Fitting a bionic eye to the body: how haptics can help

The function of any visual prosthetic will be to generate patterned stimulation of the visual cortex arising from either direct stimulation (e.g. using cortical implants) or more peripheral inputs (e.g. an artificial retina). Direct cortical stimulation may result in patterns containing relatively few elements (say 10-100) while an artificial retina may deliver more complex patterns. We propose that regardless of the site of intervention, a tactile copy of the input, delivered to the skin at the same time as it is sent to the visual cortex, will offer significant advantages, especially during early stages of testing and development in which the user must 'make sense' of the novel input. The advantages of such a display include: (1) exploitation of multisensory processes such as cross-calibration, learning to discriminate sub-threshold stimuli and perceptual redundancy, (2) a means of measuring strengths and weaknesses of the prosthetic's visual input and evaluation of improvements and (3) a way of quickly adapting the congenitally- or late-blind user to the prosthetic