An Objective and Sensitive Visual Acuity Assessment Method for Preverbal and Infantile Children Based on Steady-State Motion Visual Evoked Potentials

Abstract

Traditional evaluation of visual acuity, such as naming of Snellen letters, mainly depends on the subjective examiner’s judgement, which can be easily affected by the impure motivational factors or intellectual abilities, so it may be more difficult for infants. By recording and analyzing electrophysiologic signals especially steady-state motion visual evoked potentials (SSMVEPs) from the human scalp, an objective, quantitative and sensitive method of evaluating objective visual acuity and monitoring the visual development of preverbal and infantile children can be provided. In this study, we designed a specific concentric ring SSMVEP paradigm with a given oscillating expansion-contraction frequency to assess the visual acuity. The canonical correlation analysis (CCA), signal-to-noise ratio (SNR) and some statistical methods were used to analyze the electroencephalography signals and extract visual acuity features in the test. We proposed a threshold determination method to define the corresponding objective visual acuity and established a representational model of the objective visual acuity. Each experiment was divided into 11 trails of different spatial frequencies corresponding to SSMVEP optotypes from 0.0 to 1.0 log minimum angle of resolution (logMAR), and the objective visual acuity of 22 eyes from 11 healthy adults had been tested using this paradigm with brain computer interface system. The CCA value at the target stimulus frequency of SSMVEP response had a decreasing trend from 1.0 logMAR to 0.0 logMAR SSMVEP optotype. The objective SSMVEP visual acuity and subjective psychophysical visual acuity were correlated significantly (P = 7.4708E-12, Pearson’s r = 0.9532), and the difference between the two types of visual acuity of the same eye was within 0.1 logMAR range, except one eye with 0.2 logMAR difference. Our study proved that SSMVEP can be an objective and quantitative method to measure visual acuity, especially for evaluating and monitoring visual acuity of infants and preverbal children.