Gunawardane P D S H, MacNeil R R, Zhao L, Enns J T, de Silva C W, Chiao M
IEEE Trans Biomed Eng. 2021 Oct;68(10):3048-3058. doi: 10.1109/TBME.2021.3062256. Epub 2021 Sep 20.
Electrooculography (EOG) can be used to measure eye movements while the eyelids are open or closed and to assist in the diagnosis of certain eye diseases. However, challenges in biosignal acquisition and processing lead to limited accuracy, limited resolution (both temporal and spatial), as well as difficulties in reducing noise and detecting artifacts. Methods such as finite impulse response, wavelet transforms, and averaging filters have been used to denoise and enhance EOG measurements. However, these filters are not specifically designed to detect saccades, and so key features (e.g., saccade amplitude) can be over-filtered and distorted as a consequence of the filtering process. Here we present a model-based fusion technique to enhance saccade features within noisy and raw EOG signals. Specifically, we focus on Westheimer (WH) and linear reciprocal (LR) eye models with a Kalman filter. EOG signals were measured using OpenBCI's Cyton Board (at 250 Hz), and these measurements were compared with a state-of-the-art EyeLink 1000 (EL; 250 Hz) eye tracker. On average, the LR model-based KF produced a 47% improvement of measurement accuracy over the bandpass filters. Thus, we conclude that our LR model-based KF outperforms standard bandpass filtering techniques in reducing noise, eliminating artifacts, and restoring missing features of saccade signatures present within EOG signals.
眼电图（EOG）可用于在眼睑睁开或闭合时测量眼球运动，并辅助诊断某些眼部疾病。然而，生物信号采集和处理方面的挑战导致其准确性有限、分辨率受限（包括时间和空间分辨率），以及在降低噪声和检测伪迹方面存在困难。诸如有限脉冲响应、小波变换和平均滤波器等方法已被用于对EOG测量进行去噪和增强。然而，这些滤波器并非专门设计用于检测扫视，因此关键特征（如扫视幅度）可能会因滤波过程而被过度滤波和扭曲。在此，我们提出一种基于模型的融合技术，以增强噪声和原始EOG信号中的扫视特征。具体而言，我们重点关注采用卡尔曼滤波器的韦斯特海默（WH）眼模型和线性倒数（LR）眼模型。使用OpenBCI的Cyton板（250赫兹）测量EOG信号，并将这些测量结果与最先进的EyeLink 1000（EL；250赫兹）眼动仪进行比较。平均而言，基于LR模型的卡尔曼滤波器在测量精度上比带通滤波器提高了47%。因此，我们得出结论，我们基于LR模型的卡尔曼滤波器在降低噪声、消除伪迹以及恢复EOG信号中存在的扫视特征的缺失特征方面优于标准带通滤波技术。
