Stems Cell Trial to Cure Blindness Underway in London

A revolutionary stem-cell treatment could be used to halt or even reverse age-related macular degeneration, a common form of blindness. Darren Staples/Reuters

Ten patients are to undergo a revolutionary stem-cell treatment that has the potential to halt or even reverse a common form of age-related blindness, the BBC reported.

The first patient—a 60-year-old woman who wished not to be named—has already undergone the trial at Moorfields Eye Hospital in London, using unspecialized stem cells from a donated human embryo. The patient suffers from the wet form of age-related macular degeneration (AMD), which is the leading cause of blindness in the developed world.

The trial being led by the London Project to Cure Blindness, with financial backing from pharmaceutical giants Pfizer. Ten patients suffering from wet AMD will undergo the trial over the next 18 months.

According to the Royal National Institute of Blind People (RNIB), AMD is a condition which affects the macula, a tiny part of the eye that lies at the back of the eyeball. The pinhead-sized macula contains millions of cone cells, specialized photoreceptor cells which are sensitive to light and are necessary for detailed vision, including recognizing different colors.

When a person suffers from AMD, these cells become damaged and prevent the person from seeing clearly. People with AMD often have problems focusing on things directly in front of them, such as reading a book or watching TV.

Eye diagram
Age-related macular degeneration affects light-sensitive cells in the macula, which sits at the back of the retina. RNIB

There are two forms of AMD: dry and wet. Dry AMD, which is more common, takes a number of years to develop and can cause a blank patch in central vision. Wet AMD, which affects 10-15 percent of sufferers, can develop very quickly and occurs when new blood vessels grow to compensate for the loss of function in the macula. These blood vessels can scar the macula and lead to permanent loss of central vision. AMD does not lead to total blindness, as peripheral vision is generally unaffected.

Macular degeneration accounts for almost 50 percent of all visual impairment in the developed world, making it the leading cause of sight loss among developed countries, according to the World Health Organization.

In the first Moorfields Eye Hospital trial, stem cells taken from an early-stage embryo were used to derive retinal pigment epithelium cells, a layer of cells filled with blood vessels which sits around the retina and nourishes it. When a person suffers from AMD, these cells die, causing the macular cells to stop functioning properly.

Scientists hope that by replacing these cells, they can improve or even fully restore vision. "This is truly a regenerative project," Dr. Lyndon Da Cruz, the retinal surgeon who carried out the surgery, told the BBC. "If we can deliver the very layer of cells that is missing and give them their function back this would be of enormous benefit to the people with sight-threatening condition."

The BBC reported that a previous Moorfields trial in which 40 AMD patients were treated with cells taken from their own eyes, as opposed to embryonic stem cells, showed encouraging signs. Afterwards, said Da Cruz, some of these patients were able to read and drive again. However, he added, in the long run, stem cells are preferred for this type of procedure due to the complexities of transferring eye cells and the ease with which stem cells could be produced.