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Glasses That Hack Around Colorblindness
MatthewVD writes "In 2006, researcher Mark Changizi came up with a novel theory for why humans evolved with color vision: to detect social cues and emotions in others. He built glasses called 02Amps to enhance perception of blood pooling. Some hospitals have tried using the glasses to see bruising that's not visible unaided, or help nurses find veins. But it turns out now that the glasses might be able to fix some forms of colorblindness, too."
There's an app for that: http://dankaminsky.com/2010/12/15/dankam/
These glasses don't cure colorblindness at all. They allow some colorblind people to pass some color-blindness tests by making them literally blind to certain colors (by filtering them with the lenses). The article mentioned that a person shouldn't drive with one version of these glasses because they'd be unable to see a yellow traffic light.
These glasses are interesting for other reasons, but they are not a practical cure for color blindness.
I thought red/green color blindness was associated with a defective gene for a photoreceptor protein, coded on the X chromosome. The defective gene produces an abnormal protein that responds to light in the "yellow" spectrum, causing the subject's retina to encode all red and yellow light as the same color.
Given that the gene does nothing to nerve function or distribution, perhaps the neurological effect is a result of neuroplasticity, resulting from the brain getting identical signals from different neural bundles in the eye? (Eg, eye does a LOT of signal encoding before it reaches the brain, so a loss of signal fidelity in the eye will result in a difference in higher level processing in the visual cortex, to make up for it. This could explain the retention of the after-image effects.)
Has there been a multidiscipline study conducted? As is, this data would seem in contradiction of the genetics implicated, and the existence of tetrachromatic females. If the difference was mostly neurological, and not the result of an ocular anomaly, then tetrachromats should not exist.
Hereditary color "blindness" (which can run the gamut from a mild color deficiency to severe color perceptual loss) is most commonly due to defects in the photochemicals in the cone photoreceptors. The milder forms involve shifts in the wavelength that the pigment absorbs the most. The more severe forms involve the functional loss of one photopigment. These disorders are genetic in nature. However, there are also acquired cases of color blindness caused by neuronal damage that is post-receptor, such as in optic nerve disease. Less common is color blindness due to cortical damage, such as achromatopsia.
There are two different types of red-green color blidness, basically resulting from the lack of functional red or green cones. Both red and green cones are sensitive to red and green, but in different amounts. Missing one type (or having a very low count of active cones of one type) won't make you blind to that color (i.e., objects painted with that color won't appear as black), it will just make you unable to distinguish reliably between the two hues.
That's why color-blind "simulations" typically show yellow (because it's what you get by mixing red and green). In reality, most color blind people see in red-blue or green-blue (in terms of signal) - though both red and green overlap onto yellow and even onto each other at cone level. What those people call it internally (red, orange, yellow, green) is up to them; mostly they'll try to figure out (from experience) what a trichromat would see, and they'll call it that.
If you look at a cone spectral sensitivity curve, it should be pretty obvious. The brain only gets three signals, but each signal is actually reporting a wide range of frequencies, and they all overlap to some extent.
The OP is wrong, BTW. Color blindness is due to defects in the eye, causing one or more foveal cone types to be missing or inactive.
The after image effect he mentions is from a study that showed that partially color-blind people (generally termed "color weak") can sometimes distinguish the hue of after-images better than they distinguish the hue of the original image. In some cases, this means people who are just (very) color-weak can be classified as color-blind by basic Ishihara tests. That's where the visual cortex plays a role (by making some hues more "relevant" than others). It doesn't change anything about the actual eye defects.
Interesting that the site doesn't render any content at all without javascript, pretty ironic for an article about disabilities.
I will give them one thing, their content seems to be accessible to someone with a screen reader.
Not theoretical. Empirically observed.
The mechanism at work is known as "favored X". Essentially, any given cell in a woman's body will favor expression of one or the other of her X chromosomes. This includes retinal tissues. Women who are carriers of red-green colorblindness will have a nearly random distribution of cone cells that favor expression of the defective receptor protein, resulting in tetrachromatic vision. However, since the mutation is recessive, the distribution is usually not that high, meaning being female, and carrying the mutation does not garantee tetracromacy.
relavent wikipedia page, which has some citations.