February 6, 2025 • 17 mins
Colour Blindness: Have you ever wondered what the world looks like through the eyes of someone with colour blindness? From vibrant reds to soothing greens, our perception of colour shapes everything around us. But what happens when that vivid spectrum fades? What if the beautiful colors of a sunset or the vibrant hues of a blooming garden were all a mystery to you? Colour blindness affects millions, reshaping their perception of the world in profound ways. But what actually causes it? What are the different types of colour blindness? And how do we actually test for the condition? Join us as we embark on an exciting journey through the captivating history of colour blindness. We’ll explore the various types and the genetics that govern this condition, revealing the surprising inheritance patterns that shape how we see (or don’t see) colour. But that’s not all—prepare to discover alternative causes of colour vision issues that may surprise you! Tune in to learn more!
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Resources:
Natasha Caudill (instagram): https://www.instagram.com/natashacaudill?igsh=dnJseW1nM3J1NG45
References:
https://bondeye.com/advancements-color-blindness/
https://www.science.org/doi/10.1126/science.7863342
https://medlineplus.gov/genetics/condition/color-vision-deficiency/
https://www.mayoclinic.org/diseases-conditions/poor-color-vision/symptoms-causes/syc-20354988
https://medlineplus.gov/genetics/condition/achromatopsia/
https://my.clevelandclinic.org/health/diseases/11604-color-blindness
https://www.colorblindguide.com/post/famous-colorblind-people-of-our-time
https://enchroma.com/blogs/beyond-color/interesting-facts-about-color-blindness
*This podcast is for entertainment purposes only. If you suspect you have a medical condition, please seek out an opinion of a medical professional.*
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
During a pick up from preschool for your little boy Oliver, his teacher pulled you aside and
(00:04):
you braced yourself, thinking he had potentially gotten himself into trouble again with his
cheekiness.
But to your surprise, her inquiry took a different turn.
Have you noticed Oliver struggling with colours at home?
She asked.
Her brow furrowed with genuine concern.
Your mind raced.
Colours?
Surely he knew red from green, right?
Confused you asked what she meant by that.
(00:24):
And she explained that during their lessons on colours, he was unable to differentiate
between some of them.
Intrigued and a bit concerned, you decided to test him at home and quickly discovered
he indeed struggled with recognising certain colours.
This has led you to the decision to schedule an eye test for him.
(00:55):
Hello and welcome to Anatomy of Illness.
Today's episode is about colour blindness.
Before we get into the condition, we are going to start with the history.
So why do we know colour blindness exists?
We begin in 1794.
This is when John Dalton would describe his and his brother's colour blindness.
Dalton was a respected physicist and chemist during his time.
He found that he often mistook red for green and pink with blue.
(01:17):
He would compare his vision with others using a book of silk threads in an attempt to understand
how others perceived the world.
John Dalton came to the conclusion that there may have been an abnormality in his eyes causing
his perception of the world to be different.
He suggested that the vitreous humour, which is the fluid in the eye, was different.
He believed that his had a blue tint, or he had some sort of pre-retinal filter.
(01:38):
Dalton in his will requested an autopsy be performed on his eyes to see if his theory
was correct.
This autopsy was performed in 1844 by Joseph Ransome, who was his medical attendant.
In this examination of his eyes, he collected the humour from one of them to examine it.
It was completely normal, there was no blue tint.
He removed the lens of one eye and examined it.
(02:00):
The lens did have some yellowing, but this was not from colour blindness, this was actually
due to the ageing of the eye.
Dalton had reached the age of 78, so his eyes were naturally deteriorating.
Ransome also cut off the posterior pole of the eye, so the very back of the eye, and
looked through it.
He noted that there was no colour distortion for scarlet or green objects when observed
through the part of the eye, like Dalton believed there would have been.
(02:23):
Ransome did not get rid of his superior's eyes, no he stored them in air.
Interestingly enough, DNA was later taken from these and tested.
Dalton's theories were incorrect on what could be causing his Daltonism.
Yes, this was what they were calling colour blindness at the time.
The other theory that was popular at the time was that there was a defect in the brain.
Interestingly enough, what was written on the autopsy of John Dalton, is that his Daltonism,
(02:47):
or colour blindness in today's terms, was caused by deficient development of the phrenological
organ of colour.
This was corresponded to part of the frontal lobe.
Phrenology is a no longer used science I have covered on our YouTube channel, which you
can check out.
