Argus retinal prosthesis

The Argus® II retinal prosthesis delivers a useful form of artificial vision to people with no usable vision due to severe to profound retinitis pigmentosa (RP). The device functions in place of lost photoreceptor cells and sends imperceptible electrical pulses to remaining viable retinal cells to induce visual perception. The Argus II retinal prosthesis is the standard of care for patients with severe RP and is presently the only commercially available device for retinitis pigmentosa in the U.S. It is available at more than 50 leading medical centers in North America, Europe, the Middle East and Asia.

The Argus II is manufactured by Second Sight Medical Products. The Argus II was approved for marketing in the European Union in March 2011, and it was approved by the FDA in the US in February 2013 under a [device exemption]. The Argus II has been implanted in approximately 300 patients worldwide, with proven durability beyond 10 years. Many Medicare and Medicaid and private payers provide reimbursement coverage across the majority of North America.

Clinical Application

To date, approximately 300 individuals with profound RP have been implanted with the Argus II.

Each Argus user is unique—and as a result, the level of benefit that each patient receives depends on several factors. The Argus II will not restore natural vision; rather, it provides users with a useful form of artificial vision that may enhance quality of life.

With the Argus II system, patients have been able to gain some independence as they are able to orient themselves and navigate in foreign environments. When the Argus II is used along with a cane or guide dog, it can increase independent orientation and mobility. Argus users say they have been able to: • Identify paved walkways • Perceive where the sidewalks ends • Detect doorway entrances and windows • See porch lights • Sort laundry • Differentiate between low and high contrast objects and edges • Independently navigate less familiar environments • See their dinner plate, the moon at night, fireworks, Christmas tree lights • Know when someone has left the table or room • Feel more comfortable in social settings, identify family members

The Argus® II system is the only FDA approved retinal prosthesis and is intended for use in blind individuals who meet the following criteria:

• Diagnosed with retinitis pigmentosa (RP)
• Adults, age 25 years or older
• Visual acuity in the worse affected eye of bare light perception or worse
• Previous history of useful form of vision

The Argus II is intended to be implanted in a single eye, typically the worse-seeing eye. Additionally, individuals who are considering the Argus II, must be willing and able to participate in the recommended post-implant clinical follow-up, device fitting, and visual rehabilitation.

CONTRAINDICATIONS

• Ocular diseases or conditions that could prevent the Argus II System from working (e.g. optic nerve disease, central retinal artery or vein occlusion, history of retinal detachment, trauma, severe strabismus, etc.).
• Ocular structures or conditions that could prevent the successful implantation of the Argus II Implant or adequate healing from surgery (e.g. extremely thin conjunctiva, axial length 26 mm, corneal ulcers, etc.).
• Ocular diseases or conditions (other than cataracts) that prevent adequate visualization of the inner structures of the eye (e.g. corneal opacity, etc.).
• Inability to tolerate general anesthesia or the recommended antibiotic and steroid regimen associated with the implantation surgery.
• Metallic or active implantable device(s) (e.g. cochlear implant) in the head.
• Any disease or condition (e.g. significant cognitive decline, etc.) that prevents understanding or communication of informed consent, fitting of the Argus II System, or post-operative follow-up. A pre-operative psychological evaluation may be recommended to confirm the patient is not contraindicated based on this criterion.
• Predisposition to eye rubbing.

The Argus® II is the standard of care for patients with severe RP. To date, Argus II has been implanted in over 300 patients worldwide across more than 25 exclusive regional centers. These include some of America’s most prestigious and highly regarding academic institutions including:

• Cole Eye at Cleveland Clinic
• University of Minnesota
• Mayo Clinic
• Bascom Palmer Eye
• USC Keck Eye
• Wills Eye
• Wilmer Eye at Johns Hopkins
• Kellogg Eye at University of Michigan
• Duke Medical Center
• Memorial Hermann in Houston
• University of Florida
• Tufts Medical Center
• University of Rochester Medical Center
• Stony Brook Medical Center

Additional centers are being established in order to make Argus II available across North America.

