How do colour blindness correcting glasses work ?

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How do colour blindness correcting glasses work ?

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Colorblindness happens due to a lack or deficiency in one or more color-sensing cone cells in your retina. [This graph](https://upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Cones_SMJ2_E.svg/1200px-Cones_SMJ2_E.svg.png) shows the sensitivity of each of the three kinds of cones in your eyes. To identify one frequency, your brain combines the data from the cells to see how much of each was activated. So, orange light – with a wavelength of, say, 600nm – would activate *some* green cells and a lot of red cells. Much deeper red light of 650nm would activate few, if any, green cells, and a lot of red cells.

Consider, then, the color *brown* which is actually [dull orange light with bright colors around it](https://www.youtube.com/watch?v=wh4aWZRtTwU). Since it’s orange, it will activate some red cells and some green cells. Since there’s less of it than what we perceive as *orange*, it will activate fewer of both red and green cells, but the ratio between them will stay the same.

Now, consider someone with fewer than normal red cone cells in their eyes. They still have *some*, they can still actually see red light, but with fewer red cone cells it’s much harder to differentiate between slightly different shades of red. For this person, red light *always* activates fewer red cells than normal because there are fewer red cells to be activated. If they look at something that is green, it activates a lot of green a very little red – which is what people with normal vision also see. Consider if that person looks at something that is brown, though. Brown *normally* activates fewer red cells *and* fewer green cells. But this person can’t see the difference between there being no red because it isn’t there and no red because they just can’t see it well. With brown, there is also very little green, either. So is it brown, or just dark green? This person can’t see the difference.

They can see green just fine. If you put something red against something white, they can probably tell you that it’s red. They can probably do the same for something that is dark green. But as soon as you put something dark green next to something red or brown, they can’t see the difference.

Colorblindness correcting glasses are custom-ish made (or at least, the better, more expensive kind are) for the individual to correct the *ratios* between the cones that are activated. There’s no way to *increase* the red cone activation, but you *can* decrease the green so that while everything is darker and fewer overall cones are activated, they are at least activated in the same *relative* amount as they would be for someone with normal vision. For our example person with red-brown colorblindness, they would be able to distinguish the browns from the dark greens and dark reds.

However, this only works for people with a *deficiency* in one type of cone cell. They can’t help someone who lacks that cell entirely. Again, they can’t *increase* the activation, just bring everything down to match. If one of them is zero, or even just very low, you can’t match it. I’m also not sure how well it works with someone that has a deficiency in more than one type of cell. I’m sure it *could* work but I imagine there would be diminishing returns.

They don’t, at least not as advertised.

The dominant color blind glasses manufacturer started out marketing them as “gamer glasses” which had no benefit for colorblind people. The premise of the glasses was that they filter out certain wavelengths of light and that this would help people who were staring at a computer monitor for long periods of time to reduce eyestrain. They didn’t sell very many of the glasses.

They then rebranded the glasses as being for office workers, with the same line about reducing eyestrain. Again, they didn’t sell very many glasses.

Then they had a marketing campaign in which they paid “colorblind” people to try the glasses and break down crying due to being able to see color for the first time in their lives. These people were paid actors. The glasses do not let totally colorblind people see color. But this advertising campaign was a huge success and they’ve stuck with it. Fundamentally nothing about the glasses has changed since they were gamer glasses, just the marketing surrounding them.

The supposed idea as to how they work for colorblindness is that they filter out certain in between colors. Say you’re red-green colorblind. You can still see red and see green, but its hard to tell them apart when you’re looking at a mix of colors that fall between the two. These glasses filter out all of the colors between red and green. In theory this might help you to be able to differentiate between red and green by removing all of the color in between them. They also do the same thing for the blue-green part of the spectrum.

The glasses *may* help a red-green or blue-green colorblind person to differentiate between these colors. The glasses are not doing so by allowing you to see more colors, they are doing so by blocking a substantial amount of color, leaving only primary colors. The impact that these glasses would have on your life as a red-green or blue-green colorblind person are very minor, if they would have an effect at all.

Their biggest impact is actually going to be on computer monitor eyestrain – they are legitimately effective in helping to prevent that (and it is still one of the selling points if you go to their website).

The videos that you see of people crying or freaking out or whatever are paid advertisements. None of the reactions that you see in those videos are real.