Abstract
In natural uncorrected vision in young observers, a given eccentric fixation target at any distance can be fixated by various combinations of eye and head position with an identical resulting visual input. The properties of the visual input do not depend on the rotational status of the eye. In contrast, the quality of visual input strongly depends on eye position in progressive lens wearers. A specific eye position provides clear, focused vision at a specific distance only. Thus for fixating a target with clear vision, one specific optimal combination of eye and head position exists in a progressive lens wearer. Especially in challenging visual situations a change in eye head coordination is therefore a prerequisite for successful task performance. In modern everyday life, car driving is one of the strongest visual challenges, where a large field of view is scanned permanently with coordinated eye-head-movements. Although free to move their gaze and head, car driver’s fixational behavior is constantly determined by the tasks requirements. In progressive lens wearers, specific head movements might therefore be enforced during driving. In the present study, changes in head-movement behavior are shown in progressive lens wearers during driving compared to controls. Progressive lens wearers and controls performed a real-world driving task, each of them driving along the same predefined urban round course track in Stuttgart downtown. Eye head coordination of progressive lens wearers was analyzed with respect to three main parameters: head gain, temporal properties in head movements and variance in head movements. Changes in head movement behavior, specific to progressive lens wearers, were determined in all three parameters, pointing towards complex changes in eye-head-coordination induced by the modification of optical properties in a progressive lens. Therefore, the varying optical properties of a progressive lens can be interpreted as visual learning signal for eye-head-coordinated movements.
Meeting abstract presented at VSS 2015