Vertical gaze direction and postural adjustment: An extension of the Heuer model.

Abstract

The authors provide a consideration of the vergence system and suggest an extension of the original model proposed by H. Heuer, M. Drawer, T. Romer, H. Kroger, and H. Knapp (1991) to explain why preferred vertical gaze angle is downward when fixating proximal targets. The practical implication of the revised model is that heterophoria (open-loop vergence bias) provides an indication of potential vergence effort. The extended model has several advantages: It allows for modification of workstations, is consistent with models of the accommodation and vergence system, is compatible with clinical data, and provides a more complete explanation of extant research data. The extended model was able to predict oculomotor responses, explain postural adjustments, and provide economically useful data. This article is concerned with the issue of why observers prefer to view proximal targets with declined gaze. We modify an extant model that relates this phenomenon to the angle of ocular vergence, and we suggest a simple method of assessing the relationship between vertical gaze direction and vergence effort. We then extend our research to explore the interactions between preferred gaze angle and postural adjustment in

Fixation Disparity: Binocular Vergence Accuracy for a Visual Display at Different Positions Relative to the Eyes

“…Given that fixation disparity is correlated with the resting position of vergence (Jaschinski-Kruza, 1994), we conclude that changes in fixation disparity with gaze inclination are induced by inclination effects in the resting position. These observations correspond to findings of Heuer and Owens (1989); Jaschinski, Koitcheva, et al (1998);and Mon-Williams et al (1998), and to a result of Mon-Williams et al (1999). Heterophoria showed a near shift at lower eye inclination but was not significantly different at viewing distances of 33, 50, and 100 cm.…”

Restricting the Vertical and Horizontal Extent of the Field-of-View: Effects on Manoeuvring Performance

“…Also, during the stepping over task, more errors were made with an upward oriented view. This is in line with work by Mon-Williams and colleagues [21], who state that high gaze angles quickly cause visual fatigue, which may account for the performance decrements found here. Another cause could be the disturbance of the vestibular system that is caused by the altered head orientation, which is needed to compensate for the change in visual field orientation.…”

The influence of desk and display design on posture and muscle activity variability whilst performing information technology tasks

“…It is generally accepted that a downward gaze angle is beneficial for visual comfort (Mon-Williams et al, 1999;Sommerich et al, 2001). A consideration of postural mechanics, however, dictates that the increase in head tilt required to accommodate lower displays increases the gravitational moment, and therefore the muscular torque required to maintain this flexed posture.…”