The Argus II is specifically designed to treat people with retinitis pigmentosa. The device was approved with data from a single-arm clinical trial that enrolled thirty people with severe retinitis pigmentosa; the longest follow-up on a trial subject was 38.3 months. People in the trial received the implant in only one eye and tests were conducted with the device switched on, or switched off as a control. With the device switched on, about 23% of the subjects had improvements in their ability to see; all had been at 2.9 or higher on the LogMAR scale and improvements ranged from just under 2.9 to 1.6 LogMAR – the equivalent of 20/1262 reading ability. 96% of the subjects were better able to identify a white square on a black computer screen; 57% were more able to determine the direction in which a white bar moved across a black computer screen. With the device switched on, about 60% were able to accurately walk to a door that was 20 feet away, as opposed to only 5% with the device switched off; 93% had no change in their perception of light.

Surgical procedure and data

The Argus II prosthesis is implanted via surgical procedure, under general anaesthesia. The surgery usually lasts approximately three hours. The first part of the surgery involves placing a silicone band called a “scleral buckle” around the outside of the eye (the sclera, or the white of the eye) to hold the implant in place. In the second part of the surgery, a small silicone tab (about the size of a lady bug) called the Array, is inserted inside the eye and is attached to the back of the retina. Once the implant is secured to the eye, the surgery is complete.

The implant is not visible to others and is not felt by the user, once healing is complete. After four weeks of healing, the patient sees the physician to have the system turned on and calibrated.

Among the thirty subjects in the clinical trial, there were nine serious adverse events recorded, including lower than normal intraocular pressure, erosion of the conjunctiva, reopening of the surgical wound, inflammation inside the eye, and retinal detachments. There is also a risk of bacterial infection from the implanted cables that connect the implant to the signal processor.

In 2018, at the annual meeting of the American Society of Retinal Specialists, Dr. Aleksandra V. Rachitskaya of Cleveland Clinic presented data on Argus II Retinal Prosthesis Complication Profile Pre- and Post-FDA Approval. The objective of the comparative study was to examine the complication profile of Argus II retinal prosthesis surgery before and after FDA approval. As Dr. Rachitskaya notes: Retinal prostheses are becoming more widespread in the U.S. and internationally. Over 250 Argus II retinal prosthesis surgeries have been performed worldwide. Understanding the complication profile is essential as more practitioners are implanting the device. The current study examines the serious adverse events seen in the pre-approval Argus II clinical trial and in the post-FDA approval cohort. Methods: The Argus II clinical trial was a prospective, single-arm, nonrandomized study of 30 patients, the results of which led to the FDA approval of the device. The Argus II post-approval study is an ongoing 5 year prospective post-market surveillance study which began following FDA approval. To date, there are 54 patients enrolled. The type and incidence of serious adverse events (SAEs) in the two studies was compared at 1 and 2 year marks. The study concluded: The complication profile remains acceptable up to 2 years post-operatively as site diversity increases and more surgeons implant the Argus II post-FDA approval. The changes in surgical technique such as adding the use of pericardium allografts to cover the suture tabs appear to decrease some complications. Vitreous hemorrhage appears to be more common in the post-approval study cohort.

Additionally, in November 2018, a study was published in Retina, the Journal of retinal and vitreous diseases, to analyze and provide an overview of the incidence, management, and prevention of conjunctival erosion in Argus II clinical trial subjects and post-approval patients. Methods: This retrospective analysis followed the results of 274 patients treated with the Argus II Retinal Prosthesis System between June 2007 and November 2017, including 30 subjects from the US and European clinical trials, and 244 patients in the postapproval phase. Results were gathered for incidence of a serious adverse event, incidence of conjunctival erosion, occurrence sites, rates of erosion, and erosion timing. Results: Overall, 60% of subjects in the clinical trial subjects versus 83% of patients in the postapproval phase did not experience device- or surgery-related serious adverse events. In the postapproval phase, conjunctival erosion had an incidence rate of 6.2% over 5 years and 11 months. In 55% of conjunctival erosion cases, erosion occurred in the inferotemporal quadrant, 25% in the superotemporal quadrant, and 20% in both. Sixty percent of the erosion events occurred in the first 15 months after implantation, and 85% within the first 2.5 years. Dr. Stanislao Rizzo et.al. conclude that reducing occurrence of conjunctival erosion in patients with the Argus II Retinal Prosthesis requires identification and minimization of risk factors before and during implantation. Implementing inverted sutures at the implant tabs, use of graft material at these locations as well as Mersilene rather than nylon sutures, and accurate Tenon's and conjunctiva closure are recommended for consideration in all patients.

