gms | German Medical Science

Objective: To restore visual functions by a photosensitive microchip with 1500 pixels (Alpha IMS from Retina Implant AG, Reutlingen, Germany, having received recently CE mark for commercial use in Europe).

Material and Methods: Alpha IMS implants with wireless power and signal transmission were meanwhile placed into the subretinal space of 25 patients blind from retinal dystrophy in order to restore some visual functions; brightness and contrast perception can be controlled by the patient.

Results: Here we report on the first module of the multicenter trial on experiences with implant surgery in 9 patients. All the subjects had successful implantation of the chip. All were able to perceive light after implantation of the photodiode chip. The visual experiences ranged from perception of light where there was none before surgery, to the ability to see individual letters 4 cm high at a working distance of 40 cm. Motion detection was possible up to angular speed up to 35 deg/s, grating acuity up to 3.3 cpd. In some cases visual acuity measurement with Landolt C-rings was possible up to Snellen visual acuity of 20/546. Additionally, the identification, localization and discrimination of objects improved significantly in most patients. In repeated tests over a nine month period, several subjects were able to read letters spontaneously, controlled in four alternative forced choice tests. Control tests were performed each time with the implant's power source switched off.

Discussion: The study has shown proof of concept that a photodiode chip placed in the subretinal space can provide useful vision for many subjects. Selection of patients based on experiences with preoperative OCT analysis, fluorescence angiography and autofluorescence helps to identify patients optimally suited for subretinal electronic implants.

Acknowledgement: The clinical trial (www.clinicaltrials.gov, NCT01024803) was supported by Retina Implant AG, Reutlingen, Germany