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A comparison of contrast sensitivity and sweep visual evoked potential (sVEP) acuity estimates in normal humans

  • William H. RidderIIIEmail author
Original Research Article

Abstract

Purpose

Several previous studies have demonstrated that for normal adult subjects the optotype acuity measured with charts is better than the acuity determined with the sweep visual evoked potential (sVEP) using gratings or checks. However, there is no difference in psychophysical measures of acuity with optotype or grating charts. Thus, it is unclear whether the acuity discrepancy between optotype charts and the sVEP result from the stimulus design or other methodological differences. The purpose of this experiment is to determine the relationship between acuities extrapolated from a contrast sensitivity function (CSF) that uses optotypes and the sVEP.

Methods

Normal subjects (N = 10) with acuity of 0.00 logMAR or better (ETDRS chart) were recruited for this study. Two commercially available systems were used to measure CSFs [i.e., the Beethoven System (Ryklin Software, NY) and the qCSF system (Adaptive Sensory Tech, CA)]. The stimuli for the Beethoven were sine wave gratings (0.75–18.50 cpd), and thresholds were determined with a 2-alternative forced choice (2-AFC) procedure combined with a staircase. The stimuli for the qCSF system were spatially filtered letters (10 possible letters, 10-AFC) with the letter sizes and contrasts determined by a Bayesian adaptive procedure. Visual acuity was determined by fitting the data with a double exponential equation and extrapolating the fit to a contrast sensitivity of one. The sVEP was obtained with the PowerDiva (Digital Instrumentation for Visual Assessment, version 3.5, CA). The stimuli were sine wave gratings (80% contrast, 3–36 cpd) counterphased at 7.5 Hz. The final acuity was the average of two estimates each derived from the average of 10 sweeps.

Results

The average logMAR chart (acuity converted to cpd), sVEP, Beethoven, and qCSF acuities were 36.6 ± 4.62 cpd (mean ± SD), 31.2 ± 4.59 cpd, 27.3 ± 7.38 cpd, and 27.6 ± 6.36 cpd, respectively. The logMAR chart acuity was significantly different from the other acuity estimates (all p values < 0.05). The sVEP, Beethoven, and qCSF acuities were not different from one another (all p values > 0.05). The Beethoven and the qCSF acuities had a good intraclass correlation coefficient (ICC = 0.85).

Conclusions

Similar to previous publications, the sVEP acuity estimate was less than the optotype chart acuity. The acuity determined with the sVEP and the CSFs with letter and grating stimuli were not statistically different, suggesting that the difference in acuity with the sVEP and optotype charts does not result from stimulus differences. Other methodological differences must account for the discrepancy in sVEP and optotype chart acuity.

Keywords

Visual acuity Contrast sensitivity Sweep visual evoked potential Optotypes 

Notes

Acknowledgements

The author is grateful to Apoorva Karsolia and Deborah Duan for some of the data collection.

Funding

No funding was received for this research.

Compliance with ethical standards

Conflict of interest

The author declares he has no conflict of interest.

Statement of human rights

All procedures performed in studies involving human participants were in accordance with the ethical standards of Ketchum University and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Statement on the welfare of animals

There were no animals used in this study.

Informed consent

Informed consent was obtained from all individual participants included in the study.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Marshall B. Ketchum University, Southern California College of OptometryFullertonUSA

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