Definition of Color Blindness

With over two decades of experience in medicine, Melissa Flagg writes patient education articles, keeping you informed about your health.

The term color blindness is a bit misleading. It doesn’t necessarily mean the person can only see in black and white, although there are instances in which this is the case.

More often than not, the term is used to refer to someone who has difficulty making out colors of a certain color family, like blues and greens or red and pinks.

Why this happens is actually quite curious. Let’s talk about the retina first, to understand how we see in color.

The Retina

The retina is like film in a camera. It takes the images we see and sends them to the brain for processing. But, the retina is really part of the brain itself. I liken it to one huge neuron with a really long axon, or tail.

The retina is actually made up of ten layers. Since we’re not in med school, we don’t need to know all ten layers, but there is a layer in particular that affects our color vision, and that is the photoreceptor layer. This is where the rods and cones are found.

The Rods and Cones

The Photoreceptive Layer

There’s a reason this layer is called the photoreceptive layer; it’s where the image is actually captured. This layer is comprised of cells known as photoreceptors, also known as the rods and cones.

The rods are the cells that give us our peripheral vision, and they actually look like little rods. They don’t see in color, just black and white.

They are densely packed in the periphery of the retina and are completely absent from the macula. These cells are also responsible for our ability to see at night, which is termed “scotopic vision.”

The macula allows us to see fine detail and to do things like read up close. The macula is densely packed with cones.

These cells are highly specialized, and they actually look like cones. Each cone is associated with what is called a photopigment, or pigment of a certain color. There are three types of cones: red, blue and green. Cones are responsible for our daytime or “photopic vision.”

Wavelength of the Different Colors

Facts About Color Blindness

Colors are created by wavelengths of light. For example, the wavelength of the color red is about 450 nanometers. Color variations are caused by a variation in wavelength and intensity of light. If a person is lacking cones that react to the color red, that person cannot distinguish the various shades of the red color family. The same applies to blue and green.

Different Types of Color Blindness

The rainbow seen by someone with normal color vision.

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There are three different types of color blindness caused:

• Protanopia (someone who sees the spectrum in blues and yellows, and easily confuses red and green; these people also have difficulty distinguishing red light)
• Deuteranopia (someone who cannot clearly see purplish red and green)
• Tritanopia (someone who cannot distinguish blue and green or yellow and violet)

These three types are caused by a loss of one or more of the photopigments. These same deficiencies can be caused by mutated cone cells. The mutations are called protanomaly, deuteranomaly, and tritanomaly respectively.

What Causes Color Blindness?

Very rarely a person may suffer from a mutation of the cone cells, which will also result in a deficiency in color vision.

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Those who are color blind are typically lacking one or more of the photopigments. There are several different photopigments.

• Rhodopsin - found in the rods only
• Photopsins - found in the cones (there are three sub pigments in this group including red, green and blue pigments)
• Melanopsin - responsible for the circadian rhythm and pupilary light reflex. Interestingly, melanopsin has been linked to the photophobia (light sensitivity) caused by migraines.

Someone who is only missing one pigment is said to have dichromatic vision. Someone who is missing two (or all) of the pigments is said to have monochromatic vision.

Someone missing all three pigments relies on the rod cells for their vision, and because the macula is comprised of only cone cells, someone who is completely color blind also has severely reduced visual acuity.

They will never have perfectly clear 20/20 vision. Complete color blindness is very rare and is almost always accompanied by nystagmus (a condition that causes the eyes to move rapidly from side to side or up and down and do so constantly).

Color blindness is hereditary, and males are most commonly affected by it. Interestingly, the gene for color blindness is passed on by the female who is usually not affected. About eight to ten percent of men are color blind, whereas about 0.4 percent of females are affected by the disorder.

Ishihara Plate Comparison

Sometimes color vision deficiency can be caused by cataracts or medications. It can also be caused by brain damage or a syndrome known as achromatopsia. This syndrome is hereditary and is usually associated with:

• Photophobia (light sensitivity)
• Amblyopia (lazy eye)
• Nystagmus (rapid, constant movement of the eyes from side to side, or up and down)
• Hemeralopia (day – blindness)

In achromatopsia, the patient is completely color blind, and this affects their ability to see clearly. In bright daylight, their vision is terrible because the cones in the macula do not work. However, in low light conditions, they see very well because the rods allow us to see at night and in low light.