This measured the bumps and dips in a person's skull, equating it to a person's traits.
The frontal lobe does not affect a person's colour vision, nor does it correspond to vision
(03:09):
at all.
You have to go to the back for that, the occipital lobe.
Now we move back to 1785, just for a little bit.
With a publication in a general German science magazine.
In this there was a theory pushed forward by a person named Giros von Gentilly.
They claimed that there were three types of membrane, or molecules, in the retina corresponding
to the three types of light.
(03:30):
Colour blindness would occur when one or two of these three kinds of molecule or membrane
were either paralysed or overactive.
This theory may have helped Thomas Young, who combined the idea of the three receptor
theory and the physical hue as a continuous variable.
He used this to explain Dalton's colour blindness.
He claimed the absence or paralysis of those fibres of the retina, which are calculated
(03:51):
to perceive red, were to blame for his colour blindness.
Moving forward to 1855, with the arrival and end of the industrial revolution.
We had many new inventions.
One of these being trains.
Now why would a medical podcast care about trains?
Well with trains we inevitably have train accidents.
In 1855 colour blindness was viewed as potentially dangerous and as a threat to life.
(04:14):
This is evident in the publication by Edinburgh Professor of Technology, George Wilson.
This publication was titled, Researches on colour blindness with a supplement on the
danger attending the present system of railway and marine coloured signals.
This would not be the only train based colour blindness crossover.
There were actually many railway accidents linked to colour vision defects leading to
(04:37):
the unease from the era to even leak into the literature.
This is highlighted in the work of Charles Dickens, more specifically his 1866 short
story The Signal Man.
This came out about a year after he was involved in a fatal train crash, the Staplehurst rail
crash.
More specifically.
In this book colour blindness is alluded to, with his anxiety towards the red light.
(04:58):
As the apparitions he sees linked to the deaths are linked to the red signal light.
It indicates the characters sense of sight was impaired.
Moving away from Dickens and to 1875 we meet physiologist Frifthiof Holmgren.
He linked a railway workers inability to distinguish between red and green signals to a fatal crash
that occurred in Sweden.
This would lead Holmgren to actually create a test for colour blindness.
(05:21):
He had test subjects match little skeins of wool.
So skeins is just like a little group of threads.
Trains were not the only form of transport affected, no.
Don't worry boats were affected too.
Not the Titanic though, that was an iceberg.
This is evident in the 1895 writings of an ophthalmologist by the name of Thomas H. Bickerton.
“It is now no uncommon thing to hear of officers being dismissed for colour blindness, who
(05:43):
have held in some cases for years lucrative and responsible appointments on board ships.”
Ship workers and railway workers could be fired for colour blindness or abnormal vision.
Or in some cases they were exploited by others who threatened to reveal their defect, if
this was found out.
This is also evident in the literature from the time.
In the 1902 short story by Joseph Conrad, who was actually a sailor prior to being an
(06:04):
author, this story is called The End of the Tether.
In this story the main character, who is an aging skipper, hides a visual defect from
the ship's owner.
He finds out and begins exploiting him.
The story does not directly mention colour blindness, however when the first mate finds
out about the main character's condition, he experiences symptoms out of sympathy.
Examples of this in the book are, “the sun had turned blue” and “the very colour of the
(06:28):
sea seemed changed.”
Moving to 1917 and sailing all the way to Japan to meet Shinobu Ishihara.
Dr Ishihara was an ophthalmologist, who invented the Ishihara tests.
If you have ever seen those colourful spotty circles with a number in them, then you have
seen an Ishihara test.
This test was initially developed for the Japanese military, as he was a doctor for
(06:49):
them, when he created it in 1916.
But in 1917 it became widespread.
These are a common test still used today to determine colour vision defects.
If you are enjoying this episode and think someone else might enjoy it or find it valuable,
make sure to share it with them.
It helps us grow and helps us keep the lights on.
So what causes colour vision?
Colour vision is caused by cone cells in the eyes.
(07:09):
These come in three types.
Red sensing cone cells, also known as L-cones.
These sense the long wavelengths of light, so around 560 nanometres.
Green sensing cone cells, also known as M-cones, they sense the middle wavelengths.
These are around 530 nanometres.
And finally the blue sensing cones, known as the S-cones.
(07:30):
They sense the short wavelengths of light, which are around 420 nanometres.
