A subretinal implant inserted under the retina of three blind people has allowed them to see shapes and objects within days of the procedure, German scientists report in the journal Proceedings of the Royal Society B. One of the patients surprised researchers by identifying and locating objects on a table; he was also able to walk around a room unaided, approach specific people, tell the time from a clock face, and describe seven different shades of gray in front of him.

The electronic visual prosthesis was developed by Retinal Implant AG, Germany and the Institute for Ophthalmic Research, University of Tuebingen, Germany. The authors describe it as an “unprecedented advance in electronic visual prostheses”.

This technology could change the lives of patients with retinitis pigmentosa – a degenerative eye disease affecting approximately 200,000 individuals globally.

Retinitis pigmentosa includes a group of inherited disorders in which abnormalities in the rods and cones in the retina – types of photoreceptors – lead to progressively worsening vision, and eventually total blindness. Patients initially suffer from night blindness, then tunnel vision in which their visual field becomes constricted, and eventually loss of central vision. Retinitis pigmentosa can occur alone or as part of a syndrome, such as Usher syndrome.

Founding Director of Retinal Implant AG, Dr. Eberhart Zrenner, said:

The results of this pilot study provide strong evidence that the visual functions of patients blinded by a hereditary retinal dystrophy can, in principle, be restored to a degree sufficient for use in daily life.

Dr. Zrenner is also Chairman of the University of Tuebingen Eye Hospital.

The subretinal implant is implanted under the retina and replaces the retina’s cones and rods – its light receptors – which were lost in retinal degeneration.

The authors explain:

It uses the eyes’ natural image processing capabilities beyond the light detection stage to produce a visual perception in the patient that is stable and follows their eye movements.

Unlike epiretinal implants which are placed outside the retina and do not use the integral light-sensitive structures in the eye, this subretinal implant does not require the patient to wear an external camera and processor.

Because this subretinal implant has considerably more light receptors than any other similar device, it gives the patient unequaled visual clarity.

Prof. Dr. Zrenner wrote:

The present study..presents proof-of-concept that such devices can restore useful vision in blind human subjects, even though the ultimate goal of broad clinical application will take time to develop.

Zrenner and team tested the device on 11 individuals. Some of them experienced no benefit because their condition had progressed too far, the researchers wrote. However, the others were able to detect bright objects and shapes.

Best results were achieved when they placed the device further behind the retina – in the central macula area. This they did with three patients.

David Head, Chief Executive at RP (Retinitis pigmentosa) Fighting Blindness, said:

This technology is very exciting; Prof Zrenner is highly respected and should be congratulated on this work. However these devices are at an early stage of development as this report notes, and it’s important that we recognize that from early trials to a product that is fully proven and generally available can take a long time. We look forward to the results of further follow up work in Oxford and other centers and we and our members will be monitoring developments with great interest.

The authors concluded in Proceedings of the Royal Society B:

These results demonstrate for the first time that subretinal micro-electrode arrays with 1500 photodiodes can create detailed meaningful visual perception in previously blind individuals.

“Subretinal electronic chips allow blind patients to read letters and combine them to words”

Eberhart Zrenner, Karl Ulrich Bartz-Schmidt, Heval Benav, Dorothea Besch, Anna Bruckmann, Veit-Peter Gabel, Florian Gekeler, Udo Greppmaier, Alex Harscher, Steffen Kibbel, Johannes Koch, Akos Kusnyerik, Tobias Peters, Katarina Stingl, Helmut Sachs, Alfred Stett, Peter Szurman, Barbara Wilhelm, Robert Wilke

Proceedings of the Royal Society B Published online before print November 3, 2010

doi: 10.1098/rspb.2010.1747

Written by Christian Nordqvist