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I have seen a video on YouTube, where color blind people are given some glasses, and can see color for the first time in their life.

Can this possibly be true? How do these glasses work?

If color blindness is caused by the absence of cones in the eye, how can any glasses help ? Besides, if the brain has never "seen" color before, how can it even interpret it?

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  • $\begingroup$ It's probably worth your time to look up the "inverted vision experiment" to help understand how much of our "seeing" represents post-processing. The flip side of this is the vast array of optical illusions to which humans are susceptible. Every one represents a failure of the post-processing or a way in which our brains lie to us about what we have actually detected. The long and the short of it is that this is at least largely a cognitive science question rather than a physics one. And maybe a touch of philosophy as well along the lines of "How do you know we see 'red' the same way?" $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Oct 7, 2016 at 17:37
  • $\begingroup$ Did you try googling "colorblind glasses"? You might find how they work. $\endgroup$
    – sammy gerbil
    Commented Oct 7, 2016 at 17:52
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    $\begingroup$ @sammy gerbil - yes, I have seen the marketing materials you are referring to. I hope it's within the rules of SE site, to ask for a scientific and peer-reviewed opinion here. $\endgroup$
    – Martin Vegter
    Commented Oct 7, 2016 at 18:02
  • $\begingroup$ On what are you asking for a "scientific and peer-reviewed opinion"? You asked "Can it be true? How do they work?" If you had seen the manufacturer's website before posting your question you would know the answers to these questions. We do expect you to do some research on the topic before asking. $\endgroup$
    – sammy gerbil
    Commented Oct 7, 2016 at 18:16
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    $\begingroup$ @sammy gerbil - what more can I say. If you feel my question is inappropriate, and you feel insulted, then feel free to vote to have it closed/removed. $\endgroup$
    – Martin Vegter
    Commented Oct 7, 2016 at 18:31

1 Answer 1

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Our eyes detect colors using cones. There are three types of cones: S, M and L, and they are responsible for identifying the colors blue, green and red, respectively. The blue cones usually operate disjointly, whereas for most people the red and green cones might have working regions that overlap. This can be seen in the figure below.

enter image description here

This overlapping means that some frequencies might be perceived as both green or red, which explains why most color blindness is restricted to green and red tonalities. Of course, blue might be also hard to separate for some people, but that is quite rare.

Since both blue and red spectra are not restricted to the overlapping regions, if you could simply block all wavelength that could be interpreted as both red and green, then the affected person would be able to distinguish those colors without a problem. That's exactly what the glasses you're talking about do.

Addendum: The part "how can people interpret colors if they've never seen them before" has no place in this question. Color blind people can see colors as everybody else, they just can't distinguish some wavelengths one from another.

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