For the majority of people, these are all present and work normally.
This is colour vision or trichromacy.
Speaking of colour, did you know we have a great colour selection of merch on our website
merchanatomy.com?
Anyway, back to the eyes.
For those who do not have all of these present or they do not work correctly, they will have
(07:52):
some form of colour blindness.
What are the types of colour blindness?
The categories that directly talk about how many cones are present are (07:56):
anomalous trichromacy.
So in this form, all of the cones are still present, but one isn't as sensitive to light
as it should be.
In this type, you don't see colours in the traditional sense.
In the mild form, you may confuse pale and muted colours.
In severe cases, you may confuse more vivid colours.
These are the types that normally end in anomaly.
(08:18):
Essentially, it means partial vision of a specific colour. Dichromacy.
In this type, one kind of cone is missing.
So you have only two kinds of functional cones.
So you are only able to see the world through those wavelengths of light.
With this kind, it is often hard to tell the difference between vivid colours.
This is the anopia type, meaning absence of that type of colour.
(08:40):
Interestingly enough, dogs are dichromatic.
They see mostly blue and yellow.
So what a person with red-green colour blindness sees.
Pointless fact aside. Monochromacy.
With this kind, you either have one type of cone or no cones at all.
So you have limited ability to see colour, often seeing in shades of grey.
These categories can be further broken down into the more specific colour blindness types.
(09:02):
In red-green colour blindness, there are several categories.
These include protanopia.
This is when the L cones are missing, so you are unable to see the colour red.
With this, you will mostly see shades of blue and gold and can confuse red with black.
You may also confuse dark brown with other various dark colours like dark green, red
or orange.
Deuteranopia.
In this form, the M cones are missing, so you are unable to see the colour green.
(09:26):
You will mostly see in shades of blue and shades of gold.
With this, you may confuse some shades of red with some shades of green and also some
shades of yellow with bright shades of green.
Protanomaly.
With this type, you still have all three cones, but your L cones are less sensitive to red
light.
So red may appear as a dark grey and colours that contain red may appear less bright.
(09:47):
Deuteranomaly.
In this type, you also have all three cones, but your M cones are less sensitive to green.
So you will mostly see in blues and yellows and colours will appear more muted.
With blue-yellow colour vision defects, there are (09:58):
tritanopia.
This form, there is an absence of the S cones, so you can't perceive blue light.
With it, you will mostly see reds, light blues, pinks and lavender.
Yes, that does sound a little odd, but that is correct.
Tritanomaly.
In this type, the S cone is still there, but they are not as sensitive to light.
So with this, blues will look green and you will see little to no yellow.
(10:21):
There are also the monochromacy forms of colour blindness.
These are blue cone monochromacy.
In this form, your L and M cones don't work.
Only your S cones do.
With this, you will struggle to tell the difference between colours, seeing everything in mostly
shades of grey.
This form can also cause other eye issues.
Rod monochromacy, also known as achromatopsia.
(10:41):
This form, most of the cones are missing or do not work correctly.
Everything is in shades of grey.
It also can cause other eye issues.
So what are the genetics behind colour blindness?
This will depend on the type of colour vision deficiency.
For those with red-green colour blindness, which is the most common form, it is inherited
in an X-linked recessive form.
So the mother can be a carrier without knowing and with a faulty gene, she has a 50-50 chance
(11:04):
of having a son who is red-green colour blind or who does not possess the trait.
She also has a 50-50 chance of passing the trait on to an asymptomatic daughter who would
also be a carrier.
This is caused by a change in either the OPN1LW or the OPN1MW genes.
For those with blue-yellow colour blindness, this is inherited in a different pattern.
(11:25):
This is an autosomal dominant pattern.
So you need one copy from the affected parent to also have this condition.
Blue-yellow colour vision defects are caused by the OPN1SW gene mutations.
In either type, it can lead to changes in the cells in the eyes, specifically the colour
sensitive cells known as the cone cells.
These cells in those who are affected by colour vision defects may either be missing or less
(11:48):
sensitive to light they are supposed to be picking up.
This leads to the colour being perceived differently due to incorrect information being sent to
the brain about what you are seeing.
There is also achromatopsia.
This is an absence or near absence of colour vision.
This is inherited in an autosomal recessive pattern.
So you need two copies of a mutated gene, one from each parent to display symptoms.
(12:10):
These mutations can occur in several genes.
