Fascinating new article in Nature: 'Gene therapy for red–green colour blindness in adult primates'

From the abstract:

Classic visual deprivation experiments have led to the expectation that neural connections established during
development would not appropriately process an input that was not
present from birth. Therefore, it was believed that the treatment of
congenital vision disorders would be ineffective unless administered to
the very young. However, here we show that the addition of a third
opsin in adult red–green colour-deficient primates was sufficient to
produce trichromatic colour vision behaviour. Thus, trichromacy can
arise from a single addition of a third cone class and it does not
require an early developmental process.