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Doctors in Illinois have implanted the first permanent artificial silicon retinas in the eyes of three blind patients. The outcome of the pioneering bid to restore sight using microelectronics isn’t yet known, but the undertaking is an important initial step toward realizing the goal of artificially assisted vision (see “Seeing Is Believing,” TR May/June 1999).

The experiments were led by Alan Chow, a 48-year-old ophthalmologist who is president of Optobionics, the Wheaton, Ill., company that developed the hair-thin vision chips. The prototype devices are 2 millimeters across and contain some 3,500 microphotodiodes. Placed behind the retina, this collection of miniature solar cells is designed to convert natural light to electrical signals, which are then transmitted to the brain by the remaining healthy parts of the retina.

The three patients who received the implants in June-a 45-year-old woman and two men, aged 66 and 74-all suffered from the hereditary disease retinitis pigmentosa, or RP. The illness causes blindness by damaging the eyes’ light-sensitive photoreceptor cells, known as rods and cones. “These are all patients with end-stage retinitis pigmentosa,” says Chow. “Their vision is almost as bad as you can expect from RP, which is bare to almost no light perception.”

Artificial retinas aren’t expected to produce perfect vision-far from it. But blind people would benefit from simply being able to tell whether it was light or dark outside, or pick out a person’s face across a table. Although the results of the experiments are closely guarded, a press release from the University of Illinois Chicago Medical Center, site of two of the surgeries, stated that “patients may develop some degree of vision over the location of the implant within the next month.”Chow says a detailed report of the experiments’ outcomes will be published in a scientific journal, probably within the year.

Optobionics’ is not the only manmade implant designed to replace damaged photoreceptors. At least three teams in the United States and two in Germany are at work on prosthetic retinas using one of two basic concepts. A group based at Johns Hopkins University, for instance, is working on an “epiretinal” system that uses a miniature camera mounted on a pair of glasses to capture and digitize images and transmit them to a chip placed on the front of the retina. Chow says his subretinal implant is simpler, requiring no external power or information source other than natural light.

Despite the preliminary nature of the experiments, the stakes are quite high for this rapidly evolving field. Ophthalmologist Mark Humayun, who leads the John Hopkins group, is skeptical about the efficacy of Chow’s subretinal approach and is concerned that failure could reflect negatively on all retina chip designs. “If it doesn’t work, or causes some problems, [I hope] it doesn’t give the field a black eye,” Humayun says.

The three surgeries are part of a U.S. Food and Drug Administration-approved safety and feasibility study, which allows implanting the new devices in up to 10 blind volunteers. The primary purpose of the trial is to determine whether the eye will tolerate the implants and to test surgical techniques. So far, Chow reports, the patients have recovered well and are all at home. “None have any discomfort, and so far show no signs of infection or rejection. The implant is staying in position… [and] we are also acquiring quite a bit of information and data about how the implant interfaces with the retina,” Chow says.

While time lines are hard to predict, Chow does allow for some optimism, saying that if these initial tests succeed and the device functions, “we’re hoping that within four to five years there could be a product out on the market.”

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Tagged: Biomedicine

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