, Tokyo, Japan) then calculating the Weber contrast. A large E was used in both tests for the measurement.
Submitted: January 16, 2018
Accepted: February 9, 2019
Funding/Support: The research was funded by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC), based at Oxford University Hospitals NHS Trust and University of Oxford.
Conflict of Interest Disclosure: All authors were employed by the National Health Service at the time of this work taking place.
Study Registration Information: National Health Service Research Ethics Committee (13/SC/0234).
Author Contributions and Acknowledgments: Conceptualization: JKJ, REM; Data Curation: JKJ, JMG, APS; Formal Analysis: JKJ, JMG, APS, RCH; Funding Acquisition: REM; Investigation: JKJ, REM; Methodology: JKJ; Project Administration: JKJ, JMG; Resources: JKJ, REM; Supervision: JKJ, REM; Validation: APS, REM; Visualization: JKJ, RCH; Writing - Original Draft: JKJ; Writing - Review & Editing: JMG, APS, RCH, REM.
The views expressed are those of the authors and not necessarily those of the National Health Service, the National Institute for Health Research, or the Department of Health. The sponsor and funding organization had no role in the design or conduct of this research.
The authors would like to thank Tallulah Shepherd for her contribution to data collection.
Supplemental Digital Content: Direct URL links are provided within the text.
Online date: May 2, 2019
