Assessment of Human Visual Acuity Using Visual Evoked Potential: A Review

Abstract

Visual evoked potential (VEP) has been used as an alternative method to assess visual acuity objectively, especially in non-verbal infants and adults with low intellectual abilities or malingering. By sweeping the spatial frequency of visual stimuli and recording the corresponding VEP, VEP acuity can be defined by analyzing electroencephalography (EEG) signals. This paper presents a review on the VEP-based visual acuity assessment technique, including a brief overview of the technique, the effects of the parameters of visual stimuli, and signal acquisition and analysis of the VEP acuity test, and a summary of the current clinical applications of the technique. Finally, we discuss the current problems in this research domain and potential future work, which may enable this technique to be used more widely and quickly, deepening the VEP and even electrophysiology research on the detection and diagnosis of visual function.

Enhancing Performance of SSVEP-Based Visual Acuity via Spatial Filtering

“…Here, we aimed to compare the effect on visual acuity assessment by SSVEPs with different spatial filtering methods to combine multielectrode signals into a single-channel signal. The visual acuity results depend on the SSVEP amplitude changes versus spatial frequencies ( Zheng et al, 2020c ), and the SSVEP amplitude is usually obtained from single-channel SSVEP by using Fourier analysis to transform an SSVEP signal from the time domain to the frequency domain and extracting the specific SSVEP amplitude at the fundamental frequency of the visual stimulus from the resulting spectrum ( Hamilton et al, 2021a , b ). Hence, here, we only focused on the single-channel spatial filtering methods, i.e., N c = 1, and W = w ∈ R N e ×1 .…”

“…The native combination is also called the monopolar combination where only the SSVEP signals from one of the electrodes are analyzed ( Friman et al, 2007 ; Zerafa et al, 2018 ). In the SSVEP analysis, the most used electrode is Oz ( Yan et al, 2021 ; Zheng et al, 2020c ). Assuming that the SSVEP signals from the Oz electrode are corresponding to the first column in N e -electrode SSVEP signals Y (same below), the spatial filtering weights w can be expressed as:…”

“…In this study, the vertical sinusoidal gratings with a reversal frequency of 7.5 Hz were used as the visual stimuli with the Michelson contrast of 50% and the mean background luminance of 80 cd/m 2 ( Kurtenbach et al, 2013 ; Zheng et al, 2020c ). The visual angle of the stimulus pattern with a side length of 720 pixels was set as four degrees by adjusting the distance between the display and subjects.…”

“…In the SSVEP analysis, the most used electrode is Oz (Yan et al, 2021;Zheng et al, 2020c). Assuming that the SSVEP signals from the Oz electrode are corresponding to the first column in N e -electrode SSVEP signals Y (same below), the spatial filtering weights w can be expressed as:…”

“…In general, it is mainly tested by psychophysical methods, e.g., Sloan letters and tumbling E charts ( Ricci et al, 1998 ). However, these methods require the subjects to have sufficient intelligence to comply with the test process and are hard for preverbal or infantile children, the mentally disabled, and malingerers ( Incesu and Sobaci, 2011 ; Zheng et al, 2020c ).…”