These genes are the CGA3 gene, CNGB3 gene, GNAT2 gene, PDE6C gene, and the PDE6H gene.
With these mutations, they prevent the cone cells in the eye from reacting appropriately
to light.
For those with incomplete achromatopsia, they have some cone function.
(12:33):
For those with complete achromatopsia, the cone cells do not function and all vision
is from the rod cells in the eye, which is what is normally used for low light or night
vision.
How do we test for colour blindness?
The most common test for colour blindness or colour vision defects is the Ishihara tests.
This as I mentioned before is the plates of coloured spots that have a number in them,
but in the case of testing young children it is normally a shape.
(12:55):
This can be done in children as young as 4.
Depending on the plate, some of them you can only see with full colour vision or trichromacy,
others have numbers you can only see with some form of colour vision deficiency.
Based on the results, several things may be recommended.
These include more extensive eye testing and genetics testing.
These can be done to determine the severity of the colour vision deficiency and what is
the cause.
(13:16):
We will get right into the symptoms and presentation right after this little break.
If you have been enjoying this episode, you can check out the notes on our Buy Me A Coffee.
What symptoms might your child have if they had colour blindness?
(13:38):
This will depend on the specific kind of colour blindness.
For those who have red-green colour blindness, they will struggle to differentiate between
red and green.
For those with yellow-blue colour blindness, they will have a difficulty with differentiating
between yellow and blue.
This will depend on the severity as some with more mild versions would have less difficulty
than others.
No person with these conditions is the same as another.
There is also another form of blindness that causes an absence of colour vision.
(14:01):
So they are unable to see colour, they will see in shades of blacks, greys and white.
The easiest way to picture this is if you have ever seen a black and white film, their
vision would be similar.
This type of colour vision may be called achromatopsia.
So an inability to see colour at all and inability to distinguish any colours is also a symptom
of this.
What should a doctor be aware of when it comes to colour blindness?
(14:22):
There are several things a doctor should be aware of when it comes to colour blindness.
These include other eye conditions.
For those with achromatopsia, they can have other problems with their vision.
These include nystagmus, which is a rapid back and forth eye movement, photophobia,
which is an increased sensitivity to light.
They may also have farsightedness, which is hyperopia, or less commonly nearsightedness,
(14:42):
which is myopia.
All of these develop in the first few months of life.
You should also be aware that colour vision can be affected later in life by several things.
These include disease.
Various illnesses and diseases can affect the colour vision.
These include sickle cell anaemia, which was covered in episode 15, glaucoma, Alzheimer's
disease, which we discussed in episode 46, chronic alcoholism, multiple sclerosis, which
(15:05):
is episode 34 for those who are curious, diabetes, which is episode 26, macular degeneration,
Parkinson's disease
If you want to learn more, check out episode 30 and leukaemia, which is episode 32.
With these conditions, colour vision can be affected.
In some of them, one eye is more affected than the other, and it can be reversible or
get better with treatment of the underlying cause.
Medicines.
(15:25):
In some cases, medications can affect colour vision.
An example of this is hydroxychloroquine.
In some cases, this can affect colour vision when taking it.
Damage to the eye.
Colour vision can also be affected if the eye is damaged.
This can be through an eye injury, surgery, radiation therapy, or laser treatment to the
eye.
How do we treat colour blindness?
Colour blindness is not a treatable condition.
(15:46):
You might have seen those videos online where people with colour blindness try on those
special glasses.
That only works in certain cases, normally in cases of anomalous trichromacy.
So you have all three kinds of cones, but one isn't as sensitive as the others.
These glasses increase the contrast between colours, making it easier to differentiate,
but they do not provide the ability to see new colours.
(16:07):
So if you see in greyscale and put them on, you will still see in greyscale.
These are still a great tool for those with colour blindness because they do increase
the contrast.
Are there any famous people who have colour blindness?
There are actually quite a few.
One of them is Eddie Redmayne.
He is the British actor who has starred in many films, like The Theory of Everything.
He has red-green colour blindness.
He has discussed it in several interviews and often gets assistance from his wife when
(16:29):
it comes to colours and outfit choices.
If you'd like to check out a social media page, there is Natasha Caudill.
She has achromatopsia.
She uses her social media to show you what her world looks like from her eyes.
It also provides a lot of insight into what it is like living with colour blindness.
I have linked her Instagram in the resources if you are interested.
