Gene therapy for color blindness

Gene therapy for color blindness is an experimental gene therapy of the human retina aiming to grant typical trichromatic color vision to individuals with congenital color blindness by introducing typical alleles for opsin genes. Animal testing for gene therapy began in 2007 with a 2009 breakthrough in squirrel monkeys suggesting an imminent gene therapy in humans. While progress in gene therapy for red-green color blindness has slowed since then, successful human trials are currently underway for achromatopsia, a different form of color vision deficiency. Congenital color vision deficiency affects over 200 million people worldwide, highlighting the significant demand for effective gene therapies targeting this condition.

The retina of the human eye contains photoreceptive cells called cones that allow color vision. A normal trichromat possesses three different types of cones to distinguish different colors within the visible spectrum. The three types of cones are designated L, M, and S cones, each containing an opsin sensitive to a different portion of the visible spectrum. More specifically, the L cone absorbs around 560 nm, the M cone absorbs near 530 nm, and the S cone absorbs near 420 nm.^[1] These cones transduce the absorbed light into electrical information to be relayed through other cells along the phototransduction pathway, before reaching the visual cortex in the brain.^[1]

The signals from the 3 cones are compared to each other to generate 3 opponent process channels. The channels are perceived as balances between red-green, blue-yellow and black-white.^[1]