Powerful stem cells injected into the eyes of 18 patients with diseases causing progressive blindness have proven safe and dramatically improved the vision of some of the patients, scientists report.

Three years of follow up show that vision improved measurably in seven of the patients, the team at Advanced Cell Technology report in the Lancet medical journal. In some cases, the improvement was dramatic.

For instance, we treated a 75-year-old horse rancher who lives in Kansas, said Dr. Robert Lanza, chief medical officer for the Massachusetts-based company. The rancher had poor vision 20/400 in one eye.

Once month after treatment his vision had improved 10 lines (20/40) and he can even ride his horses again. Other patients report similarly dramatic improvements in their lives, Lanza added. For instance, they can use their computers or read their watch. Little things like that which we all take for granted have made a huge difference in the quality of their life.

Not all the patients improved and one even got worse. But overall, Lanzas team reported, the patients vision improved by three lines on a standard vision chart.

"They can use their computers or read their watch. Little things like that which we all take for granted have made a huge difference in the quality of their life.

The researchers treated only one eye in each patient. There was no improvement in vision in the untreated eyes.

The patients had either Stargardts disease, a common type of macular degeneration, or dry macular degeneration, which is the leading cause of blindness in the developed world. There are no treatments for either condition, and patients gradually lose vision over the years until they are, often, blind.

Lanzas team used human embryonic stem cells, made using human embryos. They are powerful cells, each one capable of giving rise to all the cells and tissues in the body. The ACT team took one cell from embryos at the eight-cell stage to make batches of these cells.

They reprogrammed them to make immature retinal cells, which they injected into the eyes of the patients. The hope is that the immature cells would take up the places of the degenerated cells and restore vision.

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Vision Quest: Stem Cells Treat Blinding Disease