There are not really any foundations that focus on colour blindness, however your local
(16:51):
vision impairment and blindness charities will most likely have resources for those
with colour vision defects.
If you want to check out the sources, social media links or any other links you can head
to Anatomyofillness.com.
If you enjoyed this episode and would like to hear more, subscribe to be notified about
our latest episodes.
If you would like to join our community, you can join us on Discord or Instagram.
You can also catch us on YouTube for more great content.
Otherwise stick around for the next episode.
(17:26):
Did you know colour blindness is surprisingly common?
300 million people worldwide are estimated to have the condition.
This is roughly 1 in 12 men and 1 in 200 women.
98% of people with colour blindness have some form of red-green colour blindness.
Another interesting little tidbit, babies are actually born colour blind and have pretty
poor vision.
Colour vision is normally fully developed by 6 months of age.
During a pick up from preschool for your little boy Oliver, his teacher pulled you aside and
(00:04):
you braced yourself, thinking he had potentially gotten himself into trouble again with his
cheekiness.
But to your surprise, her inquiry took a different turn.
Have you noticed Oliver struggling with colours at home?
She asked.
Her brow furrowed with genuine concern.
Your mind raced.
Colours?
Surely he knew red from green, right?
Confused you asked what she meant by that.
(00:24):
And she explained that during their lessons on colours, he was unable to differentiate
between some of them.
Intrigued and a bit concerned, you decided to test him at home and quickly discovered
he indeed struggled with recognising certain colours.
This has led you to the decision to schedule an eye test for him.
(00:55):
Hello and welcome to Anatomy of Illness.
Today's episode is about colour blindness.
Before we get into the condition, we are going to start with the history.
So why do we know colour blindness exists?
We begin in 1794.
This is when John Dalton would describe his and his brother's colour blindness.
Dalton was a respected physicist and chemist during his time.
He found that he often mistook red for green and pink with blue.
(01:17):
He would compare his vision with others using a book of silk threads in an attempt to understand
how others perceived the world.
John Dalton came to the conclusion that there may have been an abnormality in his eyes causing
his perception of the world to be different.
He suggested that the vitreous humour, which is the fluid in the eye, was different.
He believed that his had a blue tint, or he had some sort of pre-retinal filter.
(01:38):
Dalton in his will requested an autopsy be performed on his eyes to see if his theory
was correct.
This autopsy was performed in 1844 by Joseph Ransome, who was his medical attendant.
In this examination of his eyes, he collected the humour from one of them to examine it.
It was completely normal, there was no blue tint.
He removed the lens of one eye and examined it.
(02:00):
The lens did have some yellowing, but this was not from colour blindness, this was actually
due to the ageing of the eye.
Dalton had reached the age of 78, so his eyes were naturally deteriorating.
Ransome also cut off the posterior pole of the eye, so the very back of the eye, and
looked through it.
He noted that there was no colour distortion for scarlet or green objects when observed
through the part of the eye, like Dalton believed there would have been.
(02:23):
Ransome did not get rid of his superior's eyes, no he stored them in air.
Interestingly enough, DNA was later taken from these and tested.
Dalton's theories were incorrect on what could be causing his Daltonism.
Yes, this was what they were calling colour blindness at the time.
The other theory that was popular at the time was that there was a defect in the brain.
Interestingly enough, what was written on the autopsy of John Dalton, is that his Daltonism,
(02:47):
or colour blindness in today's terms, was caused by deficient development of the phrenological
organ of colour.
This was corresponded to part of the frontal lobe.
Phrenology is a no longer used science I have covered on our YouTube channel, which you
can check out.
This measured the bumps and dips in a person's skull, equating it to a person's traits.
The frontal lobe does not affect a person's colour vision, nor does it correspond to vision
(03:09):
at all.
You have to go to the back for that, the occipital lobe.
Now we move back to 1785, just for a little bit.
With a publication in a general German science magazine.
In this there was a theory pushed forward by a person named Giros von Gentilly.
They claimed that there were three types of membrane, or molecules, in the retina corresponding
to the three types of light.
(03:30):
Colour blindness would occur when one or two of these three kinds of molecule or membrane
were either paralysed or overactive.
This theory may have helped Thomas Young, who combined the idea of the three receptor
theory and the physical hue as a continuous variable.
He used this to explain Dalton's colour blindness.
