In a healthy eye, the photoreceptors (rods and cones) on the retina convert light into tiny electrochemical impulses that are sent through the optic nerve and into the brain, where they are decoded into images. If the photoreceptors no longer function correctly — due to conditions such as retinitis pigmentosa — the first step in this process is disrupted, and the visual system cannot transform light into images.
The Argus II Retinal Prosthesis System (“Argus II”) is designed to bypass the damaged photoreceptors altogether. A miniature video camera housed in the patient’s glasses captures a scene. The video is sent to a small patient-worn computer (i.e., the video processing unit – VPU) where it is processed and transformed into instructions that are sent back to the glasses via a cable. These instructions are transmitted wirelessly to a receiver in the implant. The signals are then sent to the electrode array, which emits small pulses of electricity. These pulses are intended to bypass the damaged photoreceptors and stimulate the retina’s remaining cells, which transmit the visual information along the optic nerve to the brain. This process is intended to create the perception of patterns of light, which patients can learn to interpret as visual patterns.
The device is an epiretinal prosthesis surgically implanted in the eye that includes a receiving coil, an electronics case, and an electrode array. The external equipment consists of glasses, a video processing unit (VPU), and a cable.
Thirty patients participated in the clinical trial, using the device at home and in their daily lives since the trial started. Although the resulting vision is far from normal, investigators in the clinical trial of the Argus II have reported positive results. In trials at Moorfields Eye Hospital in London, the majority of patients exhibited the ability to recognize large letters and locate the position of objects.
With its CE Mark approval, the Argus II is scheduled to be available later this year in the following clinical centers: Centre Hospitalier National d’Ophthalmologie des Quinze-Vingts (Paris, France), Hôpitaux Universitaires de Genève (Geneva, Switzerland), Manchester Royal Eye Hospital (Manchester, UK), and Moorfields Eye Hospital, (London, UK). Second Sight is actively adding sites to make the therapy more readily available across the EEA in the coming months and years.
This technology was done by Second Sight Medical Products, Sylmar, CA. For more information, visit http://info.hotims.com/34455-167.