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Retinal implant allows blind patients to recognize letters and words

Published on Wednesday, November 3, 2010 in “Proceedings of the Royal Society B”

Researchers at the Department for Ophthalmology at the University of Tuebingen, Germany, have shown in a study that a light-sensitive chip, implanted beneath the retina, is able to restore meaningful images in blind patients, up to the point of recognizing letters and words.

The results of this study will be published on Wednesday, November 3, 2010 in “Proceedings of the Royal Society B” (doi:10.1098/rspb.2010.1747).

The subretinal electronic implant manufactured by Retina Implant AG, Tuebingen, Germany, is based on 1500 light-sensitive diodes, amplifiers and electrodes on a subretinal 3 by 3 mm chip that transforms images into a grid of electrical impulses that are transmitted to the brain via retinal neurons. Previously blind patients were able to recognize and localize sources of light or whitish objects (e.g. cups, plates).

One of the patients was able to correctly identify unknown objects and to read the hands of a large clock. Furthermore, he was able to recognize individual letters, to form words out of these letters and to distinguish 7 different shades of grey. However, in cases where the retina is scarred, insufficiently perfused or where the optic nerve is damaged, chip-mediated vision cannot be achieved.

The research aims at using a retinal implant to replace the lost function of degenerated rods and cones in the retina in patients blind from e.g. Retinitis pigmentosa. Retinitis pigmentosa, a hereditary retinal degeneration, is one of the most frequent causes of blindness at a young age. Fifteen years of research headed by Prof. Dr. Eberhart Zrenner at the Research Institute of Ophthalmology at the University of Tuebingen were necessary e.g. to find the materials that would at the same time be biocompatible while sufficiently protecting the sensitive electronic system.

It was important to determine the minimum and maximum electrical current for stimulating the optic nerve via the retina and its remaining inner nerve cell network responsible for processing and transmitting visual information to the brain. Ophthalmic surgeons had to develop a new surgical technique, enabling them to slide the chip beneath the retina while at the same time creating a connection via electric cable from inside the eye to a place behind the ear to power the chip and to provide external control and monitoring of the chip function.

Previous and future studies
In a pilot study, 11 patients received an implant, all of which had been blind for a period of 2 to 15 years. Already the first patient perceived light bars formed by individual dots of light by means of the separate test field with 16 electrodes at the implant’s tip. Five of the eleven patients were able, by means of the implant, to recognize and localize sources of light or large, whitish objects. In the case of the last three patients presented in the present paper, the chip was implanted near the macula, i.e. the place of the formerly sharpest vision. The last patient, whose results are described extensively in the present paper, was identified correctly unexpected objects (e.g. a banana or an apple), read the time from a large clock face as well and recognized individual letters and words. This publication summarized the results from two male and one female blind patient aged 40, 44 and 38 years, who had all lost their ability to read at least five years before implantation. A Europe-wide multi-centered study with additional 25 patients and an improved, cable-free version of the implant has meanwhile begun.
Title of the original publication
Journal: Proceedings of the Royal Society B
Subretinal electronic chips allow blind patients to read letters and combine them to words

doi: 10.1098/rspb.2010.1747

Eberhart Zrenner 1,*, Karl Ulrich Bartz-Schmidt 1, Heval Benav 1, Dorothea Besch 1, Anna Bruckmann 1, Veit-Peter Gabel 2,

Florian Gekeler 1, Udo Greppmaier 3, Alex Harscher 3, Steffen Kibbel 3, Johannes Koch 1, Akos Kusnyerik 1,4, Tobias Peters 5, Katarina Stingl 1, Helmut Sachs 6, Alfred Stett 7, Peter Szurman 1,Barbara Wilhelm 5 and Robert Wilke 1

1 Centre for Ophthalmology, University of Tübingen, Schleichstr. 12, 72076 Tübingen, Germany
2 Eye Clinic, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
3 Retina Implant AG, Gerhard-Kindler-Str. 8, 72770 Reutlingen, Germany
4 Department of Ophthalmology, Semmelweis University, Tomo u. 25-29, 1083 Budapest, Hungary
5 Steinbeis Transfer Centre Eyetrial at the Centre for Ophthalmology, Schleichstr. 12-16, 72076 Tübingen, Germany
6 Klinikum Friedrichstadt, Friedrichstr. 41, 01067 Dresden, Germany
7 NMI Natural and Medical Sciences Institute at the University of Tübingen, Markwiesenstr. 55, 72770 Reutlingen, Germany

Copies of the paper, images, videos and press release available from the Royal Society advance access website:

Contact for further information

Universitätsklinikum Tübingen
Department für Augenheilkunde
Forschungsinstitut für Augenheilkunde
Prof. Dr. med. Eberhart Zrenner
Schleichstr. 12, 72076 Tübingen
Tel. 07071/29-8 47 86 oder 29-8 73 11
Fax 07071/29-50 38

Dr. Ellen Katz | idw
Further information:

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