Method for measuring the visually-induced postural instability of a person

A method for measuring influence of a pair of spectacle lenses on body posture stability of a wearer comprising:

• measuring visually-induced postural instability of the wearer wearing the pair of spectacle lenses by performing a method comprising:
• providing a visual display device comprising a semi-transparent diffusive screen curved so as to have a transversal conic section and arranged to display a dynamic visual pattern in at least 50% of a lower half of a visual field of the wearer;
• displaying the dynamic visual pattern on at least a portion of the visual display device;
• and
• measuring at least one parameter representative of postural instability when the wearer is gazing at a fixed target in front of the pair of spectacle lenses while the dynamic visual pattern is displayed on the visual display device.

A device for measuring visually-induced postural instability of a person, the device comprising:

• a fixed target arranged straight in front of the person;
• a semi-transparent diffusive screen placed in the lower half visual field of the person,
• wherein the semi-transparent diffusive screen in curved so as to have a conic transversal shape,
• wherein the reflectivity of the semi-transparent screen is greater than or equal to 1% and smaller than or equal to 50%;
• a visual display device configured and arranged so as to display a dynamic visual pattern in at least 50% of a lower half visual field of the person and to leave a upper half visual field of the person free, the visual display device comprising:
• a dynamic visual pattern generating device adapted to generate the dynamic visual pattern;
• and
• a projecting device adapted to project the generated dynamic visual pattern on the semi-transparent diffusive screen placed in the lower half visual field of the person and arranged so that the person visualizes the dynamic visual pattern on the semi-transparent diffusive screen,
• wherein the dynamic visual pattern comprises at least one of:
• a movement of translation along an axis perpendicular to a vertical axis,
• a movement of translation rotating around the axis perpendicular to the vertical axis,
• a checkerboard pattern,
• an oscillating movement, and
• a periodic movement;
• and
• a measuring means configured to measure a parameter representative of postural instability of the person when the person is gazing at the fixed target straight in front while having the dynamic visual pattern displayed on the visual display device.