Background

for investigating the functional condition of the vestibular apparatus

  • The visual and vestibular systems interact to maintain visual clarity of objects during head movement.
  • The fovea is the part of the eye that has the greatest density of photoreceptors and therefore is the area with the best visual acuity.
  • During motion, the image of the viewed object tends to slip from the fovea, causing it to blur.
  • In fact, visual acuity declines to 50 % when an object is 2° from the centre of the fovea.
  • To maintain an object on the fovea, the eye must make corrective responses.
  • These corrective eye movements, known as Nystagmus, have a slow phase and a quick phase.
  • The vestibuloocular reflex (VOR) slow phase keeps the eyes on the foveal vision (opposite direction to head movement).
  • During rotational chair testing, eyes move in a direction opposite to the rotation of the chair (slow phase eye movements).
  • The Nystagmus observed is a physiological response and observed with acceleration and deceleration of rotation.
  • Sustained constant rotation without vision results in a decline of this Nystagmus.
  • Nystagmus attempts to help stabilise the visual field during movement.
  • Our semi-circular canals are responsible for informing the brain about our rotational movements and they are mostly unaffected by gravity.

Background

Solution

the general reaction of the body to rotation is observed

  • Rotation of the chair is performed that the stimulus applied to the whole body is the same as a stimulus that is applied to the head.
  • The head may be strapped to the chair during rotation.
  • The trainee is sitting on the chair, blindfolded. Then rotates about the vertical axis while keeping his head upright, tilted forward/backward or turned to the left or right side.
  • Then the trainee is asked to perform tasks such as determine his direction of rotation while blindfolded, or rapidly change the orientation of his head, or attempt to point at a stationary object without blindfold after the chair stops.
  • The chair is used to demonstrate spatial disorientation effects, proving that the vestibular system is not to be trusted in flight. Because of this reason, pilots are told that they should rely on their flight instruments.

Solution

Features

The training system will provide the following features:

Chair frame

Chair frame

Chair frame including upper and lower steel frame, mountable on the floor.
Servomotor with power supply, transmissions, sensors and controller including interface to a computer.
Headrest and armrests

Headrest and armrests

Headrest, armrests and additional leg and foot rest. This guarantees that the trainees feet will not touching the floor. Adjustable support for the back, head, feet and arms in order to provide training for different human body sizes. 2-point lap seat belt, which ensures the safety of the trainee and which gives the trainee the possibility to bend over head and body towards the knees.
Control computer

Control computer

Control computer with interface to the motor controller. Drive control software for the setup of reference values for speed and acceleration. Start/Stop operator panel with emergency stop button for the operator. The control and safety system is a hardware based safety circuit.

References

Kingdom of Saudi Arabia 2014

Kingdom of Saudi Arabia 2014

Two units of the Barany Chair have been delivered in 2014.
The Netherlands 2013

The Netherlands 2013

The first unit was delivered in 2013.