What is Color Blindness

What is Color Blindness

Color blindness is the inability to distinguish certain color shades.

What are types of color blindness

There are two types of color blindness:

1) Total Color Blindness(T-total), also known as “monochromacy”: This means that a person has no ability whatsoever to tell any colors apart, or even see colors at all. For example, if you were colorblind, the image below would appear completely white.

2) Partial Color Blindness(P-partial): This is when some colors can be distinguished from others – but not fully. A partially color blind person may have difficulty telling reds and greens apart, or orange and aqua apart. Even though they can’t tell them apart fully, they may still be able to discriminate some colors. For example, the image below may appear bluish-grey for a partially color blind person.

First of all, I want to make it clear that I am not colorblind and these are the simple assumptions that lead me to this theory. In this article, I will try my best to explain different factors on how one can become colorblind and what might have been going through in past during the pregnancy/birth stage of a person.

1) Chromosomes:

Normal human beings have 23 pairs of chromosomes, each one comes with two chromatids (one from each parent). A chromosome is a structure made up of DNA and protein where DNA gets replicated into its daughter cells so they can divide. Because chromosomes are made up of proteins, there are numerous allergies people suffer from.

Each color vision defect is linked to a different chromosome. So it might be possible that differences in chromosomes may cause the same difference in perception of colors by an individual. To make this clear let’s consider the image below:

We all know that we have two eyes and each eye perceives things differently based on what we see. Based about 100 million photoreceptors(cones) present at the backside of our eyes work as transmitters and they convert light into an electrical signal and send them to the brain which then resolves them into something meaningful for us humans to perceive. It was thought that everyone has an equal amount of cones so people with normal vision can distinguish between separate wavelengths of light(red, green, blue, etc.).

2) Retinas are made up of 3 layers namely:

– The innermost layer is called the “ganglion cell layer”. It is made up of bipolar cells and terminal cells. There are two types of bilsiparidal cells – ON-bipolar(respond to light hitting the retina) and OFF-bipolar(do not respond to light). This layer converts the electrical signal into chemical signals.

3) The middle layer is called the “plexiform layer”.

It consists of several neuron-like cells which are made up of different proteins. The neurons in this layer are connected, but not directly to the ganglion cells. These neurons detect electrical signals from the bipolar cells and convert them into chemical signals. Now comes an important part.

For normal vision, different amount of cones present at the backside of the eye send their output to these plexiform layers at the backside to the brain through bipolar cells so that when the light hit the retina goes ON, communication is sent toward the cortical area for processing.

But sometimes when there are only a few or no cones present in any retina or both retinas due to some reason then the communication is not properly sent to the brain. So that proper communication can’t be made by the retina to ganglion cells, so unbalance in chemicals signals are sent toward brain which eventually becomes unbalance in the overall chemistry of the body which causes color blindness.

4) The third layer is called the “ganglion cell layer”. It contains neurons that connect directly with bipolar cells and terminal cells(which convert the electrical signal into chemical signals). Now, these neurons send universal data toward the brain through the optic nerve for processing.

So this was just a rough description of how our eyes work, if you want more detailed information you can visit Wikipedia or any other site.

Color blindness types:

There are two groups of color blindness namely…

– Dichromacy:- Monochromacy refers to an eye that can only detect one wavelength of light. They are called dichromats because they have two different types of cone cells(one with a peak response at 420 nm and the other with a peak response at 580nm). But they cannot distinguish between any colors in between those two peaks, thus all colors appear the same for them.

 Anomalous trichromacy:

All people with normal color vision are trichromats – this means that their retina contains three different types of single cones, each with slightly different peak sensitivity (red: 564 nm; green: 530 nm; blue: 436 nm).

With these three pigments combined, most likely in the right proportions, the brain can perceive up to a million different hues. Anomalous trichromacy means that one of the three channels is altered, and as such people with this type of color blindness see less distinct colors than those with normal vision.

Common types:

– Red-green color blindness: Less than 1% of all males suffer from this type of color blindness where they can’t distinguish between red and green color. But they are not unable to differentiate them completely, only the contrast between them is lowered or they look the same for them.

So these people can easily differentiate between blue and yellow color compared to red and green. This happens because in anomalous intricacy when there is a decrease in sensitivity of either green or red cone then as a result, people can’t distinguish between any colors which have low information content.

Blue-yellow color blindness:

It is a very rare type of color blindness where they can’t even differentiate between blue and yellow color. The reason for this is the same as above because when the sensitivity of both red and green cones are decreased then all colors with high information content look the same to them. Because these two colors have the highest information value among the other six basic hues.

What’s the difference between protanopia, deuteranopia, and tritanopia?  

– In protanopia, there is only one type of cone present at the retina which peak sensitivity wavelength is missing so that it send unbalanced information toward the brain, which leads to the inability of differentiating between colors such as red and green.

– In deuteranopia two cone cells are present at the retina but the peak sensitivity wavelength of one is missing so that information sent toward the brain is unbalanced, which leads to the inability to differentiate between colors such as yellow and green.

So these people can’t tell the difference between blue and violet color either because both have high information values. – In tritanopia, three types of cone cells are present at the retina but the peak sensitivity wavelength of all are missing so that messages send toward the brain are highly unbalanced which again results in difficulty in differentiating between colors.