FDA Approves Argus II Retinal Prosthesis

The Food and Drug Administration (FDA) of the United States has approved the first retinal implant for use in the United States. This approval is for Second Sight’s Argus II Retinal Prosthesis System, which provides limited sight to those patients blinded by a rare genetic eye condition called advanced retinitis pigmentosa. This condition damages the light-sensitive cells that line the outer layer of the retina and causes them to die. This severely reduces vision and eventually leads to blindness.

Argus II

Second Sight has devoted more than 20 years of research and development to the development of the Argus II Retinal Prosthesis. It has succeeded in two clinical trials, and the funding for the development of this device – more than $200 million – came from the National Eye Institute, the Department of Energy and the National Science Foundation. The remaining money came from private investors. European regulators approved the Argus II for use in 2011 and it has been used in 30 patients in clinical-trial patients since 2007. The Ophthalmic Devices Advisory Panel of the FDA unanimously recommended approval for the Argus II in September 2012.

The Argus II includes a small video camera, a video processing unit and a 60-electrode implanted retinal prosthesis with a transmitter mounted on a pair of eyeglasses. This device replaces the function of degenerated cells in the retina. It must be stressed that the Argus II does not fully restore vision, but it can improve a patient’s ability to perceive images and movement. It uses the video processing unit to transform images from the video camera into electronic data that is wirelessly transmitted to the retinal prosthesis.

Retinitis pigmentosa affects about one in 4,000 people in the US and about 1.5 million people worldwide. It kills off the retina’s photoreceptors, which convert light into electrical signals that are transmitted by means of the optic nerve to the brain’s visual cortex for processing. Second Sight plans to adapt its technology to assist people afflicted with age-related macular degeneration, which is a similar but more common disease.

Second Sight has plans to make the Argus II available later this year in clinical centers throughout the US. They want to establish a network of surgeons who have the skills to implant the device and, eventually recruit hospitals to offer it.

The Argus II is not the only retinal implant under development. A medical start-up company called Retina Implant AG uses a different approach in its device. In this case, the prosthetic device, the Alpha IMS Implant, is inserted beneath a portion of the retina. The three- by three-millimeter microelectronic chip (0.1-millimeter thick) contains ~1,500 light-sensitive photodiodes, amplifiers and electrodes. The Alpha IMS Implant is surgically inserted beneath a portion of the retina known as the fovea (which contains a rich concentration of particular photoreceptors known as cone cells) in the retina’s macula region. The fovea enables the highest clarity of vision for people to read, watch TV and drive. This chip helps generate at least partial vision by stimulating intact nerve cells in the retina. The nerve impulses from these cells are then fed by means of the optic nerve to the visual cortex where they create impressions of sight. The power source for the chip is implanted under the skin behind the ear and connected by a thin cable to the chip. In May the company announced its first UK patients for its latest trial. To date surgeons have implanted the Alpha IMS Implant prosthetic in 36 patients through two clinical trials over six years.

Alpha IMS Implant

Researchers from Stanford University researchers are developing self-powered retinal implants in which each pixel in the device is fitted with silicon photodiodes. These sensors detect light, and control the output of a pulsed electric current. Patients would be required to wear a set of goggles for these devices that emit near-infrared pulses that transmit power and data directly to the photodiodes. Inductive coils that must be surgically implanted in the patient’s head to power these other retinal prostheses. This design was reported in May 2012 issue of Nature Photonics, and in the article, they described in vitro electrical stimulation of healthy and degenerate rat retina by photodiodes powered by near-infrared light.

Other researchers are utilizing yet another design for retinal prosthesis design. Researchers from Weill Cornell Medical College in New York City have deciphered the neural codes that mouse and monkey retinas use to turn light patterns into patterns of electrical pulses that their brains translate into meaningful images. Next they programmed this information into an “encoder” chip that was combined with a mini-projector to create an implantable prosthetic. This chip converts images that come into the eye into a series of electrical impulses, and the mini-projector then converts the electrical impulses into light impulses that are sent to the brain. With this approach, instead of increasing the number of electrodes placed in an eye to capture more information and send signals to the brain, this approach increases the quality of the artificial signals themselves, which improves their ability to carry impulses to the brain.

StemCells Inc. Announces the Commencement of Their Macular Degeneration Clinical Trial

Age-related macular degeneration or AMD is a disease of the retina (at the back of the eye) characterized by a loss of photoreceptors (rods and cones) from the central part of the retina (macula), where vision in the clearest. A degenerative retinal disease, AMD typically strikes adults in their 50s or early 60s, and insidiously progresses usually painlessly until it gradually destroys central vision. There are approximately 1.75 million Americans age 40 years and older with some form of AMD, and the disease continues to be the number one cause of irreversible vision loss among senior citizens in the United States with more than seven million at risk of developing AMD.

There are no cures for AMD, but laser treatments are available for some types of AMD. Laser photocoagulation can disperse fluid that has built up under the retina. Such AMD is called “wet” macular degeneration and only works in the treatment of 15/100 cases of AMD. Other treatments include injections of either Avastin, Macugen or Eylea into the eye to prevent the spread of blood vessels that crowd out photoreceptors.  Photodynamic therapy uses a drug called Visudyne that is injected into the arm and them activated by a laser one in the eye where it destroys meandering blood vessels that leak or proliferate across the retina.  Patients with “dry” macular degeneration, however, find themselves out of luck.

