What Is A Retinal Prosthesis?

A retinal prosthesis is a biomedical implant intended to partially restore useful vision to people who have lost their sight due to a degenerative retinal disease such as retinitis pigmentosa (RP) that severely damages the photoreceptors in the eye.

 

 

What Is The Argus® II Retinal Prosthesis System?

The Argus II Retinal Prosthesis System (“Argus II”) is intended to provide electrical stimulation of the retina to induce visual perception in blind individuals.

In a healthy eye, the photoreceptors (rods and cones) in 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 (RP)—the first step in this process is disrupted, and the visual system cannot transform light into images.

Argus II bypasses 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 an antenna in the implant. The signals are then sent to the electrode array, which emits small pulses of electricity. These pulses bypass the damaged photoreceptors and stimulate the retina’s remaining cells, which transmit the visual information along the optic nerve to the brain, creating the perception of patterns of light. Patients learn to interpret these visual patterns.

For more information on how Argus II produces sight: details

 

 

Who Might Benefit?

Argus II currently provides some useful vision to patients with severe to profound vision loss due to outer retinal degeneration, such as retinitis pigmentosa (RP) .

Argus II is approved for use in the European Economic Area (CE Mark) for persons meeting the following criteria:

 

  • Adults, age 25 years or older
  • Severe to profound outer retinal degeneration
  • Some residual light perception; if no residual light perception remains, the retina must be able to respond to electrical stimulation
  • Previous history of useful form vision

Additional exclusion criteria may apply. Consult your physician.

 

What Do You See With Argus II?

Argus II restores “vision” that is not the same as the natural vision experienced by the patient prior to blindness. It may best be described as “somewhat pixelized” vision composed of spots of light which, in an ideal case, cover the central 20° visual field. This can be compared to a 30 cm ruler held out at arm’s length.

 

Typically, time is required to learn to interpret the images produced by the system and results are variable between patients. Some patients are able to easily discern forms, identify large written characters, and locate light sources, while others are not able to interpret spatial information about the visual scene with their system. In the study, patients were consistently better at performing orientation and mobility tasks using Argus II.

Some activities* performed by patients who participated in the clinical study were:

  • Locating or identifying objects
    • Finding utensils on a table
    • Locating parked & moving cars
    • Locating bus stop poles & flag poles
  • Orientation and mobility
    • Finding doors, windows, elevators
    • Following a sidewalk or curb
    • Following a crosswalk across a street
  • Detecting light
    • Locating an overhead light in an entranceway
    • Locating a window by incoming light
  • Household tasks
    • Sorting light & dark coloured laundry
  • Identifying large letters & numbers
  • Reading large print words

*NOTE: not all patients could perform all of these tasks

 

Is A Surgical Procedure Required?

Yes, a surgical procedure is used to implant Argus II. The surgery can typically be completed within 4 hours and requires general anaesthesia. A one-night hospital stay may be required. Pre- and post-operative medication will be defined as necessary by the physician. Support from family or friends is recommended (but not required) for the post-operative follow-up.

 

 

Are There Any Risks?

As with any surgical procedure or implanted device, there are risks. Please consult your physician directly.

 

 

What Happens After Surgery?

Following implantation surgery, patients return to the clinic several times over the next few months for medical follow-up, to have their system customized, and to receive training on how to use the system. Once this fitting and training is completed, the patients may begin to use the device at home. At this point, patients may elect to receive rehabilitation sessions conducted by a low-vision therapist. These sessions are intended to teach patients how to interpret and use their new visual skills in their daily lives.

 

 

How Do I Learn More?

For more information about the system: Argus II
Patient information brochure:download
For any other questions, please consult your physician directly or send a message to Second Sight: patients@2-sight.com.