Argus II, an artificial retina device is being using mainly with RP (retinitis pigmentosa) patients for now.  RP causes night blindness with peripheral vision issues.  Many RP patients have tunnel vision or are completely blind.  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 is designed to bypass the damaged photoreceptors altogether.  A retinal surgeon attaches an electrode array to the eye that receives signals from a pair of glasses worn by the patient that are equipped with a video camera. Think of it as a bionic eye. The camera captures video footage and transmits the images as series of electrical pulses to the eye that the brain then perceives as visual images.  Patients who were unable to see anything before using the Argus II are able to detect shapes and pick up contrast between light and dark. Someone who is blind can have more mobility, orientation and a connection to their surroundings. They can see fireworks explode.
More than 170 patients have been equipped with the Argus II in the United States so far. The FDA approved it in 2013. Second Sight had been selling it for $143,000 — although Medicare will now reimburse up to $95,000 for the implant and surgery.
Second Sight, like many young healthcare companies, is losing money and spending a lot on research and development.
sources:  money.cnn.com; secondsight.com