But instead of progressively losing more retinal cells, new cells are growing in the treated eyes. And while both women still have permanent central vision loss, both seem to see a little better.
"They do have some improvement in peripheral vision around the central blind spot, which is not coming back," study co-leader Steven D. Schwartz, MD, chief of the retina division at Los Angeles' Jules Stein Eye Institute, tells WebMD.
Schwartz warns that the stem cell treatment is being developed as a way to prevent blindness in people with early-stage macular degeneration. It's not a treatment for blindness, he says.
But to test the safety of this first-ever-in-humans treatment, the study enrolled patients with very advanced disease -- and very little vision to lose in case anything went wrong.
But the two patients did not get worse, says study co-leader Robert Lanza, MD. Lanza, a pioneer of stem cell research, is chief scientific officer for Advanced Cell Technology Inc., the company that is developing the treatment.
"Before treatment, one patient could only see hand motion. She could not read any letters [on an eye chart]," Lanza tells WebMD. "By one month she could read five letters. But that does not capture the difference in her life. She could see more color. She had better contrast in the operated eye and no improvement in untreated eye. She mentioned she could start using her computer and even start reading her watch."
Lanza and Schwartz warn that this improvement could simply be a placebo effect. They're only the first two of 24 patients in the study. And it's only a phase I study designed to test safety, not effectiveness.
"The real value of this report is what we're learning about stem cell biology, about the safety of the treatment, about the lack of immune rejection, and about how these new cells engraft in the eye," Schwartz says.
And that's a big deal, says Anthony Atala, MD, director of the Institute for Regenerative Medicine at Wake Forest University.
"This is an exciting first step, albeit preliminary," Atala tells WebMD. "This is the first published report of patients treated with human embryonic stem cells with a follow-up that shows both safety and efficacy."