Retinal Implant Brings Some Sight To Profound Retinitis Pigmentosa Patients

The Six Million Dollar Man had superhuman eyesight, but insurers won’t have to pay that much for this treatment

Thomas Morrow, MD

I have highlighted science fiction movies and television shows in the past because so many advances in medicine were predicted by Hollywood. One of my favorites as a new physician was The Six Million Dollar Man, a five-year TV series that started in 1973 and starred Lee Majors. It was based on the novel Cyborg, written by Martin Caidin and published in 1972.

Steve Austin, the main character, played an astronaut who, after an accident, was given artificial limbs that provided superhuman strength and speed. In addition, he was given a new electronic eye. Now fast-forward four decades. The FDA in February approved the Argus II Retinal Prosthesis System, developed by Second Sight “to provide electrical stimulation of the retina to induce visual perception in blind patients.”

It is indicated for use in patients with severe to profound retinitis pigmentosa, which results in visual loss at very early ages. It is part of a family of genetic diseases with a dominant inheritance pattern.

Unfortunately, there are literally hundreds of genetic variations in several genes — the majority of which involve the proteins opsin and rhodopsin.

The condition is characterized by progressive loss of photoreceptor cells. Although numerous therapeutic approaches have been tried, there is no cure.

Argus II

The Argus II study enrolled patients who met the following criteria:

  • Age 25 years or older
  • Bare light or no light perception in both eyes (if patient has no residual light perception, then evidence of intact inner layer retina function must be confirmed.)
  • Previous history of useful form vision
  • Aphakic or pseudophakic (if the patient is phakic prior to implant, the natural lens will be removed during the implant procedure.)
  • Patients who are willing and able to receive the recommended post-implant clinical follow-up, device fitting, and visual rehabilitation

The Argus II implant is not intended to be used bilaterally. It is intended to be implanted in the worse eye.

There are a number of contraindications, including some that could prevent the system from working, such as optic nerve disease, central retinal artery or vein occlusion, retinal detachment, trauma, and severe strabismus. Also, corneal opacity can prevent the visualization of the inner structure and is a contraindication.

Any metallic or active implanted device in the head, such as a cochlear implant or CNS stimulator, is also a contraindication.

After implantation, patients will have permanent restrictions on the use of certain types of MRI, laser, electroshock, and other electromagnetic and ultrasound procedures. Even eye rubbing can cause problems with these patients.

Complex system

The Argus II system has of a number of parts.

The main component is the retinal prosthesis that is located partially outside and partially inside the eye, with a band-like device that encircles the eye. This component provides the electrical stimulation to the retina and consists of four subcomponents:

  • A small electronic package that receives power to drive the electrical stimulation of the implanted electrodes.
  • A coil that receives and transmits data to and from the external primary coil located on the glasses.
  • A thin-film electrode cable that is connected to the package and transmits the stimulation signals to the retina via 60 exposed platinum electrodes.
  • A scleral band that allows the implant to be secured to the outside of the eye.

There are two external subsystems. The first is a video camera mounted above the nosepiece in the center of a pair of “glasses.”

The glasses are nonfunctional in the usual sense, but are cosmetic and hold the camera. The telemetry coils and radio-frequency system are mounted on one of the arms of the glasses.

The second subsystem is the video processing unit (VPU), a battery-powered device, worn by the patient in a pouch, that processes the data from the video camera and sends it back to the eye.

Some very specialized surgical tools and computer programs must be acquired to successfully implant and program the device.

The clinical trial to determine safety and probable benefit of the Argus II system is different from most, to say the least. It was a nonrandomized, single-arm study where the subjects became their own control based on the system being turned on and off.

Clinical trial

It included 30 subjects in 10 centers, both in the United States and in Europe. All were functionally blind with bare light perception at the beginning of the study. Most of the subjects’ vision had reached this point by their mid-30s. The mean age of the participants was 58 years and the mean time from the time of functional blindness until enrollment in the study was 17.5 years; hence, virtually all of the subjects had adapted to blindness. Enrollment began in June 2007. As of the FDA filing, subjects had been implanted for about two and a half years but some for as long as four years.

Remarkably, for a procedure that involves an extra-ocular and an intra-ocular device, there were few adverse events. The earliest patients implanted have accumulated four years of follow-up. Nineteen subjects experienced minor or no adverse events and were treated with routine ocular medication(s) or observation only. Seven others experienced adverse events that resolved with minor interventions or topical therapy. The remaining four had a distinctly different course and accounted for over half of all of the serious adverse events. One subject — the only one explanted — had to have the implant removed at 14 months because of conjunctival erosion. Most of the adverse events occurred in the first six months after implant.

Nine subjects required surgical intervention to reposition the implant or retack it in place. One device failed at four years but remained implanted.

All 30 subjects had some visual perception after the Argus II was activated. The majority had improvement that ranged from light perception to hand motion perception to counting fingers. Some had a renewed perception of color and a few even recognized large letters and could locate objects.

Managed care implications

The cost of the Argus System and the surgical implantation and follow-up has been estimated to be around $115,000. The cost of the device is the largest single component and is affected by hospital contracts, so a specific cost is impossible to predict for a given health plan. The typical health plan will encounter very few patients, partially because of the rare occurrence of the condition but also because the implantation requires quite a bit of post-operation care. This is the only treatment available to a functionally blind patient with retinitis pigmentosa and will probably be covered by most insurers.

Thomas Morrow, MD, is the immediate past president of the National Association of Managed Care Physicians. He has 24 years of managed care experience at the payer or health plan level. Contact him at [email protected].

The author is a director in the value-based health department at Genentech. He has had no other industry affiliations in the past three years. The views expressed in Tomorrow’s Medicine are the author’s alone.