Device functionality

The Argus II is intended to provide electrical stimulation of the retina to induce visual perception in blind individuals. The Argus retinal implant consists of a 60-electrode array that is placed on the surface of the retina. The Argus II bypasses the retina’s damaged photoreceptors. A tiny video camera mounted on special eyeglasses captures a scene. The video is electronically relayed through a small computer called a video processing unit (VPU) that processes these images, creating instructions that are sent back to the glasses. These instructions are then sent wirelessly to the implant and on to the electrode array on the retina, which emits small pulses of electricity. The array’s electrodes are activated according to the pattern of the visual image they receive from the camera. The electrodes on the implant react to the camera image and produce dots of light (called pixels) which together can be interpreted by the brain as a visual image. These pulses stimulate the retina’s remaining cells, which transmit the visual information along the optic nerve to the brain. This process creates the perception of patterns of light which, with practice, the user learns to interpret as visual patterns.

The Argus 2s, the next generation device currently in development, will deliver additional benefits of improved eyewear for better comfort and aesthetics; stronger processing power; advanced camera technology; and integration with related vision-enhancing technologies To date, approximately 300 individuals have the Argus II retinal prosthesis. Individuals with Argus® II have reported the following: • a better quality of life with greater independence and mobility • enhanced social and family interactions • greater enjoyment of aesthetic imagery and entertainment • an enhanced ability for some to return to work or re-engage in treasured hobbies • often a reduced burden on caregivers

History

The implant's manufacturer, Second Sight Medical Products, was founded in Sylmar, California, in 1998, by Alfred Mann, Samuel Williams, and Gunnar Bjorg. Williams, an investor in a cochlear implant company operated by Mann, approached Mann about founding a company to develop a similar product for the eye, and Mann called a meeting with the two of them and Robert Greenberg, who worked at Mann's foundation. Greenberg had previously worked on retinal prosthetics as a graduate student at Johns Hopkins University, and was appointed as CEO of the new company when it was launched. The first version of the prosthesis, the Argus I, was clinically tested on six people starting in 2002. The second version, the Argus II, was designed to be smaller and easier to implant, and was co-invented by Mark Humayun of the USC Eye Institute, who had been involved in the clinical testing of the Argus I. The Argus II was first tested in Mexico in 2006, and then a 30-person clinical trial was conducted in 10 medical centers across Europe and the United States.

Will McGuire joined Second Sight in August 2015 as President and CEO. The Company launched a feasibility study of its Orion I Cortical Stimulation Prosthesis to treat blindness caused by a wide range of disease including glaucoma, diabetic retinopathy, optic nerve disease and trauma. The 6-patient study is being conducted at Ronald Reagan UCLA Medical Center in Los Angeles and Baylor College of Medicine in Houston.

Society and culture

Regulatory status

The Argus II received approval for commercial use in the European Union in March 2011. In February 2013, the FDA approved the Argus II under a humanitarian device exemption, authorizing its use for up to 4,000 people in the US per year.

Pricing and Insurance coverage

The Argus® II system is presently reimbursed through a majority of Medicare carriers and private payers across North America. Full coverage is expected in 2019. Depending on the specific insurance plan, complete or partial cost of the Argus II implant surgery might be covered. The approximate cost of the Argus II is around $150,000 excluding the cost of surgery and usage training.

It was announced in November 2018, that the Centers for Medicare & Medicaid Services (CMS) finalized its Medicare hospital outpatient payment rate of $152,500 for the Argus® II Retinal Prosthesis System (Argus II) and the associated surgical implantation procedure for calendar year 2019.

Research

A trial in England funded by NHS England for ten patients began in 2017.

External links

• http://www.secondsight.com/