Into the breach comes a clinical study by StemCells Inc. to use their proprietary neural stem cell line to treat dry macular degeneration. This Phase I/II clinical trial has already enrolled and transplanted its first patient this week and more subjects will undoubtedly be enrolled later. This trial is designed to evaluate the safety and preliminary efficacy of StemCells Inc’s proprietary HuCNS-SC neural stem cell line as a treatment for dry AMD. The first patient in this clinical trial received their transplant at the Retina Foundation of the Southwest in Dallas, Texas, which is one of the leading independent vision research centers in the United States. Globally, AMD afflicts approximately 30 million people worldwide and is the leading cause of vision loss and blindness in people over 55 years of age.

In February 2012, StemCells Inc Company published preclinical data that clearly showed that HuCNS-SC cells protect host photoreceptors and preserve vision in the rats that are engineered to experience retinal degeneration. This rat strain (Royal College of Surgeons or RCS rats) are a very well-established animal model for retinal disease and has been used extensively to evaluate potential cell therapies. In these pre-clinical studies, the number of cone photoreceptors, which are responsible for central vision, did not decrease due to cell death, but instead remained constant over an extended period. These same rats that had HuCNS-SC cells transplanted into their retinas showed steady maintenance of their visual acuity and light sensitivity. In humans, degeneration of the cone photoreceptors accounts for the unique pattern of vision loss in dry AMD. These data were published in an international peer-reviewed journal known as the European Journal of Neuroscience.

“This trial signifies an exciting extension of our on-going clinical research with neural stem cells from disorders of the brain and spinal cord to now include the eye,” said Stephen Huhn, MD, FACS, FAAP, Vice President and Head of the CNS Program at StemCells, Inc. “Studies in the relevant animal model demonstrate that the Company’s neural stem cells preserve vision in animals that would otherwise go blind and support the therapeutic potential of the cells to halt retinal degeneration. Unlike others in the field, we are looking to intervene early in the course of the disease with the goal of preserving visual function before it is lost.”

David G. Birch, Ph.D., Chief Scientific and Executive Officer of the RFSW and Director of the Rose-Silverthorne Retinal Degenerations Laboratory and principal investigator of the study, added, “We are excited to be working with Stem Cells [Inc.} on this ground breaking clinical trial. There currently are no effective treatments for dry AMD, which is the most common form of the disease, and there is a clear need to explore novel therapeutic approaches.”

Pea-Sized Telescopic Implant Restores Vision in Patient with Advanced Macular Degeneration

Eye surgeons at my alma mater, UC Davis Medical Center, have managed to successfully implant a new telescope-type implant in the eye of a patient who suffers from end-stage age-related macular degeneration (AMD). AMD is the most advanced form of the macular degeneration and is a leading cause of blindness in older Americans.

These telescope implants were approved by the Food and Drug Administration in 2010, and it is the only medical/surgical option available that can restore at least a portion of the patient’s vision. Eye doctors at the UC Davis Health System’s Eye Center collaborated with the Society for the Blind in this procedure. The UC Davis Health System’s Eye Center is one of the few medical centers in California and the whole nation to offer this innovative procedure.

Mark Mannis, professor and chair of ophthalmology and vision sciences and director of the Eye Center at UC Davis Health System, explained: “Macular degeneration damages the retina and causes a blind spot in a person’s central field of vision. The telescopic implant restores vision by projecting images onto an undamaged portion of the retina, which makes it possible for patients to again see people’s faces and the details of objects located directly in front of them.”

It is presently unclear what causes dry macular degeneration. It clearly forms as the eye ages. Macular degeneration consists of massive die offs of the cells in a particular part of the retina called the “macula.” The macula contains millions of light-sensing cells that provide sharp, detailed central vision, and it is also the most light-sensitive part of the retina. The retina quickly turns light into electrical signals and then sends these electrical signals to the brain through the optic nerve. The brain translates the electrical signals into images. If the macula is damaged, fine points in these images become unclear, fuzzy, spot-ridden, or simply black.

In May 2012, UC Davis cornea specialists Mannis and Jennifer Li implanted the miniature telescope, which is smaller than a pea, in the left eye of a macular degeneration patient names Virginia Bane, who is 89 years old and is from the California town of Pollock Pines, which is near Sacramento. Mrs.Bane is an artist who loves to paint, but has not painted for four years because her eyesight does not allow her to see well enough to do so. Mrs.Bane is the first in Northern California and among the first 50 individuals in the nation to receive this implant.

“I can see better than ever now,” Bane said. “Colors are more vibrant, beautiful and natural, and I can read large print with my glasses. I haven’t been able to read for the past seven years. I look forward to being able to paint again.”

Optometrists from the Society for the Blind and UC Davis occupational therapists have been working with Mrs. Bane to help to learn how to use her implant to its full extent.

“Virginia’s vision will keep getting better and better over time as she retrains her brain how to see. She basically uses her left eye with the telescopic implant to see details, such as using a microwave keypad and reading a book,” said Richard Van Buskirk, who works as an optometrist with the Society for the Blind in Sacramento who specializes in treating patients with low vision. “Her untreated right eye provides peripheral vision, which helps with mobility, such as walking or navigating within her home. Ultimately, her brain will automatically make the shift, using the capability of each eye as needed.”

Retina specialists from UC Davis who treat macular degeneration and other eye disorders associated with the back part of the eye coordinate the treatment program with optometrists who specialize in caring for patients with low vision. Patients are extensively screened before they can participate in this program and undergo medical, visual and functional evaluations to determine if they are good candidates for the procedure.  However, there is a simulator that can show patients what their eyesight might resemble if they were to receive the implant.  This simulator determines if the procedure will actually help the patient see better.

Most candidates for this procedure have very advanced, untreatable eye diseases and include end-stage, age-related macular degeneration (dry form).  All patients must have a disease that is stable and severely impairs vision. Candidates must also be at least 75 years old and have adequate peripheral vision in the eye that will not receive the implant and have no other ocular diseases, such as glaucoma.