Imagine a day without any colour. That’s right, no fancy colour coded notes, no matching clothes and certainly no rainbows after a rainy day. This is how a person with achromatopsia, more commonly called, complete colour blindness, experiences life every day. A person with this condition sees only shades of grey. *insert 50 shades of grey joke here*. Although complete colour blindness is extremely rare, there are varying degrees of colour blindness that affect many people across the world. Deuteranomaly, protanomaly, protanopia and deuteranopia are common types of red-green colour blindness, where it is harder to tell the difference between red and green. A person with protanopia wouldn’t be able to tell the difference between a green, yellow and red light at an intersection. They would see something like the image in figure 1. Tritanomaly and Tritanopia are types of blue-yellow colour blindness, where it’s hard to tell the differences between blue and green, and yellow and red. They would see something like the image in figure 2.
A person with normal vision has 3 types of cones in their eyes, and all 3 types are needed in order for the brain to process colour. When a person has 1 or more of these cones absent or malfunctioning, their brain cannot process the colours they see, and are colour blind as a result. Dr. Jay Neitz and his team at the University of Washington are researching methods to correct red-green colour blindness and are using squirrel monkeys to do so. Yes, monkeys!!! Prior to testing, the research team taught the monkeys how to identify and touch a coloured patch hidden in a photo of grey dots. The monkeys that exhibited the deficiency of the L-opsin gene, resulting in red-green colour blindness, could not see the red or green coloured dots among the grey. With help from NIH’s national eye institute (NEI), the monkeys were then given a subretinal injection of the L-opsin gene they were missing. The gene was injected into the retinal photoreceptor layer of the eye, where the genetic info integrates into the cells and the proper proteins for colour vision can be made. After treatment, the monkeys were able to distinguish the red and green colours from the grey dots. To read more about this treatment for red-green colour blindness, refer to the article on the NIH website. https://www.nih.gov/news-events/nih-research-matters/gene-therapy-corrects-monkey-color-blindness
Another form of gene therapy for complete colour blindness was developed by the Institute for Ophthalmic Research at the University Hospitals in Tübingen and the Departments of Pharmacy and Ophthalmology at LMU. They discovered that complete colour blindness is a result of a defect in the CNGA3 gene. The team gives a patient with achromatopsia (complete colour blindness) an injection of a dormant virus that contains the normal CNGA3 gene. After a few weeks, the retinal cells in the eye will have received the normal gene from the virus and will be able to produce the proper protein associated with that gene. This form of gene therapy in humans has been successful thus far. To read more about this treatment for achromatopsia, refer to the article from the medical press. https://medicalxpress.com/news/2020-05-gene-therapy-patients.html
Fun facts about color blindness:
~ If a woman has red-green colour blindness, all her sons will also be red-green colour blind
This is because the deficiency is encoded in the X-chromosome. The deficiency is a recessive trait and therefore for a woman to have the deficiency, both of her X- chromosomes would need to code for the colour-blind trait
~People who are red-green colour blind often think peanut butter is green
~Mark Zuckerberg is red-green color blind. He reportedly chose blue for the color of Facebook’s logo because it is the richest color to his eyes.
References
Living with Colour Vision Deficiency. (n.d.). Retrieved September 26, 2020, from
Staff, S. (2020, May 01). New gene therapy for complete color blindness tested in patients.
Retrieved September 26, 2020, from https://medicalxpress.com/news/2020-05-gene-
Tritanopia – Blue-Yellow Color Blindness. (n.d.). Retrieved September 26, 2020, from
Wein, H. (2015, July 02). Gene Therapy Corrects Monkey Color Blindness. Retrieved
September 26, 2020, from https://www.nih.gov/news-events/nih-research-matters/gene-
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