Another step forward for tissue engineers: "scientists have created an eight-layer, early stage retina from human embryonic stem cells, the first step toward the development of transplant-ready retinas to treat eye disorders such as retinitis pigmentosa and macular degeneration that affect millions. ... The retina is the inside back layer of the eye that records the images a person sees and sends them via the optic nerve from the eye to the brain. Retinal diseases are particularly damaging to sight. More than 10 million Americans suffer from macular degeneration, the leading cause of blindness in people over 55. About 100,000 have retinitis pigmentosa, a progressive, genetic disorder that usually manifests in childhood. ... To mimic early stage retinal development, the researchers needed to build microscopic gradients for solutions in which to bathe the stem cells to initiate specific differentiation paths. ... creating transplantable retinas from stem cells could help millions of people, and we are well on the way. ... researchers are testing the early-stage retinas in animal models to learn how much they improve vision. Positive results would lead to human clinical trials."