A visual ergonomics intervention in mail sorting facilities: Effects on eyes, muscles and productivity Hillevi Hemphälä a, c, * , Jörgen Eklund b, c a Division of Ergonomics and Aerosol Technology, Design Sciences, Lund University, P.O. Box 118, SE-22100 Lund, Sweden b Division of Ergonomics, School of Technology and Health, Royal Institute of Technology, KTH, Alfred Nobels Allé 10, SE-14152 Huddinge, Sweden c Division of Industrial Ergonomics, Department of Management and Engineering, Linköping University, SE-581 83 Linköping, Sweden 1 article info Article history: Received 18 February 2008 Accepted 4 May 2011 Keywords: Lighting Postmen Sorting Illuminance MSD Vision Eyestrain abstract Visual requirements are high when sorting mail. The purpose of this visual ergonomics intervention study was to evaluate the visual environment in mail sorting facilities and to explore opportunities for improving the work situation by reducing visual strain, improving the visual work environment and reducing mail sorting time. Twenty-seven postmen/women participated in a pre-intervention study, which included questionnaires on their experiences of light, visual ergonomics, health, and musculo- skeletal symptoms. Measurements of lighting conditions and productivity were also performed along with eye examinations of the postmen/women. The results from the pre-intervention study showed that the postmen/women who suffered from eyestrain had a higher prevalence of musculoskeletal disorders (MSD) and sorted slower, than those without eyestrain. Illuminance and illuminance uniformity improved as a result of the intervention. The two post- intervention follow-ups showed a higher prevalence of MSD among the postmen/women with eyestrain than among those without. The previous differences in sorting time for employees with and without eyestrain disappeared. After the intervention, the postmen/women felt better in general, expe- rienced less work induced stress, and considered that the total general lighting had improved. The most pronounced decreases in eyestrain, MSD, and mail sorting time were seen among the younger participants of the group. Ó 2011 Elsevier Ltd and The Ergonomics Society. All rights reserved. 1. Introduction and background A literature search for studies on longitudinal lighting inter- ventions and eyestrain in a non-computer environment was performed but no internationally published peer reviewed articles were found. Aarås et al. (1998,2001) performed a large ergonomic intervention study of video display units (VDU) operators, which included lighting. They found that lighting and optometry are of crucial importance in reducing musculoskeletal disorders (MSD). Both mail sorting and VDU work is visually demanding, and a good visual environment is important for health and wellbeing. 1.1. Visual ergonomics and lighting When vision is unsatisfactory, the body adapts to a posture aimed at improving it: "The eyes lead the body" (Anshel, 2005). The frequency of musculoskeletal pain among people with incor- rect lenses in their glasses is higher than among those with correct lenses. A single vision lens or a work progressive lens is better for working with computers than a regular progressive lens (Horgen, 2003). People with eyestrain often also report musculo- skeletal complaints (Knave et al., 1985). Studies show that an optic correction for near distance work affects the accommodation and vergence, which reduces muscle activity in the head, neck, and shoulder region (Lie and Watten, 1985, 1994; Richter, et al., 2010a,b). This means that a pair of working glasses adjusted for correct working posture and distances can reduce muscle strain. There are also differences in eyestrain within a working day: The amount usually increases when the same type of work is performed (Boyce et al., 2005). The visual environment can change the mood of people, which can alter their behaviour (Boyce, 2004). Human performance can * Corresponding author. Division of Ergonomics and Aerosol Technology, Design Sciences, Lund University, P.O. Box 118, Sölvegatan 26, SE-22100 Lund, Sweden. Tel.: þ46 709 428150; fax: þ46 46 2223936. E-mail address: hillevi.hemphala@design.lth.se (H. Hemphälä). 1 Former affiliation. Contents lists available at ScienceDirect Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo 0003-6870/$ e see front matter Ó 2011 Elsevier Ltd and The Ergonomics Society. All rights reserved. doi:10.1016/j.apergo.2011.05.006 Applied Ergonomics 43 (2012) 217e229