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- Richter, Hans, 1961-, et al.
(author)
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Prefrontal cortex activity evoked by convergence load under conflicting stimulus-to-accommodation and stimulus-to-vergence eye-movements measured by NIRS : Prefrontal cortex oxygenation and visual fatigue
- 2018
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In: Frontiers in Human Neuroscience. - : Frontiers Media S.A.. - 1662-5161. ; 12
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Journal article (peer-reviewed)abstract
- Purpose: To extend our knowledge of the functional linkages between visual fatigueand regional cerebral prefrontal cortex (PFC) oxygenation, we measured time related hemodynamic changes over the right dorsolateral prefrontal cortex (dlPFC) duringconvergence load under conflicting stimulus-to-accommodation and stimulus-tovergence eye movements with and without concurrent mental load.Methods: Twenty healthy participants with a median age of 28 years (range:18–44 years) fixated upon a vertical bar presented separately to the left andright eyes, using polarized filters, during four counterbalanced 10-min periods:(i) no accommodation/vergence conflict (Control, Ctrl); (ii) added convergenceload and accommodation/vergence conflict (Conv); (iii) added cognitive load only(Cog) and; (iv) a combination of added cognitive and convergence load andaccommodation/vergence conflict (Cc). Viewing distance was 65 cm. Non-invasivemeasurements of hemodynamic activity over the dlPFC were quantified by functionalnear-infrared spectroscopy (fNIRS). During the two-convergence load conditions, thehorizontal disparity of the two bars varied dynamically from no disparity to a disparityset 20% below the individual threshold for diplopia. Cognitive load was induced by then-back-2 test which required the subject to memorize and recall the changing colorsof the horizontal bars and decide when a given color was the same as that occurring two colors previously. fNIRS data were averaged over 10-s windows centered at 0, 2,4, 6, 8, and 10 min of each task, subtracted from a 20-s baseline window immediatelypreceding the visual task, and then represented as changes in oxygenated hemoglobin(ΔHbO2); deoxygenated hemoglobin (ΔHHb) and total hemoglobin (ΔtHb).Results: Linear mixed model analyses showed that hemodynamic activity wassystematically influenced by time (p < 0.001). The group-averaged time-related levelof change across the viewing conditions did not differ when compared with one another(p > 0.05). Larger convergence eye-movement responses under conflicting stimulus-to accommodation,and stimulus-to-vergence over time, increased ΔHbO2 and ΔtHb onlyin condition Cc and after 8 min of task time (p < 0.10 for min-6 and min-8: p < 0.05 for min-10).Discussion: Collectively, our data suggest that HbO2, HHb, and tHb, recorded over the dlPFC with fNIRS, can be used to assay the degree to which supervisory oculomotorcontrol processes are activated during visually deficient near work.
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| 2. |
- Zetterberg, Camilla, 1970-, et al.
(author)
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Workshop in visual ergonomics
- 2013
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Conference paper (peer-reviewed)abstract
- Increased use of computers is common across many work sectors. Prolonged near work at a computer screen is associated with both visual discomfort and neck/shoulder discomfort and pain. Inadequate visual ergonomics at a computer workstation can also influence both visual and neck/shoulder discomfort. The new provision from the Swedish Work Environment Authority on prevention of musculoskeletal disorders includes risk assessment of occupational visual conditions. These assessments require practitioners to have knowledge of the topic, as well as experience with practical assessment tools.The first part of the workshop proposed here will involve a presentation of the theories underlying visual ergonomic practices and a discussion of the most important factors to assess at a computer workstation. These factors include contrast, font size, resolution, glare, reflexion, non-visual flicker, and edge sharpness. The second part of the workshop, will allow participants hands-on practice in measuring and evaluating visual ergonomics at a computer workstation.
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