Abstract
Purpose: :
The purpose of this study was to determine whether unperceived dynamic ophthalmic distortions could have a significant impact on postural control.
Methods: :
We used a full immersive virtual environment to simulate dynamic distortions normally produced by ophthalmic lens corrections for myopes and hyperopes. The subjects were in standing position with feet together and arms crossed. Their task was to track a red ball with their eyes that was moving on the horizontal axis. While tracking the ball, a dynamic distortion model was applied to the background room represented in a form of a grid. The subjects reported no awareness of the distortion that was applied to the background grid room. Body sway amplitude was calculated from the Flock of Birds electromagnetic trackers positioned on the body. Subjective discomfort was evaluated for each condition with the Unit Subjective Discomfort Scale.
Results: :
The data show clear postural reactivity as a function of dynamic distortions for both negative and positive distortions normally generated for myopic and hyperopic corrections. The postural reactivity increased as a function of amplitude of the distortion demonstrating that it was the distortion itself that was generating postural reactivity.
Conclusions: :
This is the first clear evidence that unperceived dynamic visual distortions have significant effects on postural control. This must be taken into consideration when adapting patients to new ophthalmic lenses and predicts an increased difficulty level of adaptation for patients with strong ammetropias.
Keywords: spectacle lens • vision and action • scene perception