The first results of human embryonic stem cell therapy are in, and they look good.

Two women, 51 and 78, who were legally blind became the first patients to receive human embryonic stem cell treatment, for their condition. The treatment, also called hESC-RPE, involved scientists injecting stem cells into each patient's eye. One woman had a condition known as Stargardt's macular dystrophy and the other, age-related macular degeneration. Both conditions cause severe vision loss. The surgery appeared safe after four months and both women experienced an improvement in vision.

"Our study is designed to test the safety and tolerability of hESC-RPE in patients with advanced-stage Stargardt's macular dystrophy and dry age-related macular degeneration," the authors wrote. "So far, the cells seem to have transplanted into both patients without abnormal proliferation … or other untoward pathological reactions or safety signals. Continued follow-up and further study is needed. The ultimate therapeutic goal will be to treat patients earlier in the disease processes, potentially increasing the likelihood of photoreceptor and central visual rescue."

Eye experts say this is an important study because it could show a promising trend in vision improvement. According to the National Eye Institute, about 1.75 million Americans currently suffer from macular degeneration, and this number is expected to grow to 2.95 million in 2020.

"Stem cell biology has an enormous potential to correct genomically derived ocular diseases, both in correcting deficiencies and amending altered anatomy and physiology," said Barrett Katz, Frances DeJur Chair in ophthalmology at Montefiore Medical Center in New York. "The eye is the very best organ to expect such advances to be made within, as it is relatively easily accessible and immunologically privileged."

The research, conducted at UCLA and Advanced Cell Technology in Massachusetts and published today in the Lancet, was small in scope and population and no patients were given a placebo treatment for the sake of comparison.

For this reason, some doctors worried the report would raise hopes prematurely.

"To reach any conclusions on the safety or efficacy of two patients treated for four months without a control population for comparison is unreasonable," said Martin Friedlander, professor of ophthalmology at Scripps Health in La Jolla, Calif. "This is why anecdotal reports like this are not published."

"This falsely raises the hopes of millions of individuals suffering from these diseases," he said.

The use of human embryonic stem cells has long been seen as an ethically controversial medical technology because many ague that an embryo is the earliest form of life. Extracting stem cells from that embryo almost always damages it.

But proponents of the use of human embryonic stem cells  say this argument lacks validity and detracts from the medical benefits that could be achieved.

"It has been over a decade since the discovery of human embryonic stem cells," Dr. Robert Lanza, co-author of the study and Chief Scientific Officer at Advanced Cell Technology, said in a statement. "This is the first report of hESC-derived cells ever transplanted into patients, and the safety and engraftment data to-date looks very encouraging… Despite the progressive nature of these conditions, the vision of both patients appears to have improved after transplantation of the cells, even at the lowest dosage.

"This is particularly important, since the ultimate goal of this therapy will be to treat patients earlier in the course of the disease where more significant results might potentially be expected," Lanza said