Stem Cells
Age-related macular degeneration (AMD) causes about half of all causes of blindness in older people. The disease gradually damages the macula, the small but vital area at the back of the eye that supports sharp central vision.
AMD typically develops as people age and it is most common in people over 60. About 15 per cent of Australians over 80 have vision loss caused by AMD. They lose the ability to read, watch TV, drive and recognise faces.
There are two main forms of AMD. The dry form occurs 90 per cent of the time. It is caused by the slow breakdown of retinal cells that help the eye process detail and colour. The wet form is less common but progresses more quickly and is caused by abnormal blood vessel growth underneath the retina.
There’s no cure for AMD. However, eye injections can prevent further vision loss in the wet form of AMD.
There is no known treatment for dry AMD, however preliminary results from two ongoing trials in the USA offer hope not only of preventing but of reversing vision loss.
University of Michigan trials have found that stem cell transplants are safe and can significantly improve vision, even in severely affected patients.
Six trial participants with advanced dry AMD received transplants in one eye of specialised stem cells originally sourced from eye-bank tissue. These adult stem cells were limited in function and could only mature into retinal pigment epithelial cells.
To be successful, stem cells have to be tolerated by the eye, attach themselves to the retina and establish neurological contact with optic nerve cells.
The participants were given the lowest dose of the treatment (50,000 cells) during eye surgery. The procedure proved safe, with no serious inflammation or tumour growth reported in any of the patients.
In addition, participants had unexpected vision improvements in the treated eye, while their untreated eye did not change.
“We were surprised by the magnitude of vision gain in the most severely affected patients who received the adult stem cell-derived transplants,” said Rajesh Rao, Professor of Ophthalmology and Visual Sciences at the University of Michigan. “This level of vision gain has not been seen previously in a group of patients with advanced dry AMD.”
Meanwhile scientists at the University of Southern California, Roski Eye Institute, are beginning a phase 2b clinical trial to test whether stem cells can be used to replace damaged retinal cells and potentially restore vision.
The researchers grew embryonic stem cells in a laboratory and treated to develop into retinal pigment epithelial cells, the cells that make up the active part of the retina, prior to transplanting into eyes.
They attached the stem cells to an ultra-thin implant, thinner than a strand of hair, designed to hold the cells in place once inserted into the eye.
“We are hoping to determine if the stem-cell based retinal implant can not only stop the progression of dry age-related macular degeneration, but actually improve patients’ vision,” said retinal surgeon Sun Young Lee.
The trial built on earlier research conducted by Roski Eye Institute specialists involving a small group of patients. That initial study found the implant was safe, remained securely positioned in the eye and was successfully absorbed into the retinal tissue.
Unexpectedly 27 per cent of participants experienced some level of vision improvement.
Having established that the procedure is safe, further trials are planned with a larger number of patients and a bigger dose of stem cells.
“Stem cell-derived retinal implants may offer one of the greatest possibilities for helping patients with dry age-related macular degeneration and one day, may ffer a cure,” said Dr Mark Humayun, co-director of the USC Roski Eye Institute.