Color Blind Recessive Gene

Ishihara Color Plates

This plate is the first plate in the book and is used to show the patient how the test is performed. It can be seen by patients with normal vision and those with color deficiency.

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Diagnosis of Color Deficiency

Someone who is color blind is easily diagnosed. There are several tests that can be performed by your ophthalmologist to determine quickly and painlessly if you have a color deficiency.

The most common test used for this purpose is the Ishihara Color Plates. These color plates are used to both diagnose color blindness and determine the type of color deficiency.

There are several other tests to diagnose a patient with this disorder.

The Farnsworth Munsell 100 Hue test is another diagnostic test to determine both if a person has a color deficiency and if so, which one. This test is quite lengthy, and can be difficult. There is a shorter version of it called the D-15.

Other tests are available, but are rarely used. However, in cases of color blindness caused by medication, a visual field test may be given using a red stimulus to determine if a patient has lost sensitivity to the color red.

Farnsworth Munsell 100 Hue Test

Treatment of Color Blindness

Unfortunately, there currently is no treatment for color blindness that is inherited. Sometimes color blindness can be caused by the aging process.

Cataracts, for example, can cause a change in color vision because of the yellowing of the lens. Once the cataract is removed, however, the patient’s color vision is restored.

In some cases, color vision deficiency can be caused by medications. A patient with rheumatoid arthritis, for example, may be taking Plaquenil to alleviate symptoms and halt progression of the disease.

After long term use of this drug, the patient can develop a red – green deficiency because of a side effect known as Plaquenil toxicity. The only treatment is to stop taking the medication. But, most of the time the benefit of the medication is worth the risk.

Patients have told me that they have “heard” color contacts can fix a color vision deficiency. This is completely incorrect. Color contacts are 100 percent cosmetic.

The color of the lens is limited to the iris only, and does not cover the pupil; therefore it does not affect the ability of the retina to see colors.

I have also been asked about glasses specifically designed to eliminate glare. Again, this is misinformation. Glasses that eliminate glare have a yellow tint to them.

These glasses alter color perception (which is why the military does not allow them to be used as safety glasses), but they do not fix a color deficiency in someone who cannot see color, especially someone with tritanopia (blue – yellow deficiency).

If you think you have a color deficiency, or other eye problem, see your ophthalmologist right away. If you take medications like Plaquenil or methotrexate, make sure your doctor knows, and have your color vision tested regularly.

It’s important to see your ophthalmologist on a yearly basis, even if you don’t have any eye problems, in order to catch eye diseases before they become a problem.

This content is for informational purposes only and does not substitute for formal and individualized diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed medical professional. Do not stop or alter your current course of treatment. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2012 Melissa Flagg COA OSC

Comments

Melissa Flagg COA OSC (author) from Rural Central Florida on September 30, 2012:

You're more than welcome. I have no idea how it ended up in my husband's inbox though... I feel really bad!

Zulma Burgos-Dudgeon from United Kingdom on September 30, 2012:

Yes I did get your email. Just mulling over some of the points you brought up. Thanks for your input.

Melissa Flagg COA OSC (author) from Rural Central Florida on September 29, 2012:

Ah, ok that makes much more sense! :D

Ka'imi'loa from Tucson, AZ. on September 29, 2012:

@Daughter Of Maat...the 3-D reference was from the old school Red/Blue glasses, I am able to see today's technology advanced 3-D films.

Melissa Flagg COA OSC (author) from Rural Central Florida on September 29, 2012:

@benisan thank you! I'm glad I could help you understand your condition. It's clear you have a wonderful, loving mother!

Not being able to see things in 3-d, also called stereo vision or stereopsis, is not related to color blindness. It is most commonly found in patient with a lazy eye or muscle imbalance that causes the eyes to be misaligned.

Ka'imi'loa from Tucson, AZ. on September 29, 2012:

I really enjoyed how you put into terms where someone like me could understand. I do not see my Red's or Green's, and the inside family joke is that I have always been depressed as a child during Christmas season, because I could not enjoy the colors the way everyone else got to see the lights and color patterns and designs. My mother celebrated decorating the tree and the house when I was a keiki (child), with clear bulbs, she used to remove the colors from the bulbs she had bought with finger-nail color remover.

