On the left is a snapshot of Venice adjusted to resemble what a color-blind individual would see. On the right, the same snapshot is shown through an EnChroma lens. The lens brings out the reds and greens, making the image much more vibrant.
Researchers at EnChroma have developed glasses that are said to enhance the colors visible to color-blind individuals without compromising color accuracy. This is a boon for the color blind as there is no cure for the largely genetic disease that afflicts 1 in 12 men and 1 in 200 women worldwide. The glasses are designed for people with red-green color vision deficiency (CVD), the most common form of color blindness. It affects 80% of those with color blindness, or an estimated 300 million people.
To explain how the glasses work, a little information is needed on color vision. Each retina contains roughly 6 million cone cells, and they are divided into those that perceive red, green, and blue light. Output from all the cones undergoes a bit of neural signal pre-processing in the retina, creating three data streams that get sent to the brain’s visual cortex via the optic nerve. The first stream or channel determines brightness, which is the sum of the signals from the three types of cones (R+G+B). The second determines an image’s blue-yellowness by subtracting the red and green inputs from the blue (B-(G+R)). And the third determines the image’s green-redness by subtracting the green from the red inputs (R-G).
People with red-green CVD suffer from one of four conditions (see R-G CVD Table below). The most common, deutan and protan, involve a color shift, which is caused by an overly large overlap between wavelengths picked up by red and green cones. These overlaps create confusion For R-G CVD, blues are unaffected, while purples are because the green-redness channel cannot resolve the correct amount of red in purple. This makes purples look blue. The same problem affects contrasting red and green colors. The viewer has difficulty resolving either color and both appear brownish.
The EnChroma glasses use multi-notch filters to selectively block signals to the red and green cones. By filtering out signals to the cones at wavelengths where there is too much overlap—wavelengths in the greenish-yellow to yellow region—the summation of cone signals generates more correct values. So the glasses try to re-establish the correct balance between the red, green, and blue cones. This, in turn, triggers the dormant neural mechanisms and uses perceived differences between colors, but the glasses do not return 100% of a person’s color vision.
What the lenses are made of and how they are made is proprietary.