Conducting shorter VEP tests to estimate visual acuity via assessment of SNR

Iyer, Kartik K., Bradley, Andrew P. and Wilson, Stephen J. (2013) Conducting shorter VEP tests to estimate visual acuity via assessment of SNR. Documenta Ophthalmologica, 126 1: 21-28. doi:10.1007/s10633-012-9355-9

Author Iyer, Kartik K.
Bradley, Andrew P.
Wilson, Stephen J.
Title Conducting shorter VEP tests to estimate visual acuity via assessment of SNR
Journal name Documenta Ophthalmologica   Check publisher's open access policy
ISSN 0012-4486
Publication date 2013-02
Sub-type Article (original research)
DOI 10.1007/s10633-012-9355-9
Volume 126
Issue 1
Start page 21
End page 28
Total pages 8
Place of publication Heidelberg, Germany
Publisher Springer
Collection year 2014
Language eng
Formatted abstract
Introduction: The estimation of visual acuity (VA) via visual evoked potentials (VEP) is a valuable measure for all preverbal and non-verbal subjects whether adults or children. The aim of this study is to introduce a novel technique of VEP acquisition based on estimates of signal-to-noise ratio (SNR) and comparison to a predefined detection threshold. We aim to demonstrate the reduction in total study time without compromising the accuracy of the VEP-determined acuity estimate.

Methods: The VEP-determined acuity of twelve normal subjects was assessed via a spatial frequency (SF) sweep. A pattern reversal checkerboard stimulus utilised SFs ranging from 0.1 to 28 cycles per degree (cpd). Using linear extrapolation and Bland–Altman analysis, VEP-acquired acuity was compared to a conventional Snellen Acuity measurement. An SNR test, Fsp, assessed signal quality to determine the minimum amount of sweep data required for VEP-based VA estimation.

Results: VEP acuity estimates correlated strongly (r 2 = 0.91, SD = 0.06), leading to a VA limit via extrapolation. Bland–Altman analysis revealed agreement between tests is statistically valid (95 % CI −0.11 to 0.42 logMAR). The Fsp statistic indicated SFs 1.3–3.6 cpd yielded Fsp >3.1 within 15 s of acquisition with frequencies >3.6 cpd being sub-threshold. The Kruskal–Wallis statistic compared final Fsp values for SFs as groups, where F = 208.82 ranking each frequency, with frequencies >7.2 cpd ranking lowest.

Discussion: The Fsp as an SNR measurement shows that rapid, quality-driven clinical tests for VEP-based acuity estimates can be conducted without compromising accuracy.

Keyword Visual evoked potentials (VEP)
Snellen acuity (SA)
Spatial frequency
Signal-to-noise ratio (SNR)
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2014 Collection
School of Information Technology and Electrical Engineering Publications
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Citation counts: TR Web of Science Citation Count  Cited 3 times in Thomson Reuters Web of Science Article | Citations
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Created: Fri, 11 Jan 2013, 15:14:55 EST by Andrew Bradley on behalf of School of Information Technol and Elec Engineering