He claimed the absence or paralysis of those fibres of the retina, which are calculated
(03:51):
to perceive red, were to blame for his colour blindness.
Moving forward to 1855, with the arrival and end of the industrial revolution.
We had many new inventions.
One of these being trains.
Now why would a medical podcast care about trains?
Well with trains we inevitably have train accidents.
In 1855 colour blindness was viewed as potentially dangerous and as a threat to life.
(04:14):
This is evident in the publication by Edinburgh Professor of Technology, George Wilson.
This publication was titled, Researches on colour blindness with a supplement on the
danger attending the present system of railway and marine coloured signals.
This would not be the only train based colour blindness crossover.
There were actually many railway accidents linked to colour vision defects leading to
(04:37):
the unease from the era to even leak into the literature.
This is highlighted in the work of Charles Dickens, more specifically his 1866 short
story The Signal Man.
This came out about a year after he was involved in a fatal train crash, the Staplehurst rail
crash.
More specifically.
In this book colour blindness is alluded to, with his anxiety towards the red light.
(04:58):
As the apparitions he sees linked to the deaths are linked to the red signal light.
It indicates the characters sense of sight was impaired.
Moving away from Dickens and to 1875 we meet physiologist Frifthiof Holmgren.
He linked a railway workers inability to distinguish between red and green signals to a fatal crash
that occurred in Sweden.
This would lead Holmgren to actually create a test for colour blindness.
(05:21):
He had test subjects match little skeins of wool.
So skeins is just like a little group of threads.
Trains were not the only form of transport affected, no.
Don't worry boats were affected too.
Not the Titanic though, that was an iceberg.
This is evident in the 1895 writings of an ophthalmologist by the name of Thomas H. Bickerton.
“It is now no uncommon thing to hear of officers being dismissed for colour blindness, who
(05:43):
have held in some cases for years lucrative and responsible appointments on board ships.”
Ship workers and railway workers could be fired for colour blindness or abnormal vision.
Or in some cases they were exploited by others who threatened to reveal their defect, if
this was found out.
This is also evident in the literature from the time.
In the 1902 short story by Joseph Conrad, who was actually a sailor prior to being an
(06:04):
author, this story is called The End of the Tether.
In this story the main character, who is an aging skipper, hides a visual defect from
the ship's owner.
He finds out and begins exploiting him.
The story does not directly mention colour blindness, however when the first mate finds
out about the main character's condition, he experiences symptoms out of sympathy.
Examples of this in the book are, “the sun had turned blue” and “the very colour of the
(06:28):
sea seemed changed.”
Moving to 1917 and sailing all the way to Japan to meet Shinobu Ishihara.
Dr Ishihara was an ophthalmologist, who invented the Ishihara tests.
If you have ever seen those colourful spotty circles with a number in them, then you have
seen an Ishihara test.
This test was initially developed for the Japanese military, as he was a doctor for
(06:49):
them, when he created it in 1916.
But in 1917 it became widespread.
These are a common test still used today to determine colour vision defects.
If you are enjoying this episode and think someone else might enjoy it or find it valuable,
make sure to share it with them.
It helps us grow and helps us keep the lights on.
So what causes colour vision?
Colour vision is caused by cone cells in the eyes.
(07:09):
These come in three types.
Red sensing cone cells, also known as L-cones.
These sense the long wavelengths of light, so around 560 nanometres.
Green sensing cone cells, also known as M-cones, they sense the middle wavelengths.
These are around 530 nanometres.
And finally the blue sensing cones, known as the S-cones.
(07:30):
They sense the short wavelengths of light, which are around 420 nanometres.
For the majority of people, these are all present and work normally.
This is colour vision or trichromacy.
Speaking of colour, did you know we have a great colour selection of merch on our website
merchanatomy.com?
Anyway, back to the eyes.
For those who do not have all of these present or they do not work correctly, they will have
(07:52):
some form of colour blindness.
What are the types of colour blindness?
The categories that directly talk about how many cones are present are (07:56):
anomalous trichromacy.
So in this form, all of the cones are still present, but one isn't as sensitive to light
as it should be.
In this type, you don't see colours in the traditional sense.
In the mild form, you may confuse pale and muted colours.
In severe cases, you may confuse more vivid colours.
These are the types that normally end in anomaly.
(08:18):
Essentially, it means partial vision of a specific colour. Dichromacy.
In this type, one kind of cone is missing.
So you have only two kinds of functional cones.
