The first published clinical trial of stem-cell therapy is a tremendous boon to the company leading the experiment—but it's only a small step forward for the field.

In a paper published this week in The Lancet, scientists from the David Geffen School of Medicine at the University of California, Los Angeles, and from Advanced Cell Technology, in Marlborough, Massachusetts, reported that two patients each safely received injections of embryonic stem cells into an eye.

Stem-cell research in patients suffered a major blow recently, when one leading company, Geron, pulled out of a pioneering spinal cord repair study. The new study is more limited in scope, focusing on treatment that is easier to study and less problematic.  

The new study was written three months after treating the patients, both of whom have degenerative eye diseases and limited sight. Another three months has now passed, and Robert Lanza, chief scientific officer of Advanced Cell Technology, says both are still doing well, with no apparent side effects.

Lanza says Advanced Cell Technology would not commercialize the work itself, but would look to partner with a company that would.

The intent of the study was to show that the treatment is safe, not to look at its effectiveness. But Lanza, the paper, and a related commentary also published in The Lancet all cited the women's reports of benefits from the procedure. One woman's vision improved enough to see a hand waved in front of her face; the other climbed from 20/500 to 20/320 on an eye chart.

Kevin Eggan, an associate professor of stem cell and regenerative biology at Harvard University, says he's surprised that The Lancet published such preliminary results, and that scientists are talking about the treatment's effectiveness at such an early stage of research.