Stable eyes - A portable vestibular rehabilitation device

The vestibulo-ocular reflex (VOR) is the primary mechanism for stabilizing vision during rapid head movements. We have developed a training technique that typically increases the VOR response a minimum of 15% after 15 mins of training. This technique relies on subjects tracking a visual target that moves as a function of head motion, but at a different speed, so that the VOR is challenged to increase in order to stabilize the retinal image of the target. We have developed a portable device, StableEyes, which implements this technique so that unassisted training can be performed at home by patients with VOR hypofunction. The device consists of a head unit and base unit. The head unit contains inertial sensors to measure the instantaneous 3-D orientation of the head in space at 250 Hz, and an integrated circuit mirror to dynamically control the position of a laser target in space. The base unit consists of a touch screen interface that allows users to calibrate and set the device, in addition to recording compliance. The laser target range is ±12.5°. The device latency is 6 ms with a frequency response stable up to 6 Hz for velocities >80°/s, i.e., head velocities, where the VOR contributes most to visual stability. StableEyes was used to increase the VOR response in 10 normal subjects. In these, the VOR towards the adapting side increased by 11%, which is comparable to our laboratory findings. The adoption of StableEyes could improve the efficacy of vestibular rehabilitation and its outcomes.