Colblindor joined with a recent article about Chromosomes Involved in Color Blindness. Defnitiely worth reading in the same context is the Genetics Interview with Dr. David Moskowitz of Genomed by Hsien Hsien Lei of Genetics and Health.
Divya from India asks me the following question. She tells a short story about acquiring color blindness after a heavy head injury. Here are the lines Divya sent to me:
my boyfriend suffered an injury while playin cricket recently and the optician diagnosed it as tritanopia..heres what happened..he was aplying and was kinda nauseous and he puked in his helmet and fainted and fell backwards and got a hard blow on his head from the bat and a whack from the ground at the back of his head again and got knocked out/fainted..he was out for almost an hour and when he regained consciousness he was colourblind…the optician said its tritanopia..and he can only see luminous stuff as in highlighters and violet stuff and other stuff appears gray…what i want to know is…is this permanent or is it temporary…and if it is curable how can it be done…
I will try my best to answer the above questions and give some more insights about acquired color blindness. As I am not a professional in the field of color vision professional help should be frequented for detailed clarifications.
Unfortunately color blindness can be caused by severe head injuries. By far the most occurences of color blindness are congenital. In very rare cases people with perfect color vision abilities can be affected by an impaired vision or color vision deficiency after a brain trauma, a stroke or some other kind of severe head injury.
Such vision deficiencies are caused by a damage of the optical cortex. Several cases are described in scientific papers but there are no results concerning the cause of the loss of color vision. Some speculate, that the patient’s abnormality arises from partial destruction of the chromatic mechanism. The case described by Divya above about an acquired tritanopia may also occur, if the rod-cone mechanism is damaged.
Unfortunately as much acquired color blindness as congenital color blindness are not curable or at least there are no methods known to this day. As an acquired color blindness is without much doubt caused by some damage in the optical cortex most likely there will be no cure in sight in the near future.
Also because most often a severe damage causes the color blindness, there is evidence to suggest that this trait will be permanent and not only a temporarly impairment.
Traumatically acquired color vision defect
Tritanopia – Blue-Yellow Color Blindness
Darren Rowse from ProBlogger started a new group writing project about blog goals. As I missed the last project on the topic habits of highly effective bloggers (I think I wasn’t really in the target group anyway as I am quite new to blogging) I’m joining in this time.
As this is the 101st article at Colblindor this is another good reason to think about my blog goals and share my thoughts, why I’m doing this, why I’m trying to write good content and why color blindness is worth blogging about.
Here is my list of blog goals, rated in order of appearance:
- Get to know the colors of blogging. Five month ago I didn’t know anything about weblogs and blogging. From the first moment on I was very fascinated about how weblogs are defining the new internet area and a new type of information flow. This made me feel that I had to learn more about it and this can be done best when joining the blog community with my own project.
- Write about a colorful niche. Everybody can write about almost everything. I didn’t want to have another live journal and that’s why I’ve chosen this small niche I’m writing about now. Also I couldn’t find a website which highlights all the different topics around color blindness and I think I can produce some extra value here.
- Sprinkle colors in my English writing skills. As English is not my mother tongue this is a great place to improve my English skills. Not only because of that I have chosen to write this blog in English but also because of the English reading audience is much bigger than the German. This was also in the back of my mind when choosing the language because striving for a big readership is another reason for this blog I can’t deny.
Apart from the above blog goals I also have to admit that I am a techie. That’s why I can’t sit still for a week not to try out something new in my blog. And I am also addicted to statistics. Maybe because of my studies in mathematics I can’t take my eyes away from daily hits, visits, inbound links and much more.
And last but not least I would like to earn a lot of money from blogging. But this is something I don’t emphasize as my blog goal but something that’s most welcome as soon as it starts flowing.
Two days ago it happend again. It wasn’t the first time and it definitely won’t be the last this happened to me.
I like bananas. Not as much as my son does like or better love them, but I like them. If they are not too ripe with brown dots all over, that’s how I like them most. But of course they shouldn’t be green anymore. Yellow is the color, the color of a tasty bananas.
If you read the above sentences I suppose you can already spot the problem which arises when you are affected by color blindness and would like to eat a tasty banana.