I really don't know how much I am missing out by not being able to see the colors I am unable to view? 3-D...forget it! No third dimension in this man's life.

Melissa Flagg COA OSC (author) from Rural Central Florida on September 29, 2012:

@tlmcgaa70 Wow thank you!! I checked out the paper, and I saw quite a few articles on there I'm going to have to read! I'm honored to be on such a site! Thank you!!

Melissa Flagg COA OSC (author) from Rural Central Florida on September 29, 2012:

@phoenix, better late than never!! Did you get my email??

Good point about the bombs, although I would think that would mainly apply to someone who was completely colorblind, but I've never worked on a bomb, so I have no idea. I guess its better to be safe than sorry!! My dad was color blind and he was also an electrician! He never had a problem. Scary thought though!!

tlmcgaa70 from south dakota, usa on September 29, 2012:

DaughterofMaat, i shared your hub via twitter...and sara gunderson posted in her "paper"..check it out...http://paper.li/montanansky

Zulma Burgos-Dudgeon from United Kingdom on September 29, 2012:

Hi DOM. Sorry for the late response but I finally got here. Great hub, as per usual. I always thought colour blind meant just that; that you couldn't see colours at all.

I believe the reason many military personnel are locked out of jobs because of colour blindness is because there are jobs, such a bomb disposal, where you have be certain of your colours so as to avoid grevious errors. On the other hand, I knew a man who was colour blind and had a job in the electronics field. I guess his colour blindness wasn't an issue.

Melissa Flagg COA OSC (author) from Rural Central Florida on September 28, 2012:

@amberId, I'm glad this hub helped you test your son, that's awesome! Sometimes at that young age, it's not the cone cells, it's the connection between the retina and the brain. Those pathways sometimes take a litllte longer to mature.

:D

Melissa Flagg COA OSC (author) from Rural Central Florida on September 28, 2012:

@Lizzy You are absolutely right, there are variances in monitors, plus staring at a computer screen isn't the best way to take the test. I know how my eyes feel after writing all day!

When I tok the test (I couldn't help it while writing this hub!) I scored a 7, which is about right. I have a very slight red/green deficiency that doctors were never able to pick up. I found it testing myself! lol

Liz Elias from Oakley, CA on September 28, 2012:

I scored 12 on that test...which, just like 'tlmcgaa70' said, surprised me, as I thought I had it down pat. HOWever---there is this to be said for trying to take such a test online:

1) Not every monitor displays colors the same, and

2) the black lines separating the squares could cause some misplacement, preventing, as they do, from direct side-by-side comparison as you'd have, for example, with paint chips.

I believe if it was a physical test with actual cards, I'd have aced it. ;-)

Amber White from New Glarus, WI on September 28, 2012:

great hub! We thought our son was color blind for a time, my uncle is and my grandfather was. My son used to confuse red and green all the time as a toddler. Now he is in first grade and I just had him look at the color plates. He could tell me all the numbers in the color plates and he told me the rainbow properly in order. He has not confused colors really since 4K, now, and I feel even better after having him read the numbers. Voted up and shared!

Melissa Flagg COA OSC (author) from Rural Central Florida on September 28, 2012:

@tlmcgaa70 Unfortunately, I couldn't view the results, it just took me to the test again. But a score of 39 definitely says you have a problem seeing colors. Although, since it hasn't bothered you, you've probably adapted. I'm glad my hub could help you!! Thanks for commenting and sharing!!

Melissa Flagg COA OSC (author) from Rural Central Florida on September 28, 2012:

@DzyMsLizzy it's amazing to me how many people who are colorblind are artists!! And then I read about someone in the military being rejected for a job because he's colorblind, which happens quite frequently. It's ironic to me that artists can make it work, but a soldier can't?

It could be a recessive gene on both sides. You may carry the recessive gene and your ex may have carried it as well. It doesn't have to be a dominant gene in a male, although it usually is, there are exceptions. :D

Thanks for stopping by! I've missed you! :D

tlmcgaa70 from south dakota, usa on September 28, 2012:

Holy Dodgers! i went and took that test, where you drag and drop in order of hue. i thought it looked perfect and i for sure was gonna score close to zero...39! i am shocked to say the least. here is my results.

http://www.xrite.com/custom_page.aspx?PageID=77

i never knew i had a problem with colors. what an eye opener this hub was and this test. voted up and then some and definitely shared!

