Enchroma: Harnessing the Power of Light

        

         If you've ever seen Little Miss Sunshine, then you’ll remember the heart-wrenching scene when Dwayne Hoover realizes to his dismay that he is color blind, and has his dream of becoming a pilot shattered. In fact, there are many jobs you can’t have if you are colorblind, such as an electrician, a firefighter or a police officer. Colorblindness is a general term that encompasses many deficiencies in a person’s ability to perceive color. There are seven different types of colorblindness, and varying degrees of each. 

Figure 1a: Percentage of the population with varying degrees of color perception.

   


          Eyes convert light into electrical impulses in the retina via two kinds of photoreceptors, rods and cones. Rods function in dim lighting, line the outer edges of the retina and are used in peripheral vision. Cones function in bright light and provide color images and sharp outline. There are over 6 million cone cells and three different types of cones named for the wavelengths of light they absorb best- red, blue and green cones.  All other colors come from a mixture of two or more of these cone cell types. Colorblindness is the abnormal function or deficiency of one or more types of cone cell. Thus, most people who are colorblind just have a reduced ability to see colors. Approximately 8% of men and 0.5% of women have some variation of colorblindness (NIH, 2015). 

 

Figure 1b: Normal absorbance of the color spectrum.

       Enchroma is a company that is trying to combat some aspects of colorblindness. Enchroma’s glasses were derived from an invention by Don McPherson- laser safety glasses for surgeons. One afternoon, McPherson was playing a game of ultimate frisbee and was wearing these surgical glasses. His friend asked to try on McPherson’s sunglasses and when his friend, who happened to be colorblind, put them on, McPherson realized the true potential of his invention (Zhou, 2015). The glasses saturated colors because they contained embedded rare earth iron that absorbed a significant amount of light, originally to keep surgeons safe and to easily differentiate between blood and tissue. McPherson teamed up with mathematician Andrew Schmeder to optimize the glasses. Schmeder designed a filter for the glasses that targets specific photopigments. Enchroma created a method called “multinotch” filtering that cuts out sharp wavelengths of light to enhance specific colors (Enchroma, 2017). The blue cones generally work independently while the red and green cones overlap to help create intermediate colors. For example, if 10 photons land on the red cones and 90 land on the green cones, the object will be perceived as more green. However, if 50 photons land on the red cone and 50 land on the green cone, then the object will be perceived as yellow. In the majority of color blind individuals their red and green cones overlap too much, distorting the perception of colors. Enchroma glasses  absorb a band of light between the exaggerated overlapping of the red and green cones, enhancing colors by making each cone more distinct. This reestablishes the normal distribution of photons on the red and green cones. Enchroma glasses are not a cure for severe colorblindness but may help with day-to-day activities, such as driving, in individuals with mild deuteranomaly. However, recent studies involving gene therapy of these cones in monkeys have proven to be successful- a cure for colorblindness may be in our future (Casagrande, 2009).

References

Casagrande, V. (2009). Faculty of 1000 evaluation for Gene therapy for red-green colour blindness in adult primates. Nature, 461, 784-787. doi:10.3410/f.1164850.626698

Enchroma. (2017). Technology. Retrieved October 25, 2017, from http://enchroma.com/technology/

NIH: National Eye Institute. (2015, February 01). Facts About Color Blindness. Retrieved October 25, 2017, from https://nei.nih.gov/health/color_blindness/facts_about

Zhou, L. (2015, March 03). A Scientist Accidentally Developed Sunglasses That Could Correct Color Blindness. Retrieved October 25, 2017, from https://www.smithsonianmag.com/innovation/scientist-accidentally-developed-sunglasses-that-could-correct-color-blindness-180954456/