A group of researchers from the University of Fribourg in Switzerland, China and the USA has made a discovery which could form the basis of a new generation of visual prostheses. They have demonstrated that tree shrews can “see”, even without retinal stimulation. The nerve cells of the mammals were activated by light, thereby generating visual percepts in the brain.

Stimulation of the visual system usually occurs by activating the retina in the eye. The interdisciplinary group of researchers, led by Prof. Gregor Rainer of the University of Fribourg, has now succeeded in technically inducing such stimulation by activating the relevant nerve cells without any visual information reaching the eye at all. Thanks to optogenetics, a technique where channel proteins are introduced into nerve cells in the brain, it was possible use light to stimulate these nerve cells.

When the brain can see – even without eyes
In principle, this technique makes it possible to feed information into the visual system which can then be interpreted as sight, even in the event of sight loss. Current findings could therefore form the basis of the next generation of visual prostheses. Further targeted research work will be necessary before this can become a reality. At present, visual prostheses involve a surgical procedure stimulate the eye. They can help to remedy certain eye diseases, but no real breakthrough has been achieved so far.

The current studies focus not on the eye, but on the visual thalamus, a relay centre in the brain where information from the eyes is collected and passed on. Further basic research is now needed to come as close as possible to natural sight by means of technically induced visual percepts.

Animal model as the basis for insights into a global problem
Thanks to their highly developed visual system and its similarity to the human equivalent, tree shrews are well suited for work on visual prosthetics. Switzerland’s high standards about medical research on laboratory animals ensure that these studies are carried out according to the highest welfare standards.

The World Health Organization estimates that at least 2.2 billion people worldwide suffer from near or distance vision impairment. Most people with vision impairment and blindness are over the age of 50 years. It is hoped that further research in this field will lead to the development and testing of innovative visual prostheses in the medium term. This would improve the quality of life for many people, particularly in societies with an ageing demographic.