July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Assessing visual acuity – test-retest repeatability and level of agreement between the electronic ETDRS chart (E-ETDRS), optokinetic nystagmus (OKN), and sweep VEP
Author Affiliations & Notes
  • Lily Yu-Li Chang
    Optometry & Vision Science , University of Auckland, Auckland, New Zealand
    Auckland Bioengineering Institute , University of Auckland, Auckland , New Zealand
  • Peng Guo
    Auckland Bioengineering Institute , University of Auckland, Auckland , New Zealand
  • Ben Thompson
    Optometry and Vision Science , University of Waterloo, Waterloo, Ontario, Canada
  • Mehrdad Sangi
    Uniservices, University of Auckland , Objective Acuity Ltd , Auckland , New Zealand
  • Jason Turuwhenua
    Auckland Bioengineering Institute , University of Auckland, Auckland , New Zealand
    Optometry & Vision Science , University of Auckland, Auckland, New Zealand
  • Footnotes
    Commercial Relationships   Lily Yu-Li Chang, None; Peng Guo, None; Ben Thompson, Objective Acuity Ltd (C), Objective Acuity Ltd (P); Mehrdad Sangi, Objective Acuity Ltd (E); Jason Turuwhenua, Objective Acuity Ltd (C), Objective Acuity Ltd (P)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 5789. doi:
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      Lily Yu-Li Chang, Peng Guo, Ben Thompson, Mehrdad Sangi, Jason Turuwhenua; Assessing visual acuity – test-retest repeatability and level of agreement between the electronic ETDRS chart (E-ETDRS), optokinetic nystagmus (OKN), and sweep VEP. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5789.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The gold standard measure of visual acuity (VA), the ETDRS chart, relies on subjective patient responses. This can result in low testability in children and patients with cognitive impairment. Objective measures of VA may solve this problem. We investigated the use of objective VA measures (OKN and sweep VEP) in healthy adults. Our hypotheses were 1) objective methods would have high test-retest repeatability, and 2) VA results would be strongly correlated across the different techniques.

Methods : Monocular unaided visual acuity was measured for each eye in 10 healthy adult participants (21.9 ±1.10 years, mean spherical equivalent, -0.71 ±1.28 DS), using E-ETDRS (Jaeb Center for Health Research, USA), OKN (bull’s eye stimulus array with stroke widths equivalent to logMAR 1.0-0.0 in 0.1 steps, 5 trials per logMAR level, stimulus speed 7 deg/s), and sweep VEP (Roland Consult, Havel, Germany). E-ETDRS and sweep VEP both provided a numerical logMAR output. OKN videos were analysed trial by trial, using a mixed subjective (judged by clinical observer) and objective (image processing) protocol. OKN was judged to be present or absent on each trial. Test-retest repeatability and correlations were assessed using Spearman’s Rho because data were non-parametric.

Results : Test and retest measures were strongly correlated within each technique, with the highest correlation being for OKN (r=0.959, p<0.01. Mean logMAR for test +0.31±0.26 vs. retest +0.28±0.27) followed by E-ETDRS (r=0.928, p<0.01. Mean logMAR for test +0.27±0.41 vs. retest +0.25±0.41) and sweep VEP (r = 0.882, p<0.01. Mean logMAR for test +0.10±0.40 vs. retest +0.20±0.34). The OKN VA measure was strongly correlated with the E-ETDRS measure (r=0.865 p<0.01). The sweep VEP measure was not correlated with E-ETDRS (r=0.220, p>0.05).

Conclusions : In healthy adult participants, test retest repeatability was high for all three techniques. Visual acuity measurements by OKN had the best test retest repeatability, and OKN measures were strongly correlated with E-ETDRS measures. Objective measurement of VA has a role in clinical testing, and further investigation of the OKN technique is warranted in populations that can be challenging to test using ETDRS, such as preverbal children and patients with dementia.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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