Story highlights This is the first documented time these controversial cells have helped someone

During the study, stem cells derived from an embryo were injected into retinal tissue

Researcher emphasizes that the results are preliminary

Two women with untreatable eye diseases said they had dramatic improvements in their vision after injections of human embryonic stem cells, making it the first documented time these controversial cells have helped someone.

"This is a big step forward for regenerative medicine, said Dr. Steven Schwartz at UCLA's Jules Stein Eye Institute. "It's nowhere near a treatment for vision loss, but it's a signal that embryonic stem-cell based strategies may work."

Schwartz added several caveats - that the study was preliminary, only in two patients, and that it's difficult to measure vision in low-vision patients. But even so he was "thrilled and excited" about the study.

Schwartz and his colleagues published their study in The Lancet. For each patient, stem cells derived from an embryo were injected into their retinal tissue. They had to take anti-rejection drugs for a short period so their eyes wouldn't reject the foreign tissue.

Before her stem cell surgery in July, Sue Freeman, 78, couldn't take a walk, go shopping or cook by herself because of macular degeneration, a disease that affects millions of Americans and for which there is no cure.

Dr. Steven Schwartz and a 51-year-old patient who says her vision has improved after stem cell treatment.

"I couldn't pour a glass of water without spilling it on the counter," she said.

Now, after surgery in one eye, she cooks, shops and walks on her own. "I can even read my own writing now," she added. "And I've noticed other things. My husband and I were walking around one of our rental properties and I noticed scuff marks on the wall. I told him we need to fix this, and he said, 'You're seeing things better, but that's making my honey-do list even longer.'"

Schwartz, chief of the retina division at Jules Stein, emphasized that the results are preliminary and it is possible the patients' vision could get worse again. Researchers will now try the procedure in 22 more patients in research centers in the United States.

The second patient in the study, a 51-year-old woman who preferred not to use her name, said she first noticed a change in her vision a few weeks after surgery when she woke up one morning and looked at an armoire across her bedroom.

"It has a lot of detailed carvings and I thought wow, I was missing those before," she said. "I thought, is this for real?"

Later, she noticed she could see the knobs on her stove, which she couldn't see before at a certain distance.

Before having the surgery, the patient couldn't read any of the letters on an eye chart with extra large letters for people with vision problems, but after the surgery, she could read five letters on the chart, according to the study. Before the surgery, she couldn't see how many fingers an examiner was holding up in front of her face, but afterward she could.

In a commentary in The Lancet, Dr. Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest School of Medicine, warned that the report was preliminary, in only two patients, and with a short-term follow-up.

"But the results are impressive, especially considering the progressive nature of both diseases," he added.

The stem cells were derived from an embryo created in a fertility clinic by a couple that chose not to use it to create a pregnancy, said Gary Rabin, chief executive officer of Advanced Cell Technology, who said the couple donated the embryo to the company.

According to Dr. Robert Lanza, chief scientific officer at Advanced Cell Technology and a co-author of the study, the embryo was destroyed after the stem cells were derived, but in the future, doctors will be able to derive stem cells from an embryo without destroying it.

Many who consider an embryo to be human life have objected to embryonic stem cell research. In his commentary, Atala said induced pluripotent stem cells, which can be made without destroying an embryo, may also be useful. These cells, which have been derived from skin, can be derived directly from a patient, making anti-rejection drugs unnecessary.