So you are only able to see the world through those wavelengths of light.
With this kind, it is often hard to tell the difference between vivid colours.
This is the anopia type, meaning absence of that type of colour.
(08:40):
Interestingly enough, dogs are dichromatic.
They see mostly blue and yellow.
So what a person with red-green colour blindness sees.
Pointless fact aside. Monochromacy.
With this kind, you either have one type of cone or no cones at all.
So you have limited ability to see colour, often seeing in shades of grey.
These categories can be further broken down into the more specific colour blindness types.
(09:02):
In red-green colour blindness, there are several categories.
These include protanopia.
This is when the L cones are missing, so you are unable to see the colour red.
With this, you will mostly see shades of blue and gold and can confuse red with black.
You may also confuse dark brown with other various dark colours like dark green, red
or orange.
Deuteranopia.
In this form, the M cones are missing, so you are unable to see the colour green.
(09:26):
You will mostly see in shades of blue and shades of gold.
With this, you may confuse some shades of red with some shades of green and also some
shades of yellow with bright shades of green.
Protanomaly.
With this type, you still have all three cones, but your L cones are less sensitive to red
light.
So red may appear as a dark grey and colours that contain red may appear less bright.
(09:47):
Deuteranomaly.
In this type, you also have all three cones, but your M cones are less sensitive to green.
So you will mostly see in blues and yellows and colours will appear more muted.
With blue-yellow colour vision defects, there are (09:58):
tritanopia.
This form, there is an absence of the S cones, so you can't perceive blue light.
With it, you will mostly see reds, light blues, pinks and lavender.
Yes, that does sound a little odd, but that is correct.
Tritanomaly.
In this type, the S cone is still there, but they are not as sensitive to light.
So with this, blues will look green and you will see little to no yellow.
(10:21):
There are also the monochromacy forms of colour blindness.
These are blue cone monochromacy.
In this form, your L and M cones don't work.
Only your S cones do.
With this, you will struggle to tell the difference between colours, seeing everything in mostly
shades of grey.
This form can also cause other eye issues.
Rod monochromacy, also known as achromatopsia.
(10:41):
This form, most of the cones are missing or do not work correctly.
Everything is in shades of grey.
It also can cause other eye issues.
So what are the genetics behind colour blindness?
This will depend on the type of colour vision deficiency.
For those with red-green colour blindness, which is the most common form, it is inherited
in an X-linked recessive form.
So the mother can be a carrier without knowing and with a faulty gene, she has a 50-50 chance
(11:04):
of having a son who is red-green colour blind or who does not possess the trait.
She also has a 50-50 chance of passing the trait on to an asymptomatic daughter who would
also be a carrier.
This is caused by a change in either the OPN1LW or the OPN1MW genes.
For those with blue-yellow colour blindness, this is inherited in a different pattern.
(11:25):
This is an autosomal dominant pattern.
So you need one copy from the affected parent to also have this condition.
Blue-yellow colour vision defects are caused by the OPN1SW gene mutations.
In either type, it can lead to changes in the cells in the eyes, specifically the colour
sensitive cells known as the cone cells.
These cells in those who are affected by colour vision defects may either be missing or less
(11:48):
sensitive to light they are supposed to be picking up.
This leads to the colour being perceived differently due to incorrect information being sent to
the brain about what you are seeing.
There is also achromatopsia.
This is an absence or near absence of colour vision.
This is inherited in an autosomal recessive pattern.
So you need two copies of a mutated gene, one from each parent to display symptoms.
(12:10):
These mutations can occur in several genes.
These genes are the CGA3 gene, CNGB3 gene, GNAT2 gene, PDE6C gene, and the PDE6H gene.
With these mutations, they prevent the cone cells in the eye from reacting appropriately
to light.
For those with incomplete achromatopsia, they have some cone function.
(12:33):
For those with complete achromatopsia, the cone cells do not function and all vision
is from the rod cells in the eye, which is what is normally used for low light or night
vision.
How do we test for colour blindness?
The most common test for colour blindness or colour vision defects is the Ishihara tests.
This as I mentioned before is the plates of coloured spots that have a number in them,
but in the case of testing young children it is normally a shape.
(12:55):
This can be done in children as young as 4.
Depending on the plate, some of them you can only see with full colour vision or trichromacy,
others have numbers you can only see with some form of colour vision deficiency.
Based on the results, several things may be recommended.
