Retina Implant AG is developing a retinal implant with which a great number of blind patients should be able to at least partially regain their sight. The German Ministry of Education and Research (BMBF) has supported the research consortium responsible for the development of the subretinal implant so far, of which Retina Implant represents an offshoot.
At the heart of the implant lies a microchip of roughly 3 mm diameter and 50 µm thickness, in which roughly 1,500 pixel arrays are arranged. The size of a pixel is roughly 70 x 70 µm². Thus it is possible to obtain a visual field of 12°, enabling a patient to regain his or her mobility and object recognition in space. To each pixel array correspond two photocells, one amplifying circuit and one stimulating electrode. Each photocell absorbs the light falling into the eye and transforms it into electrical energy. This energy serves to control the external source energy necessary to stimulate the intact retinal nerve cells. The nervous impuses of these cells are transmitted via the optic nerve into the visual cortex where they finally produce visual images.
The chip gets implanted beneath the retina.
back to topWhere is the implanted chip located exactly?
The following diagram illustrates the location of the implant in the eye:
The implant is placed directly where in the retina in a normal sighted person the light-sensitive photoreceptor cells are located. This guarantees that the electric impulses emitted by the implant are actually transmitted to the same retinal nerve cells that in persons with healthy retinas receive information from the photoreceptors. The information processing network of the retina is used in the normal, “natural” fashion.
back to topEnergy supply of the implant
In order to be able to overcome the stimulus thresholds for a successful stimulationof the retinal nerve cells, it is necessary to provide a signal amplifier that is integrated in the chip. Without amplifier, no visual image would be possible with ordinary daylight. The necessary energy will be provided via fine wires from the outside for the first clinical trial series. High-frequency energy will be used for the second clinical trial series that should run for a period of 6 months.
The parts are mounted on a highly flexible polyimid-ribbon. With the exception of the stimulating chip, the entire implant is embedded in silicon.The length of the implant measures roughly 20 mm, the width 3 mm and the thickness between 0.1mm and 0.5 mm. Only the right half of the implant will be pushed beneath the retina; the left, thicker half will be sewn onto the eyebulb and covered by the conjunctiva.
back to topWhat results can be obtained with the help of the chip?
Even a spatial resolution of 1° visual angle entails a significant improvement of the patient’s quatlity of life since it allows for orientation in rooms, recognition of larger objects and of faces.
In short, after implantation of the subretinal chip the patient’s sight should fulfill the following criteria:
- Orientation in space
- visual field: 8° - 12°
- ability to read without visual aids (except for reading glasses): at the least being able to count fingers of another person’s hand, ideally being able to recognize faces
- ability to recognize letters with additional visual aids
- ability to function in surround brightness of 10 Lux to 100.000 Lux.