gms | German Medical Science

Artificial Vision — The 2nd Bonn Dialogue. The International Symposium on Visual Prosthesis

Retina Implant Foundation

19.09.2009, Bonn

The IMI Trials

Meeting Abstract

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Artificial Vision – The 2nd Bonn Dialogue. The International Symposium on Visual Prosthesis. Bonn, 19.-19.09.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ri18

doi: 10.3205/09ri18, urn:nbn:de:0183-09ri189

Veröffentlicht: 30. November 2009

© 2009 Hornig et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen ( Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.



The “Intelligent Retinal Implant System” (IRISTM) has been developed with the aim of providing modest visual perception to blind patients suffering from retinal degeneration e.g. retinitis pigmentosa.

This epi-retinal prosthesis consists of an implantable part and two external parts. The implantable part is called the Retina Stimulator and is provided with energy wirelessly. The external components are the Visual Interface (VI) and the Pocket Processor (PP). The VI resembles a pair of sunglasses. A tiny camera is integrated within the Visual Interface to capture images from the patients’ surrounding and convert the image information into electronic signals. These signals are sent via a thin cable to the walkman sized Pocket Processor.. The PP processes the data and converts them into stimulation commands using very adaptable algorithms. The processed signals are then sent back via cable to the Visual Interface, where the signals are sent wirelessly to the implanted retina stimulator. The Retina Stimulator receives the data and generates the stimulation currents to activate the nerve cells of the retina. The stimulation currents are applied by an electrode array, which is placed epi-retinally onto the macular.

The implant is specially designed to allow ease of explants and potential replacement thereby allowing potentially allowing patients to benefit from future refinements in the technology. It is coated with a special surface material, which is biocompatible and does not adhere to the retinal tissue. Furthermore the implant is fixed with a special system that allows the removal of the Retina Stimulator with low risk of retinal detachment.

A preliminary clinical trial revaluated the electrode array, which was implanted into humans during vitreoretinal surgeries. The retina was stimulated for maximum 45 minutes using a cable connected current source. The trial provided information relating to the optimum amount of current and electrode size.

The next step was a chronic study of prototype retinal stimulators. Selected patients from the first trial with low stimulation thresholds were enrolled. The Retina Stimulator was implanted into one eye and activated during several stimulation sessions. In this trial no camera was used. Stimulation signals were generated by a connected computer. Patients were able to localize phosphenes and to differentiate between different stimulation patterns.

In a further clinical trial an advanced system was used. In this trial the camera was used for the first time. Patients used the system in a series of stimulation sessions in the clinic. For the first time vision training was introduced in the Retina Implant treatment. This training proved to be critical and subsequently a patient could localize and grasp a ball.

IMI and the participating clinical sites are currently recruiting for the next step of clinical programme. The main objectives of the latest trial is to assess the real benefit of the device in the everyday life of patients and therefore patients will be encouraged to use the system in their normal daily surroundings.