Retinal regeneration

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Rods, cones and nerve layers in the retina. The front (anterior) of the eye is on the left. Light (from the left) passes through several transparent nerve layers to reach the rods and cones (far right). A chemical change in the rods and cones send a signal back to the nerves. The signal goes first to the bipolar and horizontal cells (yellow layer), then to the amacrine cells and ganglion cells (purple layer), then to the optic nerve fibres. The signals are processed in these layers. First, the signals start as raw outputs of points in the rod and cone cells. Then the nerve layers identify simple shapes, such as bright points surrounded by dark points, edges, and movement. (Based on a drawing by Ramón y Cajal.)
Section through retina

Retinal regeneration deals with restoring retinal function to vertebrates so impaired.

In findings presented in the journal "Proceedings of the National Academy of Sciences" in 2012, a Nuffield Laboratory of Ophthalmology research team led by Dr Robert MacLaren from the University of Oxford restored sight to totally blind mice by injections of light-sensing cells into their eyes. The mice had suffered from a complete lack of photoreceptor cells in their retinas, and had been unable to tell light from dark. Promising results using the same treatment had been achieved with night-blind mice. Despite questions about the quality of restored vision, this treatment gives hope to people with dysfunctional vision and including degenerative eye diseases such as retinitis pigmentosa.[1]

The procedure involved injecting rod precursors which formed an 'anatomically distinct and appropriately polarized outer nuclear layer' - two weeks later a retina had formed with restored connections and sight, proving that it was possible to reconstruct the entire light-sensitive layer. Researchers at Moorfields Eye Hospital had already been using human embryonic stem cells to replace the pigmented lining of the retina in patients with Stargardt's disease. [2][3] The team is also restoring vision to blind patients with an electronic retinal implant which works on a similar principle of replacing the function of the light-sensing photoreceptor cells.[4]

In February 2013, The US Food and Drug administration approved the use of the Argus II Retinal Prosthesis System [1], making it the first FDA-approved implant to treat retinal degeneration. The device may help adults with RP who have lost the ability to perceive shapes and movement to be more mobile and to perform day-to-day activities.

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