By Jessica Li While many have wondered whether the colors they see are the exact same as their peers, they can agree on common colors; generally, the sky is blue, and freshly-grown grass is green. However, some have a deficiency in their ability to see color where they either mix up two or more colors or simply do not see color at all. ColorWhen individuals see color, the wavelength of light that is absorbed by said object is actually what is seen. For example, a tomato reflects back all wavelengths of light except those in the red spectrum, which leads to the tomato appearing red. The Retina and PhotoreceptorsIn the retina, there are two classic types of photoreceptors, or cells that convert light into signals: rods and cones. Rod cells are responsible for functioning in low levels of light, otherwise known as scotopic conditions, while cone cells function in bright light, contributing to photopic vision. While they do not perceive changes in light levels as well as rod cells, cone cells allow for the perception of color. Additionally, there are three types of cone cells: red, green, and blue. Color Blindness Types and Inheritance There are several types of color blindness. While most people possess trichromacy, the condition where all three types of cone cells are performing normally, those that are color blind have an error in one or more of their cone cells. Most common is red-green color blindness (e.g. protanopia, deuteranomaly, protanomaly, and deuteranopia, with deuteranopia being the most common), which causes difficulty in telling the difference between hues of red, orange, green, and blue. It is inheritable through generations via a sex-linked gene, which is why more males are affected by red-green color blindness than females—while females may have the recessive gene “covered up” by a dominant copy on her other X chromosome, males only have a single X chromosome, so whichever allele they inherit on their X chromosome is the one expressed. In the case of red-green colorblindness, the green cone cells are affected. Other less common forms of color blindness are autosomal traits, and are therefore equally likely to pop up in a person no matter the gender; those with tritanopia and tritanomaly often have difficulty distinguishing short-wavelength colors such as blue-green and yellow-red. Interestingly, while tritanopia is an autosomal recessive disorder, tritanomaly is inherited via an autosomal dominant pattern. Unlike other forms of color blindness, individuals with monochromacy are simply unable to see color. Cone monochromacy, in which an individual only has a single type of cone, prevents color from being “seen” due to the lack of a comparison baseline against other colors. Rod monochromacy, also called achromatopsia, is the most severe type of color blindness, characterized by the complete lack of cone cells. This causes the individual to only be able to see in grayscale. Both types of monochromacy are autosomal recessive disorders, and affected individuals are often sensitive to light (photophobic) and suffer from a variety of other symptoms, such as uncontrollable eye movement and reduced vision capabilities. FixesCurrently, there are no complete cures to color blindness. Despite this, there are several lenses and filters that can be used to help those that are color blind to distinguish similar colors from one another. A popular lens that attempts to “fix” color blindness is EnChroma, which does not restore color vision but enhances color. By using a special type of filtering that removes the overlap between colors, different colors are easier to distinguish between. After wearing the color-correcting glasses, users were able to identify colors they were previously unaware of. However, such technology remains in development and does not guarantee the full correction of color for all types of color blindness. Other potential treatments that are being looked into include gene therapy and treatments using growth factors. CitationsCauses of Colour Blindness. (n.d.). Retrieved November 12, 2017, from http://www.colourblindawareness.org/colour-blindness/causes-of-colour-blindness/ ColorVisionTesting | Colorblind. (n.d.). Retrieved November 13, 2017, from http://colorvisiontesting.com/what%20colorblind%20people%20see.htm Colour Blindness. (n.d.). Retrieved November 13, 2017, from http://www.colourblindawareness.org/colour-blindness/ Cross, R. (n.d.). This is how EnChroma’s color-blindness glasses achieve their powerful effects. Retrieved November 12, 2017, from https://www.technologyreview.com/s/601782/how-enchromas-glasses-correct-color-blindness/ Facts About Color Blindness | National Eye Institute. (n.d.). Retrieved November 12, 2017, from https://nei.nih.gov/health/color_blindness/facts_about Porter |, B. (2015, November 26). Color Vision and the Efficacy of EnChroma Glasses. Retrieved November 13, 2017, from http://www.blakeporterneuro.com/color-vision-efficacy-enchroma-glasses/ Ramachandran, V. S., & Brang, D. (2008). Synesthesia. Scholarpedia, 3(6), 3981. https://doi.org/10.4249/scholarpedia.3981 Rods & Cones. (n.d.). Retrieved November 15, 2017, from https://www.cis.rit.edu/people/faculty/montag/vandplite/pages/chap_9/ch9p1.html Technology. (n.d.). Retrieved November 12, 2017, from http://enchroma.com/technology/ Types of Colour Blindness. (n.d.). Retrieved November 12, 2017, from http://www.colourblindawareness.org/colour-blindness/types-of-colour-blindness/ Suggested ReadingsThe Perception of Color:
https://www.ncbi.nlm.nih.gov/pubmed/21413396 What Colorblind People See: http://colorvisiontesting.com/what%20colorblind%20people%20see.htm Synesthesia and Color Blindness: http://www.scholarpedia.org/article/Synesthesia#A_color_blind_synesthete.3B_.22Martian_colors.22 EnChroma: http://enchroma.com/
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