Already when I am shopping I don’t see the difference between green and yellow ones. They all look ok to me. And at home the same problem arises again: When are they ripening from green to yellow?
And that’s why from time to time I start eating a green banana. Only one bite and even I recognize the mistake. You just can’t eat a green banana, they taste horrid.
Sometimes that really bothers me. They just look the same. I can’t see any difference at all. Everybody else has no problem to see the banana isn’t ripe yet. But through my colorblind eyes they aren’t distinguishable. And that’s why I have to swallow the bitter pill or better said the bitter bite of green banana sometimes.
blue: for links (the A tag)
red: for tables (TABLE, TR and TD tags)
green: for the DIV tag
violet: for images (the IMG tag)
yellow: for forms (FORM, INPUT, TEXTAREA, SELECT and OPTION tags)
orange: for linebreaks and blockquotes (BR, P, and BLOCKQ. tags)
black: the HTML tag, the root node
gray: all other tags
As the dots are quite small my color blindness gets in my way to read the graph at its full value. It is not easy at all to tell the different dots apart from each other because the colors are not distinguishable.
- Where is the Black dot among all those Blue ones?
- Blue is very close to Violet,
- Orange flows into Green,
- Green is anyway the same as Red and
- Yellow is sometimes hard to see at all.
It would be much better to use some kind of patterns to distinguish the different types. Only three different colors should be used in graphs that they can been told apart even by colorblinds. If you have a look at the legend above you would have to choose three well distinguishable colors and two extra patterns to make the website graph more readable.
Human beings have 23 pairs of chromosomes. Out of these 23 pairs 22 are autosomal chromosomes which are equal in both sexes and encode body functions. Only one pair consists of two sex-chromosomes which are different for men and women. The 22 pairs of equal chromosomes are numbered from 1 through to 22. The sex-chromosomes are labeled with X and Y, whereas women carry the combination XX and men the combination XY. This all sums up in a total of 46 chromosomes which make the human genome.
Color blindness was actually the trigger to start mapping the human genome. It all began in 1911, when red-green color blindness was assigned to the X chromosome. This was based upon the observation that color blindness is passed from mothers to their sons. Thereby the women are usually not affected because of the normal copy, the second X chromosome. Men in contrary can not oversteer the defective chromosome, because they are carrying just one X chromosome.
The project to decipher the whole human genome is these days much more advanced. Scientists are working eagerly to encode the whole approximately 30’000 genes in the human genome.
If we have a closer look at the chromosomes which are involved into color blindness, we should distinguish between the different types of color blindness because they are encoded at different places in the genome.
- Red-green color blindness
This term combines four different types of color blindness. Protanomaly and protanopia are caused by defective or even missing L-cones (long-wavelengths). In opposite defective or missing M-cones (medium-wavelengths) are the source of deuteranomaly or deuteranopia. The genes encoding the L- and M-cone photopigments are located side by side on the X chromosome. Because of the genes are highly homologous and adjacent to one another, recombinations between them is common and can lead to anomalous pigments.
- Blue cone monochromacy
As this type of monochromacy is caused by a complete absence of L- and M-cones, blue cone monochromacy is encoded at the same place as red-green color blindness on the X chromosome.
- Blue-yellow color blindness
Tritanomaly and tritanopia which are commonly referred to as blue-yellow color blindness are caused by defective or missing S-cones (short-wavelength). These photopigments are encoded in genes which reside on chromosome 7, an autosomal chromosome. This is why blue-yellow color blindness occures at the same rate on both sexes.
- Rod monochromacy
The total loss of color vision is called rod monochromacy or complete achromatopsia. In this case the retina does not have any cone cells at all. It is known to be an autosomal recessive disease and can be provoked by different circumstances. Recent studies show that it can be encoded on chromosome 2 as well as on chromosome 8. Earlier studies assigned chromosome 14 to rod monochromacy but this could not be reconstructed.
