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A severe form of inherited blindness, Leber’s congenital amaurosis (LCA), can be treated with gene therapy that has a dramatic effect, early trial results have shown.
The aim was to replace the defective gene RPE65, which plays an essential role in the “retinoid cycle” by which vitamin A molecules essential for turning light signals into nerve messages are regenerated.
In the new study – led by Dr Artur Cideciyan from the Scheie Eye Institute at the University of Pennsylvania in Philadelphia – scientists detected major improvements to the retina’s light-sensitive cone and rod cells.
Cone function, which is responsible for colour and daytime vision, increased up to 50-fold. Rods, which provide night vision, became as much as 63,000 times more effective.
However, it took several hours for the patients’ treated eyes to adapt to darkness, so that rods took over from cones. It takes up to an hour for the eyes of someone with normal vision to become used to the dark. Adaptation to sudden bright light, on the other hand, was rapid.
The researchers wrote in the journal Proceedings of the National Academy of Sciences that response to the treatment was confined to parts of the retina around where the injection was delivered.
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