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A few news stories have been circulating around about glasses that "cure" some forms of color-blindness:
Do these really work? My understanding of colorblindness is that the color-seeing cones in the eye don't exist or don't work for certain colors, so I don't understand how that could possibly be fixed by glasses...
As mentioned in an excellent Ars Technica article, they do treat (but not cure) one of the most common types of color-blindness (moderate red-green color blindness), but not all types of color-blindness. The type of people that these glasses help with are people whose red and green cones overlap more than they do for the typical human. These glasses "block the thin cluster of wavelengths detected by the excessively overlapping portion of … red- and green-sensitive cones" allowing the eyes to better distinguish colors.
In short:
In addition to the Ars Technica article, there is also a survey run by Blake Porter that reports that:
A whoping[sic] 90% of EnChroma users say they would recommend the glasses to others with color blindness. This does not come as much of a surprised because 55% reported EnChroma lenses changed their life and another 36% reported they “somewhat” changed their lives. 10% reported they did not. Furthermore, when asked if they increased their quality of life, 64% said “yes”, 31% “somewhat”, and only 5% “no”.
Here is another review from MIT Technology review that sums up the problem these glasses are trying to solve succinctly:
Color-blindness is often a result of a malfunctioning cone that causes wavelengths to overlap even more, resulting in poor color discrimination.
To help make it clear how much red and green cones overlap in their perceptions, here is an image showing how our three cones respond to frequencies of light for typical color vision:
