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Hyongsok Ryu, Christian Wallraven; Out of the blue: Effects of blue-filtering lenses on EEG and eye movements during reading. Invest. Ophthalmol. Vis. Sci. 2017;58(8):866.
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© ARVO (1962-2015); The Authors (2016-present)
Increased blue-light exposure from computer screens has been linked to fatigue in screen-based working conditions, leading to the development of blue-filtering lenses. Despite this recent trend, behavioral and physiological evidence for the efficacy of such lenses is scarce. Here, we investigate potential differences in comprehension, brain wave activity, and eye movements, when people read texts with or without blue-filtering lenses.
34 participants (24 males, students, mean age=23.5y) with normal visual acuity (0.1±0.1logMar) and right eye dominance. The task consisted of reading 6 texts with different topics taken from the Korea academic aptitude test, with each text displayed for 120s and followed by comprehension questions. During the experiment, brain waves were recorded with a 24-channel electroencephalogram setup (Neurofax JE120A, 1kHz), and chin-rest-stabilized eye movements were recorded with a calibrated, monitor-based eye tracker (Tobii XL120, 120Hz). Each text contained 250 Korean words, and each syllable subtended 0.5deg visual angle. Three slides were read with blue-filtering lenses (transmittance 0% below 390nm, HOYA), and three lights with normal vision (with counter-balanced order).
Analyses used non-parametric tests in Matlab for the normal and filtered conditions on questionnaire performance, eye movement measures, and EEG band power extracted at standard frequency bands. There was no significant difference in performance (p=.578). For eye movements, the filtered condition had significantly fewer saccades per slide (244 vs 301) with longer duration (244ms vs 213ms) and length (4.1deg vs 3.6deg) (all p<.001, Fig.1). EEG analysis showed significant decreases in alpha power and increases in delta power (Fig.2) for several sites in the filtered condition.
Although we found no performance differences, several frontal EEG sites involved in attentional processes were affected by filtering, suggesting increased levels of attention. Similarly, participants made fewer and longer saccades in the filtered condition, confirming a more efficient processing of the text information. These results demonstrate for the first time clear physiological effects of blue-filtering lenses even for short usage durations.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig.1 Eye movement measures for normal and filtered conditions including p-value
Fig.2 Significant sites for alpha-decreases (red) and delta-increases (green)
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