These include more extensive eye testing and genetics testing.
These can be done to determine the severity of the colour vision deficiency and what is
the cause.
(13:16):
We will get right into the symptoms and presentation right after this little break.
If you have been enjoying this episode, you can check out the notes on our Buy Me A Coffee.
What symptoms might your child have if they had colour blindness?
(13:38):
This will depend on the specific kind of colour blindness.
For those who have red-green colour blindness, they will struggle to differentiate between
red and green.
For those with yellow-blue colour blindness, they will have a difficulty with differentiating
between yellow and blue.
This will depend on the severity as some with more mild versions would have less difficulty
than others.
No person with these conditions is the same as another.
There is also another form of blindness that causes an absence of colour vision.
(14:01):
So they are unable to see colour, they will see in shades of blacks, greys and white.
The easiest way to picture this is if you have ever seen a black and white film, their
vision would be similar.
This type of colour vision may be called achromatopsia.
So an inability to see colour at all and inability to distinguish any colours is also a symptom
of this.
What should a doctor be aware of when it comes to colour blindness?
(14:22):
There are several things a doctor should be aware of when it comes to colour blindness.
These include other eye conditions.
For those with achromatopsia, they can have other problems with their vision.
These include nystagmus, which is a rapid back and forth eye movement, photophobia,
which is an increased sensitivity to light.
They may also have farsightedness, which is hyperopia, or less commonly nearsightedness,
(14:42):
which is myopia.
All of these develop in the first few months of life.
You should also be aware that colour vision can be affected later in life by several things.
These include disease.
Various illnesses and diseases can affect the colour vision.
These include sickle cell anaemia, which was covered in episode 15, glaucoma, Alzheimer's
disease, which we discussed in episode 46, chronic alcoholism, multiple sclerosis, which
(15:05):
is episode 34 for those who are curious, diabetes, which is episode 26, macular degeneration,
Parkinson's disease
If you want to learn more, check out episode 30 and leukaemia, which is episode 32.
With these conditions, colour vision can be affected.
In some of them, one eye is more affected than the other, and it can be reversible or
get better with treatment of the underlying cause.
Medicines.
(15:25):
In some cases, medications can affect colour vision.
An example of this is hydroxychloroquine.
In some cases, this can affect colour vision when taking it.
Damage to the eye.
Colour vision can also be affected if the eye is damaged.
This can be through an eye injury, surgery, radiation therapy, or laser treatment to the
eye.
How do we treat colour blindness?
Colour blindness is not a treatable condition.
(15:46):
You might have seen those videos online where people with colour blindness try on those
special glasses.
That only works in certain cases, normally in cases of anomalous trichromacy.
So you have all three kinds of cones, but one isn't as sensitive as the others.
These glasses increase the contrast between colours, making it easier to differentiate,
but they do not provide the ability to see new colours.
(16:07):
So if you see in greyscale and put them on, you will still see in greyscale.
These are still a great tool for those with colour blindness because they do increase
the contrast.
Are there any famous people who have colour blindness?
There are actually quite a few.
One of them is Eddie Redmayne.
He is the British actor who has starred in many films, like The Theory of Everything.
He has red-green colour blindness.
He has discussed it in several interviews and often gets assistance from his wife when
(16:29):
it comes to colours and outfit choices.
If you'd like to check out a social media page, there is Natasha Caudill.
She has achromatopsia.
She uses her social media to show you what her world looks like from her eyes.
It also provides a lot of insight into what it is like living with colour blindness.
I have linked her Instagram in the resources if you are interested.
There are not really any foundations that focus on colour blindness, however your local
(16:51):
vision impairment and blindness charities will most likely have resources for those
with colour vision defects.
If you want to check out the sources, social media links or any other links you can head
to Anatomyofillness.com.
If you enjoyed this episode and would like to hear more, subscribe to be notified about
our latest episodes.
If you would like to join our community, you can join us on Discord or Instagram.
You can also catch us on YouTube for more great content.
Otherwise stick around for the next episode.
(17:26):
Did you know colour blindness is surprisingly common?
300 million people worldwide are estimated to have the condition.
This is roughly 1 in 12 men and 1 in 200 women.
98% of people with colour blindness have some form of red-green colour blindness.
Another interesting little tidbit, babies are actually born colour blind and have pretty
poor vision.
Colour vision is normally fully developed by 6 months of age.
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