Until recently, technology still lacked the ability to truly connect machines directly to a nerve.  They merely detected or sent electrical impulses through tissue rather then making a physical connection.  However, advances now allow a small piece of silicon to be attached to a neuron as a transmitter.  Current research is utilizing this technology to develop retinal and cortical stimulation where light is converted to electrical signals, which are directly connected to nerve cells and sent to the brain.

Great, What Is It Good For?
While bionics has already opened the door for replacing lenses and corneas, it still is focusing on understanding how to engineer a new eye for those who have a retinal disease, which would enable 10 million people to regain a sense of sight.  The idea for sending an electrical current to the nerve ganglia behind the retina started in 1988 when a blind person demonstrated that he could see points of light by the ARCC (artificial retina component chip).   This method, which is still being tested, proved that the nerves behind the retina could still possibly function even though the retina degenerated.  Scientists believe that if they could replace the retina with a device that could translate images to electrical impulses then vision could be restored.  Currently researchers are concerned about electronics in the salty conditions of the eye, however.  These conditions encourage corrosion in the sometimes delicate electronics required for this technology.  Researchers, however, have designed a chip that could possibly work because it would use an external laser to power the chip.  This should eliminate the problem of the how to keep a battery working in the wet, salty environment of the eye.  The power source would have to be able to pass through the cornea without damaging the corneal tissue, though.

What Do We Have to Figure Out?
Although the artificial eye is currently being tested, there are still many issues that need to be addressed.  The biocompatibility of the implant and the human host is still in question because of the unknown effects of long-term electrical stimulation.  This stimulation could affect the retinal and cortical tissue because of the intensity needed to stimulate the nerve endings in order for a retinal response.  With the use of the ARCC it is still unclear how it affects the retinal and cortical tissue due to the electrical current.

It is also important to note that every patient has different amounts of surviving cell tissue due to degeneration caused by the ARCC use.  This is important because the electronics density required should be the minimum amount and measuring the amount of surviving cell tissue has yet to be discovered.  The attainment of high electronics densities to enhance the remaining nerves, either in the retina or cortex, seems improbable.  Safety is another major concern working with the eye.  In bionics, in general, one large unknown is dealing with the incredible complexity of the human body, and doing so without without upsetting the delicate balance of the body.
 

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