Liz Elias from Oakley, CA on September 28, 2012:

A most interesting, professional and thorough explanation of this condition.

My husband is color blind, (green/red), and he states that it is most difficult for him around dusk; he says then, everything becomes shades of gray and he loses some depth perception...so he does not like to drive at that time of day.

Interestingly, he is a very talented artist, and used to do oil painting...he figured out ways to compensate in order to make his paintings ring true.

Interestingly, my grandson, who just joined the Army, was rejected for his chosen MOS because of color-blindness, and had to pick an alternate job--but my current husband is not his grandfather, and I don't believe my ex was color blind. I've no idea where it came from. I don't know that anyone in my family had the condition, so even passed down through the female lines, some male had to have had it, I would think....

Voted up, interesting, useful and shared across platforms.

Melissa Flagg COA OSC (author) from Rural Central Florida on September 28, 2012:

@rahul Thank you! I'm sure your friend will appreciate all the info you babble at him lol

Jessee R from Gurgaon, India on September 28, 2012:

Interesting and enlightening read... i have a friend who has this condition...

Now I will babble him with the facts... :)

Melissa Flagg COA OSC (author) from Rural Central Florida on September 27, 2012:

@Pamela, wow! It is so rare for a girl to be color blind! That's really fascinating, and her painting sounds beautiful. Color is really all about perception I think. Personally, I think we all see colors a bit differently because of how the brain interprets the images. I sometimes wonder if what we see as blue is actually blue! :D

Thanks for commenting and sharing! Greatly appreciated!

Melissa Flagg COA OSC (author) from Rural Central Florida on September 27, 2012:

The color plates are fun aren't they lol. I actually always enjoyed testing patients with the color plates. We didn't do it frequently, so it was a treat when I had to do it.

When you say above 20/20, do you mean slightly worse, like 20/30? or better, like 20/15? Just curious :D

Thank you for the share and pin! I accepted your invite, that board does have awesome hubs on it! :D I'm honored to be on it! Thank you!

Pamela Dapples from Arizona now on September 27, 2012:

This was very interesting. I enjoyed it very much. I especially like your color, frequency and wavelength chart as the whole concept of it -- the amount of light shining on an object -- has always fascinated me. There is so many amazing concepts on this earth.

On a day-to-day basis, I've become familiar with 'color blindness' because my husband, both sons and daughter are color blind to some degree. The way the doctor explained it to me about our daughter is that it likely was passed on to her through my dad -- who is also color blind. None of them let it affect them. My daughter is a really good artist. But the first sunset and water scene she ever painted when she took up painting -- was green and orange. It was really pretty. I told her it was really nice even though I'd never seen a green and orange sunset before. She was amazed. She said it's that color every night.

A year or so ago (on Maui) I saw a similar painting to hers in a gallery with a price tag of over $3000. Just shows us that the world is beautiful no matter which shades we view it in.

Great hub. Voting up and useful.

Brett C from Asia on September 27, 2012:

An interesting read. I just started work in South Korea and had to undergo a full medical check up. Thankfully everything was OK. However, I did get to experience the colour plates colour blindness test and also the full eye test. I was happy to discover having slightly above 20/20 vision ... although I don't know how you would class it lol. Was interesting nonetheless.

Shared, up, interesting and pinning to 'Awesome Hubpages' for which I have sent you an invite (it is a board where the pins show on many profiles and that you can edit to invite others!).

Melissa Flagg COA OSC (author) from Rural Central Florida on September 16, 2012:

Thank you Frank! I'm so glad you were able to learn something from it! You've made my day! :D

Frank Atanacio from Shelton on September 15, 2012:

Maat, what an educational, interesting Hub.. I really never think of looking into these things and I do have a friend who is color blind.. now I understand a little more about his condition thanks and bless you :) Frank

Melissa Flagg COA OSC (author) from Rural Central Florida on September 14, 2012:

That's what I've heard from most patients. It seems the mind is quite capable of overcoming obstacles like this. My hubby has problems with dressing our daughter lol. Thankfully, his wardrobe isn't very colorful and I think that's because he's a partial tritanope. Numbering clothing items is a brilliant idea. It works well for kids too. Parents can put the numbers in the colors the child can't recognize and help them learn what that color looks like to them. It won't work for all colors, but it can make a big difference.

