Blind World Magazine

Retinitis Pigmentosa.
Blind people detect light stimuli.

BioRegio STERN.
March 10, 2006.

Reutlingen-based medtech company Retina Implant AG has developed an electronic chip that is implanted in the eye under the retina and is intended to restore partial vision to many blind people. The project is now in the clinical trial stage after years of technical development. At the end of 2005, operations were successfully performed for the first time on two patients, who up to then had been completely blind.

A surgical team headed by Professor Karl Ulrich Bartz-Schmidt from Tübingen and Regensburg-based Professor Veit-Peter Gabel inserted a permanent subretinal implant in two patients on 24 and 25 October 2005 in Tübingen. The patients were then monitored over several weeks and managed to correctly identify the location and direction of spots of light and even patterns. Dr. Walter-G. Wrobel, Chairman of the Management Board of Retina Implant AG, is delighted with the results: “For the first time ever worldwide, patients who were previously blind have been able to identify electrical stimulus patterns composed of identical dots. This is fundamental proof that our subretinal implant is the right way to go.” BioRegio STERN Managing Director Dr. Klaus Eichenberg also believes the study is testimony to the innovation prevalent in the region: “This is a pioneering medical achievement that lays the foundations for use of the active microchip.”

Chip and direct stimulation field implanted under the retina in University Eye Hospital Tubingen

The scientists at Retina Implant are primarily developing the retinal implants for patients with retinitis pigmentosa, a hereditary condition that can lead to complete blindness over the course of a patient’s life. At the heart of the development is a silicon chip with miniature photosensors that control an electronic circuit so that, depending on brightness, the nerve cells in the retina are stimulated to varying degrees of intensity. These send impulses via the optic nerve to the brain. The study has now proven for the first time that the brain can actually use these signals to generate an image pattern. The clinical pilot study, supported by the German Federal Ministry of Education and Research and headed by Professor Eberhart Zrenner of the University Hospital Tübingen, was the first ever to perform chronic implantation and subretinal direct stimulation on humans.

Direct stimulation is enabled by a 4x4-array of identical electrodes located at the tip of the implant plate. The chip and direct stimulation field, which are attached to a narrow subretinal polyimide ribbon, were implanted in the two blind patients near to the macula, known as the fovea. Electrical current is supplied via the eye’s sclera with the aid of conductors in a thin cable under the skin that lead to a radio-controlled, battery-operated receiver.

According to the surgeons, there are no issues regarding local tissue tolerance and no other undesired side effects were noted. The two patients can detect light following stimulation of individual electrodes and can describe patterns generated by complex electrode arrays. The implant was removed from one patient after four weeks in line with the study plan, while the other patient chose to retain the implant. Both patients received ophthalmological and psychological care during this time. Following the initial success of the surgery in both cases, operations are to be performed on six new patients in the spring when the chip will undergo further trials.

End of article.

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