Updates on the Progress of Clinical Trials for a Retinal Implant for Retinitis Pigmentosa

The retinal implant in place in the human eye

An updated study, entitled Artificial vision with wirelessly powered subretinal electronic implant has been published online in the February 2013 issue of Proceedings of the Royal Society B: Biological Sciences. Proceedings B is the Royal Society’s biological research journal, dedicated to the rapid publication of high-quality research papers.

The paper summarizes the results of a nine-subject clinical trial of a functional retinal implant for patients with retinitis pigmentosa. The retinal implant project is headed by Eberhart Zrenner, M.D., founding director of the Institute for Ophthalmic Research in Tübingen, Germany. The retinal implant was developed with funding from the German government and Retinal Implant AG.

The study is authored by lead author Katarina Stingl and colleagues who represent the following institutions: University of Tübingen, Germany; Semmelweis University, Budapest, Hungary; Clinic Friedrichstadt, Dresden, Germany; Retina Implant AG, Reutlingen, Germany; and Klinikum Stuttgart, Stuttgart, Germany.

How the Retinal Implant Device Works

A cable from the implanted chip in the eye leads under the temporal muscle to exit behind the ear and connects with a wirelessly operated power control unit. The wireless power control unit is a small handheld external device, attached to a neckband that allows the unit to rest on the chest. Here is more information from the Proceedings B paper:

Four-part diagram of the retinal implant system
Caption: (a,b) The subdermal [i.e., beneath the skin] coil behind the ear provides power and sends control signals via a subdermal cable and a thin intraocular [i.e., within the eye] foil to the chip in the eye. (c) The chip is placed surgically beneath the [central part of the retina] and contains 1500 pixels on a 3 mm x 3 mm area. Via a thin black cable, a small battery pack (not shown) powers the primary external coil, (d) which is magnetically kept in place above the subdermal coil behind the ear and provides power and signals via electric induction.

History of the Research

The Initial Pilot Study

Initially, a total of 11 patients received the chip device [Note: Each required a six-hour implantation surgery] in the pilot study starting in 2005, but the researchers changed the placement of the chip in the retina in an effort to improve outcomes after the first eight patients were treated. [Note: The device did not work for these initial eight patients because it was not implanted deeply enough within the eye.]

The last three patients treated were able to locate bright objects on a dark table after receiving the implant, and two of the three could name some specific objects the first time they saw them.

The Clinical Trial

Retina Implant AG’s initial clinical trial was conducted with nine subjects, from May 19, 2010 to July 28, 2011 in Tübingen, Germany. Here is more information from the Proceedings B paper:

Nine patients (four females, five males) aged 35–62 years participated in the first clinical trial. The patients received the subretinal visual implant in one eye (the one with the worst visual function). Visual function prior to implantation was light perception without correct light source localization (eight patients) or complete blindness (no light perception, one patient) caused by hereditary retinal diseases (eight patients with retinitis pigmentosa, one patient with cone-rod dystrophy). None of the subjects had other eye diseases that might affect the visual pathway.

The observation period of the subjects was three to nine months. In several patients, the observation period was limited by technical instability of the implant and was followed by the removal of the implant. Subject S8 developed post-operative subretinal bleeding in the area of the implant, and the intraocular pressure increased to 46 mmHg. This issue was resolved with topical and general medication.

In Subject S1, a touch of the optic nerve head by the tip of the implant occurred [during the surgical implantation procedure] and resulted in failure of light perception via the implant. This subject was therefore excluded from the results presented herein.

Clinical Trial Results

Excerpted from the Proceedings B paper:

In the near-vision range, the most relevant reports included the recognition of facial characteristics, such as mouth shapes (smiles) or the presence/absence of glasses, and differentiation between the contours of people and clothing patterns (striped patterns, black jacket versus white shirt).

In the far-vision range, the most frequently reported perception was finding the line of the horizon and objects along the horizon, such as houses or trees. A river was described as a bright, reflecting stripe. Cars on the street were localized on the basis of bright reflections from their surfaces; the same was true of glass windows in general.

One patient reported recognizing stopping and moving cars at night due to their headlights, as well as recognition of the course of the street according to the alignment of the streetlights. Another patient reported seeing the contours of the heads of his colleagues during a work meeting. One patient was able to read the letters of restaurant signs and store names.

When we asked our subjects about the quality of the artificial vision, they described blurred images of the world in grey tones, which is reminiscent of unfocused images from an older black-and-white television set.

The full report of clinical trial results is available at Artificial vision with wirelessly powered subretinal electronic implant in Proceedings B.

A Second Clinical Trial is Underway

On December 7, 2011, Retina Implant AG announced the initiation of the multi-center phase of the company’s second human clinical trial, which has expanded to five new European sites: Oxford, London, Budapest, and two additional locations in Germany. Unlike the first human clinical trial, this retinal implant will be permanent and patients will use the implant in real-life settings.

VisionAware will continue to provide updates of this highly anticipated research as they become available. You can also read about the Argus II, another retinal implant in development, at The Argus II Retinal Prosthesis (“Bionic Eye”) Receives Humanitarian Use FDA Approval on the VisionAware blog.

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