Institute for Ophthalmic Research

Core of the implant is a microchip of approximately 3 mm in diameter and 50 μm thickness, with an array of roughly 1500 pixel fields (see Fig. 1).
Each pixel measures 70 x 70 μm. Photocells, an amplifying circuit, and a stimulation electrode are attached to each pixel field. The photocells absorb the light entering the eye, transforming it into electrical signals. A tiny power line is providing energy from an external source behind the ear. Sixteen additional electrodes are placed for testing purposes at the tip of the implant (see Fig. 1).

Figure 1 Microchip array

The strength of the light signals controls the amount of current released by each electrode, stimulating the neighboring intact retinal nerve cells electrically. The nerve impulses generated by the retinal cells are processed in the remaining neuronal network of the retina and transmitted via the optic nerve to the visual cortex, creating visual sensations. This is why an unimpaired, regularly functioning optic nerve is an unconditional requirement for the implants' operational reliability in any approach of a retinal implant.

In the first study, energy is being provided externally by a small stimulation box, placed in the patients' pocket. In future chip generations, energy will be supplied by a subcutaneous device, already a standard procedure in cochlear implants.