There are between 10 and 15 million blind and visually impaired people in the United States. Of those, around 1.3 million Americans are legally blind. "Legally blind" doesn't mean that a person is totally blind. It is possible to be legally blind and still have some vision. The World Health Organization defines 'profound blindness' as the inability to distinguish fingers at a distance of three meters (about 10 feet) or less. So some blind people may, with the aid of corrective glasses, be able to see an object 10 feet away but only with great difficulty. Only about 10 percent of the blind cannot see anything — not even light.

New technology offers hope to the millions of blind and visually impaired Americans. Researchers are busy developing and testing new treatments and devices to bring full or partial sight to the blind. This article discusses some common causes of blindness and gives examples of promising new technology that could help reverse their effects.

• Retinitis Pigmentosa (RP)
• Macular Degeneration (MD)

Retinitis pigmentosa (RP) is the name given a group of inherited diseases affecting the retina. In RP, the rod and cone cells in the retina degenerate. The rod cells are usually the first to be affected, causing night blindness. As the disease progresses, a person with RP loses peripheral vision, leading to what is commonly called "tunnel vision." The symptoms of RP may occur at any age, but most commonly appear in young adults. It is estimated that over 100,000 Americans have RP. If someone in your family has been diagnosed with RP, your family should seek genetic counseling to determine if other family members may be at risk of developing RP or if you or other family members might pass RP on in the future.

In macular degeneration (MD), the center portion of the retina, which is called the macula, starts to thin, change color or transparency, grow excessive blood vessels, or form scar tissue. This leads to a loss of central vision; things become blurry and the eye has trouble distinguishing details, both up close and at a distance. Age-related MD usually begins to develop when a person is over 50 and is most common when a person is in his or her 60s or 70s. Age-related MD is the most common cause of vision loss for Americans over the age of 55. Genetic links to MD are less clear than with RP; however, age-related MD does appear to be more common in some families than others, suggesting that there is some sort of genetic link. Less common, early-onset MD is almost certainly largely genetic and can develop in much younger individuals.

The Future Is In Sight
A number of new techniques are under development to help the blind regain at least partial vision. These treatments are still in the experimental stages for the most part, and it may be many years before they are used routinely.

Each technique treats a specific kind of blindness. There are types of blindness for which help may be longer in coming, if at all. For example, some of the treatments discussed below will only help individuals who once had sight, not those who are blind from birth.

The "eye chip": Its proper name is the "subretinal micro-photodiode-based silicon chip," but its creators prefer to call it the "artificial silicon retina" or ASR. The circular device is only 2 millimeters in diameter, 25 microns thick, and contains about 5,000 microscopic solar cells. When the device is implanted in the eye, between layers of the retina, each of the tiny solar cells is able to take light energy coming into the eye and convert it into electrical impulses, which it delivers to the damaged, partially functioning, overlying rods and cones. In the RP patients who have had the ASR transplant as part of an FDA-approved safety and feasibility study, it appears that the electrical stimulation does in fact lead to some improvement in vision. All patients noted an improvement in vision within a few weeks to a few months following surgery. For one man, his vision improved enough see his wife's face for the first time in many years.

A different kind of "eye "chip" is still years away from testing. Researchers at the Office of Naval Research in Arlington, Virginia are looking into using a cellular nonlinear network chip to create an actual artificial retina. The advantage of this kind of chip is that the computer circuits it contains are very fast and process data simultaneously, similar to how the rods and cones in the retina must process data they receive. The disadvantage of these chips is that they are currently too large and require too much power to actually be implanted inside an eye. And once those problems are solved, scientists still face the daunting task of figuring out how to connect the silicon chip to human nerve cells.

• Read more about the ASR chip in this USA Today article, "Tiny chip might restore vision in blind patients" and at the Optobionics site. For more info on the cellular nonlinear network chip, see ABCNews.com's "Eyeing a Chip That Brings Vision."

Digital camera for artificial vision: Another high-tech procedure is being developed to help those persons who are totally blind. In a system developed by The Dobelle Institute, the blind person wears a small digital video camera, mounted on a pair of glasses. Images captured by the camera are sent to a small computer worn around the patient's waist. The computer processes the images and sends the information to electrodes planted directly in the patient's visual cortex — the area of the brain that normally interprets information received from the eyes via the optic nerves. In effect, this device by-passes the eyes and optic nerves completely. The patient doesn't see what you see. Instead, he sees a black and white image that shows basic shapes of things with enhanced edges. As of the beginning of this summer, eight patients had been implanted with the first commercially-available artificial vision systems from The Dobelle Institute. In a June press conference, one patient who had completely lost his sight 18 years ago was able to use the "bionic eye" and drive a car around a test track!

• Read more about the technique in CNN's "Could bionic eye end blindness?" and at The Dobelle Institute's site, Artificial Vision System for the Blind

Gene therapy: Some of the genes that cause different retinal degenerative diseases have been identified, leading to the hope that gene therapy will become available for treating these diseases. Gene therapy is a type of treatment in which doctors introduce "good" genes into the body, and direct them to replace the "diseased" genes. Retinal degenerative diseases are candidates for gene therapy since many of the genes that cause retinal degenerative diseases have been identified, there are applicable animal models in which gene therapy can be tested, and the results of such therapy can easily be tested for with a visual examination.

• Read more about this technique: Nature Genetics Magazine Covers Gene Therapy.

• macular translocation surgery — as a treatment for age-related macular degeneration (AMD), surgeons partially detach the retina, then relocate the macula away from the area of abnormal blood vessel growth
• laser photocoagulation — also for AMD, this procedure uses laser light rays directed into the eye to destroy the blood vessels growing beneath the retina
• retinal cell transplantation — transplantation of photoreceptor cells, which has been successful in animal tests
• You can read more about these surgeries in the article, "Experimental Surgery for the Wet form of Age-Related Macular Degeneration"

All of the above represents an amazing amount of progress in a relatively short time. From understanding the genetic underpinnings of progressive eye disease to the advances in computer chips that make miniaturization of implants possible, progress made in the last 20 years has been both impressive and promising. Research and testing continues. For the blind and visually impaired, breakthroughs cannot come soon enough. But, while the future isn't here, perhaps it is finally in sight.