Last summer UCLA scientists injected two legally blind women with cells derived from embryonic stem cells. After four months, both women showed some improvement in reading.
One patient had the "dry" form of age-related macular degeneration, the most common cause of blindness. The other had a rare disorder known as Stargardt disease that causes serious vision loss. There's no cure for either eye problem.
After four months, both showed some improvement in reading progressively smaller letters on an eye chart.
These new results come from the first tests in humans for a vision problem. Experts said the work is still very preliminary but the implications are substantial.
"This study provides reason for encouragement, but plans to now get such a treatment would be premature," said a stem cell expert not involved in the research.
Both women remain legally blind despite their improvements.
Researchers said this test was meant to study whether the stem cell therapy was safe in people and not whether it would improve vision. UCLA scientists said they were pleased that there have been no signs of rejection or abnormal growth months after the procedure.
The Associated Press contributed to this story.