Transchoroidal implant surgery for RP successful

May 9, 2012

Implantation of a new transchoroidal artificial device for patients with retinitis pigmentosa provides blind patients with visual abilities and vision that does not fade, said Helmut Sachs, MD, who described the results achieved with 20 patients.

Fort Lauderdale, FL-Implantation of a new transchoroidal artificial device for patients with retinitis pigmentosa (RP) provides blind patients with visual abilities and vision that does not fade, said Helmut Sachs, MD, who described the results achieved with 20 patients.

The subretinal implant is made of a stimulation chip with 1,500 electrodes on polyimide film. Initially, the device had a transchoroidal cable for power and signals that was used in the first patients and was replaced after 30 days with a wireless version, said Dr. Sachs, of the Eye Clinic, Klinikum Dresden Friedrichstadt, Dresden, Germany.

“The device has correct retinotopical localization,” Dr. Sachs said. “The remaining retinal cellular network is used. There are no fixation problems associated with the device. The device has highest resolution up to 1,500 pixels. Micro-saccades refresh the images, and there is no fading of vision or image instability. There is no external camera with the system and no learning curve.”

The device was implanted after conventional vitrectomy followed by creation of a subretinal bleb in the parafoveal region. In the corresponding region, the sclera is prepared down to the choroid, which is then cauterized to enable entry into the bleb from outside without bleeding. A guide foil, which prevents the soft device from rolling up into the bleb, is advanced in the macular region and the device is implanted behind the guide foil.

Following successful implantation in all patients, Dr. Sachs showed patients performing visual tasks outside of the clinic. Patients could recognize faces, read, identify objects, see objects move, and avoid obstacles. Importantly, patients achieved constant perception with no fading of vision. One patient was able to see from 30 to 60 minutes.

“Transchoroidal surgery is feasible and well tolerated by patients,” Dr. Sachs said.

No complications developed, such as retinal detachment, or major displacement of the implant, inflammation, or endophthalmitis.

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