Prof. Eberhart Zrenner, Universitäts-Augenklinik Tübingen, Leiter des Forschungsprojekts Subretinales Implantat spricht mit Projekt Zukunft über die neuen Augenprothesen.
DW: I want to know why you have taken the implant back out again from Mika, the Finnish test patient?
Eberhart Zrenner: That was of course a very difficult decision, but on the other hand, this was the first series of patients, where a cable still came out of the head behind the ear. Because it was a proof of principle, and that's why we had to remove it. The patient knew that ahead of time. Now we have patients that have it all in the body. And they can have it continuously.
There are many types of blindness as well. Who are you targeting with this particular retina chip?
We are really replacing the lost natural photoreceptors with technical photoreceptors. Like solar cells, with amplifiers behind, and so we need an intact optic nerve and we need an intact inner retina. So people with diabetic retinopathy or glaucoma would not be suited for this approach.
So the optical nerve has to be intact?
Yes, it must be intact.
And there's of course black-and-white they're seeing as well. Do you think you're going to be able to improve on this in the next phase of your studies?
Well, we will improve on contrast and sharpness of image, but I don't think we will ever go to color so easily, because it's just too complicated. But as everybody knows, black-and-white football matches are as nice as a color one is, aren't they?
Yes, people definitely look better in black-and-white! Now it's been a long road -- 16 years working on this chip -- how did it actually feel when the first patient started to describe his surroundings to you?
It was amazing. We sat there speechless for a few seconds, because the patient read this word -- his name. We weren't sure for a moment whether he had estimated it or really read it, then he said 'You have written it incorrectly. There's a second 'i' in my name." So we knew that he had seen it perfectly, and the lab burst out with joy of course.
Absolutely amazing, and really emotional, I'm sure.
Yes, it was!
What about the most difficult aspects then of developing this chip and artificial retina. What would you say that is?
Well of course you have to do ten years of clinical work understanding how much current you need, how much current is too much, how to do the surgery, and how biocompatibility can be maintained of the chip in the body. And of course this is still the biggest challenge - having a long duration of the chip. Presently we can see 11 months of working with the chip, because we started the new study in 2010, and we don't know how long it will last.
And do you find that the body rejects the chip?
No. And that's surprising -- especially under the retina. There is very little reaction from the retina. We have a patient who has had it for four years now - it's not working anymore. But he kept it because he wants a new one - and the chip looks like it did in the first days.
And also I know you're looking for more test volunteers in the future for studies. Is that correct?
Yes, that's correct. We have forty more patients left to go in the clinical study. It's cost-free for patients. So we hope to have more of them who will join us in this study.
(Interview: Anne O'Donnell)