Experimental procedure for measuring and comparing head–neck–trunk posture and movements caused by different progressive addition lens designs

Abstract

This study demonstrates that appropriate measurement procedures can detect differences in head movement in a near reading task when using three different progressive addition lenses (PALs). The movements were measured using an anatomical reference system with a biomechanical rationale. This reference system was capable of representing rotations for comparing head flexion relative to trunk, head flexion relative to neck, head rotation relative to trunk and trunk flexion. The subject sample comprised 31 volunteers and three PAL designs with different viewing zones were selected. Significant differences were found between the lenses for three of the seven movement parameters examined. The differences occurred for both vertical and horizontal head movements and could be attributed to aspects of the PAL design. The measurement of the complete kinematic trunk-neck-head chain improved the number of differences that were found over those in previous studies. STATEMENT OF RELEVANCE: The study proposes a methodology based on a biomechanical rationale able to differentiate head-neck-trunk posture and movements caused by different progressive addition lens designs with minimum invasiveness. This methodology could also be applied to analyse the ergonomics of other devices that restrict the user's field of view, such as helmets, personal protective equipment or helmet-mounted displays for pilots. This analysis will allow designers to optimise designs offering higher comfort and performance.

Comparison of progressive addition lenses for general purpose and for computer vision: an office field study

“…Furthermore, eye movements as well as gaze stabilisation take longer, while the wearer needs to find the area with the optimal focus for a given viewing distance during near and intermediate tasks . A narrow progressive zone may lead to larger horizontal head movements, when reading a line of text at near or intermediate distances; thus, the co‐ordination of eye and head movements is affected . This effect can decrease performance in visual tasks across larger horizontal visual fields .…”

“…15 A narrow progressive zone may lead to larger horizontal head movements, when reading a line of text at near or intermediate distances; thus, the co-ordination of eye and head movements is affected. [16][17][18][19] This effect can decrease performance in visual tasks across larger horizontal visual fields. 20 Advances in optical lens design and fabrication have led to free-form PALs that provide a larger horizontal extent of clear vision at reading distances; the study participants also subjectively preferred these lenses.…”

Eye movements as a predictor of preference for progressive power lenses

“…Other works paid considerable attention to analyzing the relationship between the use of PPLs and the changes of the statistical descriptors of head and eye movements (EMs) when conducting visual tasks ( 32 ). In this regard, eye tracking techniques have shown some good results as tools for the characterization of optical and head movements of the user and the possible correlation with lens performance ( 9 , 8 ; 17 ; 18 ; 23 ; 28 ; 34 ). But these methods are not completely helpful to assist in the selection of the design which better fits the user because they do not correlate specific characteristics of the users with the user satisfaction with the lens.…”

“…Undistorted viewing areas calculated theoretically through the power distribution maps, do not represent the visual perception while wearing a PPL, that varies for every subject. So, in order to better understand the visual perception provided by a PPL, previous works have tried to characterize the performance of PPLs using visual tests as visual acuity (Chamorro, 2018;Chamorro et al, 2019), contrast sensitivity (Selenow et al, 2002), reading performance (Selenow, 2000;Selenow et al, 2002), adaptation to skew distortion (Habtegiorgis et al, 2018), and other measurements of optometric and/or ergonomic parameters (Alvarez et al, 2009(Alvarez et al, , 2017Mateo et al, 2010;Selenow et al, 2002). Other works paid considerable attention to analyzing the relationship between the use of PPLs and the changes of the statistical descriptors of head and eye movements (EMs) when conducting visual tasks (Rifai & Wahl, 2016).…”

“…In this regard, eye tracking techniques have shown some good results as tools for the characterization of optical and head movements of the user and the possible correlation with lens performance (Concepción et al, 2018(Concepción et al, , 2019Y. Han, Ciuffreda, Selenow, Bauer, et al, 2003;Hutchings et al, 2007;Mateo et al, 2010;Selenow et al, 2002). But these methods are not completely helpful to assist in the selection of the design which better fits the user because they do not correlate specific characteristics of the users with the user satisfaction with the lens.…”