What's happening as stem cell treatments are tested in people.
Goal: Use limbal stem cells (taken from the outer border of the patient's cornea) to improve vision for people with corneal disease, the No. 2 cause of blindness.
Does it work: A British study concluded that transplanting limbal stem cells "is a safe and effective method of reconstructing the corneal surface and restoring useful vision in patients."
Goal: Use human embryonic stem cells to make specialized cells to help treat Stargardt's macular dystrophy and dry macular degeneration.
Does it work: Testing is under way but is still in the early stages. The U.S. biotech company Advanced Cell Technology is conducting the trials.
Early success: Results have been reported for two patients, the first in each clinical trial for Stargardt's macular dystrophy and dry macular degeneration. Both patients had no side effects. Both had "measurable improvements in their vision that persisted for more than four months," the nonprofit Alliance for Regenerative Medicine states in its Annual Industry Report 2012. But larger studies are needed to check the procedure's effectiveness.
What's being done: Two different approaches are being explored. One is to use patients' own stem cells to make pancreatic cells, called beta cells, that can release insulin on demand for people with type 1 diabetes. If successful, the treatment could free patients from insulin injections.
Does it work: In an early study, the experimental procedure using patients' own stem cells, plus drugs to suppress the immune system, helped 15 teens with type 1 diabetes stay off insulin injections for about 1.5 years, on average. There were some side effects, most of which were temporary, and the study's small size means the results are preliminary. Clinical trials of the treatment using human embryonic stem cells have not begun.