The genes encoding L-, M- and S-cone photopigments are very well understood and determined whereas the source of rod monochromacy is a topic which still needs further research. Supposably different circumstances can cause rod monochromacy.
|Blue Cone Monochromacy||X Chromosome|
|Rod Monochromacy||Chromosome 2/8|
The table on the left hand side shows on a glance the different types of color blindness and their related chromosomes. We have at least 4 different chromosomes out of the 23 pairs which can be the source of color vision deficiencies. Further studies of the human genome will show which chromosomes carry the encoding genes for rod monochromacy as this is still a subject under research and therefore this table will maybe undergo some adjustements in the near future.
Genetics Home Reference: Chromosomes
National Center for Biotechnology Information Map Viewer
Homozygosity mapping of achromatopsia to chromosome 2
A locus for autosomal achromatopsia on human chromosome 8
If you did like this article subscribe to the feed or newsletter of Colblindor.
I put up a new poll. Actually it is the first poll on Colblindor. If possible I would like to find out if the readers of Colblindor are colorblind themselves or not. Or if they maybe don’t know yet and landed here to find out about it.
The question is as simple as this: Are you Colorblind?
Please join the poll, if you like. I will summarize the results in ten days.
As I am a mostly green guy (we have no car, I love trains and I sometimes even ride my bike to work :-) I love to share this link to a new summer service of Google:
Maybe you like it and spot some good tips for your upcoming summer holidays. As I am living in Switzerland I have to wait until they include some cities from over here.
Web designers often have a very good feeling for colors and don’t need a tool which supports choosing good color combinations. Color Schemes Generator 2 goes one step further and not only generates nice color schemes but also offers the possibilty to view the generated schemes as colorblind people may see them.
The color schemes are generated from a base color, which has to be set on the color wheel, and a chosen scheme. Five different schemes are offered to choose from:
- Mono, based on one color tint,
- Contrast, adding the complement,
- Triad, with two additional colors,
- Tetrad, based on four colors and
- Analogic, with two adjacent colors.
The angle/distance for the Triad, Tetrad and Analogic color schemes can be individually adjusted with the help of a small slider.
On a first glance the tool looks simple and easy but this main functionality is only the tip of the iceberg. You can use RGB values, circle through different saturations, adjust each color individually, reduce a scheme to web colors, choose between six different variations and even save a direct link to the generated scheme.
To me the feature of Color Schemes Generator 2 which sticks out most is the possibility of viewing a color scheme as a colorblind sees it. You can select one out of nine different types to adjust the view on the scheme: Normal Vision, Protanopy, Deuteranopy, Tritanopy, Protanomly, Deuteranomaly, Tritanomaly, Full Colorblindness and Atypical Achromatism.
If you are colorblind this is not so much of help.
For all others it gives some impressions about how colors are experienced by colorblind people. This helps a lot in choosing good color schemes and by good I mean schemes which can be seen and distinguished by colorblind people as well. One step forward towards better web accessibility.
But apart from all the good there is also a downside:
All the different possibilities of adjustments make it almost impossible to find a good color combination. If you are colorblind you have to rely on tools and you can not rely on your eyes. Too many buttons and sliders are distracting and don’t support the goal to generate a great color scheme automatically.
Direct link to Color Schemes Generator 2.
You can read some thoughts from Tom Coates at On the perception of the colours of Mars… He put a nice littel theory into the room and received quite some comments and a nice discussion around the topic.
The core of his theory goes like this:
…if we had evolved on Pluto, Jupiter or Venus, we’d perceive different wavelengths in more depth and with more variety. In fact, potentially if we’d been born on Mars, it would look to our eyes like a vibrant and colourful place, while Earth could look comparatively drab.
Reading through the comments you can learn a lot about color perception in our solar system. And also the posted links reveal a lot about the topic and let you dive even deeper into it.
And what about us colorblind?
Were we just born on the wrong planet? Maybe we would be the big guys with great vision on some other planet. For each kind of different color blindness there is out there somwhere a planet waiting. And because we are not yet ready to colonize other planets we (the colorblinds) are maybe just ahead of our time.
This is another clue to me that we colorblind people are one step ahead compared to our opponents, the not colorblinds ;-)
Thanks to Helena from Bitter Poison for telling me about this article.