Paul Edmondson from Burlingame, CA on September 14, 2012:

Yep, been color blind all my life. It's only an issue when I dress myself:) Usually Robin tells me when things don't match, but when she's not around, or when I travel she sometimes puts numbers on things so I know that I can wear all the things marked 1 together. Other than that I usually default to others on color choices:)

Melissa Flagg COA OSC (author) from Rural Central Florida on September 13, 2012:

@Carol Thank you so much!

Melissa Flagg COA OSC (author) from Rural Central Florida on September 13, 2012:

@kashmir56 Thank you! My hubby understands it more now as well! :D

Melissa Flagg COA OSC (author) from Rural Central Florida on September 13, 2012:

@Mazzy, I actually learned something too while writing this. I didn't realize it was violet and yellow that tritanopes had a problem with, although when I read it, I went AHA! lol. I may write more on the subject, I found it fascinating!

Melissa Flagg COA OSC (author) from Rural Central Florida on September 13, 2012:

@leahlefler Thank you! I thought the flag was awesome too! It really allows people to fully understand what it is to be a protanope or tritanope. I've had a few young patients that had similar problems to the boy you described. We teach them how to use visual cues to distinguish color shades. Most kids do really well if they are taught early.

Melissa Flagg COA OSC (author) from Rural Central Florida on September 13, 2012:

@TT Thank you!! I did do a bit of research on this one. Since my hubby is just slightly color blind, and we're always arguing over teal versus green, it was really interesting to me. I'm glad that came through in the hub! :D

Melissa Flagg COA OSC (author) from Rural Central Florida on September 13, 2012:

@effer, thank you, love your puns! ;) Most people don't know exactly what color blind means, it is a bit of a broad term. Most of my patients thought it meant everything was black and white, and I suspect that's what most people think!

Melissa Flagg COA OSC (author) from Rural Central Florida on September 13, 2012:

THANK YOU!! I did not see that, and greatly appreciate you pointing it out.

I'm assuming you've been color blind all of your life, did you have any problems growing up? I'm always curious if patients have always known they were color blind or if was ever even an issue.

Paul Edmondson from Burlingame, CA on September 13, 2012:

I love this hub...being color blind.

I think you have this paragraph twice in the hub.

Someone missing all three pigments relies on the rod cells for their vision, and because the macula is comprised of only cone cells, someone who is completely color blind also has severely reduced visual acuity. They will never have perfectly clear 20/20 vision. Complete color blindness is very rare and is almost always accompanied by nystagmus (a condition that causes the eyes to move rapidly side to side constantly).

Suzie from Carson City on September 13, 2012:

DO....for the longest time I was in the dark (no pun intended) about just what was meant by "color blind." You have certainly made it very clear, easy to comprehend and quite interesting, I might add. You are a wealth of information in this particular field and EYE, for one, appreciate it!!

Thank you!.............UP+++

Terrye Toombs from Somewhere between Heaven and Hell without a road map. on September 13, 2012:

Very useful information, DOM. Given that you are extremely experienced in this, it still looks like you took a long time and engaged in a lot of research to bring this wonderful hub to fruition. Great job! Voted up and more.

Leah Lefler from Western New York on September 13, 2012:

This is really great, Daughter of Maat. I LOVE the rainbow flag with the examples of the different ways a person would see it if they had protanopia, tritanopia, etc. Very interesting! There was a boy in my son's kindergarten class who couldn't identify some of his colors and they wanted to refer him to special services... but then they realized he was simply color blind!

carol stanley from Arizona on September 13, 2012:

Very helpful for all of us to know. Lots of good information here. Voted Up and share.

Thomas Silvia from Massachusetts on September 13, 2012:

Thanks for this great explanation of color blindness i do understand it better now. And when brother talks about his color blindness I'll understand more clearly what he means. Well done !

Vote up and more !!! SHARING !

Mazzy Bolero from the U.K. on September 13, 2012:

I found this fascinating, Daughter of Maat, and it appears to have solved an old mystery for me. I had a boyfriend who said he was red-green colorblind. Once, when wearing a lilac dress, I asked him what color it was. I thought he would say blue, but he said, "It's yellow." I couldn't figure that one out, but now I see there is a type of colorblindness that confuses violet and yellow. We can never know how other people see things, but it's helpful to have some insight so you can at least try to imagine it. Voted up and shared.