An Update on Prosthetic Vision

The Argus II is one of a variety of implanted electrode grid devices under development that supply a substitute for vision in the blind by stimulating the retina to produce phosphene patterns. Per this latest news, the device continues to progress much as expected in the clinical trial system. Most users in the latest small trial of several years benefited from the implant, and there were no device failures. Ultimately it might be expected that the research into retinal and optic nerve stimulation that produced the Argus systems will result in something closer to real vision. That, however, will require quite different and more sophisticated approaches than used at present, a process of development that has barely started, and for many types of blindness it may be overtaken by advances in retinal regeneration. It remains to be seen whether prosthetic technologies or regenerative medicine dominate in the years ahead for the alleviation of various types of damage that cause blindness:

Retinitis pigmentosa is an incurable disease that causes slow vision loss that eventually leads to blindness. The Argus II system was designed to help provide patients who have lost their sight due to the disease with some useful vision. Through the device, patients with retinitis pigmentosa are able to see patterns of light that the brain learns to interpret as an image. The system uses a miniature video camera stored in the patient's glasses to send visual information to a small computerized video processing unit which can be stored in a pocket. This computer turns the image to electronic signals that are sent wirelessly to an electronic device implanted on the retina, the layer of light-sensing cells lining the back of the eye.

The Argus II received Food and Drug Administration (FDA) approval as a Humanitarian Use Device (HUD) in 2013, which is an approval specifically for devices intended to benefit small populations and/or rare conditions. To further evaluate the safety, reliability and benefit of the device, a clinical trial of 30 people, aged 28 to 77, was conducted in the United States and Europe. All of the study participants had little or no light perception in both eyes. The researchers conducted visual function tests using both a computer screen and real-world conditions, including finding and touching a door and identifying and following a line on the ground. A Functional Low-vision Observer Rated Assessment (FLORA) was also performed by independent visual rehabilitation experts at the request of the FDA to assess the impact of the Argus II system on the subjects' everyday lives, including extensive interviews and tasks performed around the home.

The visual function results indicated that up to 89 percent of the subjects performed significantly better with the device. The FLORA found that among the subjects, 80 percent received benefit from the system when considering both functional vision and patient-reported quality of life, and no subjects were affected negatively. After one year, two-thirds of the subjects had not experienced device- or surgery-related serious adverse events. After three years, there were no device failures. Throughout the three years, 11 subjects experienced serious adverse events, most of which occurred soon after implantation and were successfully treated. One of these treatments, however, was to remove the device due to recurring erosion after the suture tab on the device became damaged.

Link: http://www.eurekalert.org/pub_releases/2015-06/aaoo-bec062315.php

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