Eyes are complex organs, with damage to any one part rendering a person blind. Curing cataracts may have become commonplace, but other causes of blindness remain more elusive. Now, stem cell research has made it possible for a common cause of blindness—damage to photoreceptors—to be reversed. Photoreceptors are cells in the retina that react to light and convert it into electrical signals that can be processed by the brain. They can stop functioning or die for a variety of reasons such as Stargardt’s disease and even normal age-related degeneration. Scientists at Moorfields Eye Hospital, London, and University College London have shown that these photoreceptors can be replaced, a huge leap towards curing blindness. The scientists injected thousands of stem cells primed to transform into photoreceptors into the eyes of blind mice. What they found was that these cells could latch on to the existing cells in the retina and begin to function. There are several reasons for this process to work even when the scientists begin human trials—something they say should happen within five years. The first is that working with the eye is relatively easy as the photoreceptors have to only pass on their message to one more cell for the message to reach the brain. The other reason is that immunity in the eye is relatively low, and so the new cells are less likely to be rejected.
However, the scientists still have to refine their technique—of the 200,000 cells they implanted, only 1,000 actually worked. Still, the scientists are confident they will be ready by the time human trials start—ready to bring eyesight to the blind.