Analysis of real-world visual ergonomics at the visual display unit

Abstract

Introduction: In this interventional study, the ergonomic workplace set-up and the impact of character size on subjectively estimated working productivity and computer vision syndrome (CVS) were evaluated in the field.

Methods: The number of displays and their size, resolution, surface structure, position in the room and relation to the eye were evaluated for 152 units. CVS was assessed using the CVS-Questionnaire. Habitually used character size for an uppercase E was recorded and compared to the ISO 9241-303:2011, national standards (e.g., ANSI/HFES 100-2007) and national guidelines (e.g., German DGUV Information 215-410). In case of failure to comply with these standards, character size was increased to 22 angular minutes to reach the recommended ranges. Reasons for returning to former or smaller character sizes were recorded, and subjectively perceived changes in productivity were estimated by the participants using a visual analogue scale before and 2 weeks after the intervention using a questionnaire.

Results: The average visual display unit consisted of two non-glare (matt) 24″ widescreen monitors that were located approximately 73 cm (primary) and 76 cm (secondary) from the eyes. The mean (SD) habitually set character size was 14.29 angular minutes (3.53) and therefore both statistically and clinically significantly too small compared with ISO 9241-303:2011 (p < 0.001). Increasing the character size to 22 angular minutes produced a 26% reduction in subjectively rated productivity (p < 0.001). No significant correlation between character size and symptoms of CVS was demonstrated.

Conclusions: In the workplaces investigated, recommendations for character size were not adhered to. This resulted in a reduction in productivity and was not compatible with some of the work requirements, for example, obtaining a broad overview of a spreadsheet.

Keywords: character size; visual display unit; visual ergonomics.