# Effects of Viewing Displays from Different Distances on Human Visual System
## 1 Introduction
In addition, the algorithms show that the \(\beta\) wave decreased, but the change was more than \(\alpha\) wave with respect to the fatigue. Similarly, [PERSON] et al. [29] showed that \((\alpha+\theta)/\beta\) and \(\alpha/\beta\) significantly increased whereas \(\alpha\) and \(\beta\) waves were reduced. [PERSON] et al. [6] used the four algorithms and four frequency wavebands to evaluate the visual fatigue associated with viewing 3D TVs. The results showed that in some regions in the brain, the indicators for participants watching 3D TV varied more significantly than when the participants watched 2D TV, except for the \(\theta\) rhythm. When the participants were viewing 3D TV, the energy of \(\alpha\) and \(\beta\) frequency bands significantly decreased, while the energy of the \(\delta\) wave band significantly increased. The energy of the \(\theta\) waveband remained stable. [PERSON] et al. [5] assessed the connection between the emotional states of a teenager and relative \(\beta\)-band power at occipital lobe region while viewing 3D TV using some active and some passive glasses. The results showed that the relative \(\beta\)-band power was relatively higher while using passive (filter) glasses when compared to using active (shutter) glasses. Active 3D glasses interact wirelessly with images on a screen to enhance 3D viewing, whereas passive glasses do not [5]. With passive 3D glasses, the TV screen is coated so that light from alternate scan lines is polarized differently. The TV then interlaces two images on the screen, one for each eye. [PERSON] et al. [7] showed that the power spectral entropy is strongly correlated to visual fatigue. The results showed that the power spectral entropy reduced significantly after viewing 3D TV for a long time, thus indicating the decrease in the attention level of the participants. [PERSON] and [PERSON] [10] investigated whether the EEG power indices (\(\alpha\), \(\beta\), \(\theta\)/\(\alpha\), \(\beta\)/\(\alpha\), and \((\alpha+\theta)/\beta\)) were useful measures of visual fatigue when playing TV video games. The results revealed that the power indices of the EEG were valid indicators to measure visual fatigue. [PERSON] and [PERSON] [10] found that \(\beta\)/\(\alpha\), \(\beta\), and \(\alpha\) EEG power were good choices to measure visual fatigue, but \(\beta\)/\(\alpha\) was the best. The decreases in \(\beta\)/\(\alpha\) and \(\beta\) power indices and increase in \(\alpha\) power index were related to visual fatigue. The current stereoscopic 3D displays have several human-factor issues, including visual-fatigue symptoms such as eyestrain, headache, fatigue, nausea, and malaise. The viewing distance and viewing time are considered significant contributing factors to the visual fatigue associated with 3D displays [30; 31; 32; 33]. The viewing distance is considered an essential environmental condition and is described in the guidelines for video display terminals (VIDs) [30]. [PERSON] and [PERSON] [34] showedthat discomfort due to negative and positive conflicts in binocular disparity depends strongly on viewing distance. In addition, prolonged viewing of a 3D display increases the degree of visual fatigue [31]. [PERSON] [35] studied the long-term effects of visual fatigue from watching chromatic displays. The American Optometric Association found that prolonged use of visual systems could result in inefficient visual processing functions, which they considered visual fatigue [36]. Previous studies have focused on spectral variations in the various EEG frequency bands [5; 6; 7; 8; 9; 10; 17; 25; 26; 27]. It has often been hypothesized that through changes in attention or onset of visual fatigue, the low-frequency waves in the EEG such as \(\delta\), \(\theta\), and \(\alpha\) will increase, while the higher frequency waves such as \(\beta\) will decrease.