Color Blindness - Types, Causes, Symptoms, Diagnosis and Prevention.


Introduction


color blindness



"Every color has a different story, but not everyone can see it." - Anonymous

Color blindness or color deficiency is the inability to see the colors in the normal way or it is the reduced inability to distinguish between certain colors. Color blindness does not mean you cannot see any color or you see only shades of grey. Color blindness usually is genetic, it is passed on through the genes. It can also result from physical or chemical damage to the eye or the optical nerve or different parts of the brain.





Generally, males are more affected than the females. Prevent Blindness has stated that around 8% of males and less than 1% of females have color blindness.

Usually, color blind people have difficulty in distinguishing certain colors such as blue and yellow or red and green.

Most people who are color blind adjust and have little difficulty in going around with everyday activities. Special glasses and contact lenses sometimes are used by color blind people to see the real colors.


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History of Colorblindness

John Dalton


John Dalton, an English Chemist found out that he was color blind and he himself researched on this. He wrote the first scientific paper in the year 1798 on the subject of color blindness sometimes referred to as Daltonism. The paper was titled, "Extraordinary facts relating to the vision of colors."


John Dalton believed that shortage in the color perception was due to discoloration of aqueous humor in the eyeball. He believed that he had a bluish fluid in his eyeball which filtered off all other colors. He was well known for his early atomic theory. He wanted an autopsy done on his eyes after his death to prove that there was a bluish fluid in the aqueous humor which turned out to be wrong.

Today over 2.7 million people are color blind.



Human eye and Color


Human eye contains specialized cells that respond to light and are called photoreceptor cells. There are two types of photoreceptors in the human eye: Rods and cones.

Rods can work in dim light. Rods do not help with color vision because of which we see everything in gray at night. There are around 100 million rod cells.



Cones are used to see the color and work in bright light. Cones are specialized retinal cells containing pigments with different spectral sensitivities. There are only 6 million cones in human eye. There are 3 types of cones: S - Cones, M- Cones and L - Cones which are sensitive to visible wavelengths of light that correspond to short wavelength, medium wavelength and large wavelength respectively.


The L - cones have peak wavelength ranging from 564 - 580 nm, M - Cones ranging from 534 - 545 nm and S - Cones ranging from 420 - 440 nm . The most common cause of color blindness is an inherited problem in the development of any of these three cone cells.



Types of Color Blindness



Red and green is one of the most common type of color blindness which is followed by blue - yellow color blindness and complete color blindness. Different types of color blindness causes problems in seeing different colors.



1. Red - Green Color Blindness


There are four different types of red and green color blindness. They are all commonly inherited forms of red - green color blindness. People with this type of defect have trouble recognizing colors of red and green due to the absence or mutation of red and green retinal photoreceptors.

  • Deuteranomaly is a type of red and green color blindness in which green looks more red and hence is also called green blind. Usually in the evening dark green objects appear black to such people. This is usually mild and does not affect everyday activities. Peak of sensitivity green cones are moved towards the red sensitive cones resulting in sensitivity of the green area of the spectrum.

  • Protanomaly is a rare form of color blindness making 1 % of the male population as it is carried on by the X chromosome. In this type the L- cones are defective and they appear in different intensities. The ones suffering from this type are less sensitive to red light than the normal. They are unable to distinguish colors and are unable to see mixed lights having same colors. The red end of the spectrum is darkened in such people and hence they mistake red for black.

  • Protanopia is similar to protanomaly. The only difference is that here the L - cones are completely missing. People with this type of defect lack in red L -cones and are unable to distinguish between colors in the green - yellow - red spectrum. There is such a lot of dimming of the red wavelength that red is confused with black or dark grey and hence they find it difficult in following traffic signal as for them red traffic lights appear to be completely extinguished. Violet, lavender and purple look all similar as the red part in these colors is dimmed.

  • Deuteranopia lack green M - cones. The ones affected cannot distinguish colors in the green - yellow - red section of the spectrum. This form of color blindness is also known as Daltonism named after John Dalton who was also suffering from Deuteranopia which was found out after 150 years of his death by analyzing the DNA of his preserved eyeball. The ones suffering with deuteranopia can see wavelengths shorter than 498 nm as blue and longer than it as yellow.



2. Blue - Yellow Color Blindness


People with blue - yellow color blindness often cannot distinguish between blue and green as well as yellow and red. Gene coding for the blue receptor lies in chromosome 7 which is present in both males and females and hence is shared equally by men and women. The DNA sequence is isn't similar which means that this type is not congenital as the red - green color blindness. The different types of blue - yellow color blindness are:

  • Tritanopia lacks S - cones. This affects less than 1% of males and females. Those affected see blue, indigo and spectral violet as green color. Some of these colors are even seen as black. Yellow cannot be distinguished from pink and purple and are often seen as various shades of red. It also makes colors look less bright.

  • Tritanomaly is an equally rare form in males and females present in about 0.01% of them. In this the S - cone is shifted towards the green part of the spectrum. It is a mutated form of the blue pigment. It is shorter than 570 nm.



3. Total Color Blindness

Total blindness

The inability to see color is called as total color blindness. It usually refers to congenital color vision disorders. When only a single channel conveys information about color it is called as monochromacy which is linked to total color blindness.


Monochromacy has two primary forms.

  • Rod Monochromacy also called as achromatopsia is a condition in which retina does not contain any cone cells. This results in difficulty of vision in lights with normal intensity along with absence of discrimination in colors.

  • Cone Monochromacy is the condition in which rods and only a single cone is present. They either have L - cones or M - Cones and S - Cones are either inactive or absent. People with such condition have a normal vision in daylight but will not be able to distinguish hues.

  • Blue - Cone Monochromacy is the condition in which only S - Cones or rods are transmitting color or brightness information. It is caused by the loss or rearrangement of L - cones and M - Cones.




Causes of Color blindness


causes of color blindness

Color blindness is caused by a genetic condition which depends on how the S - Cones, M - cones, L - Cones respond to light. The gene responsible for this condition is usually carried on by the X chromosome and hence men are affected largely compared to women.


A female has two X chromosomes and a male has a X and a Y Chromosome. For a female to be color blind it must be present on both her X chromosome and if a woman has only one color blind gene, she will be a carrier of color blindness but won't be color blind herself. Male cannot be a carrier of chromosome to the son as X chromosome can be transferred through the male only to the daughter.

Sometimes we get color blind in the later part of our lives even if we are not born color blind due to the following reasons:

  • Trauma which could affect the optic nerve or retina.

  • Illicit drugs and even some prescribed medicines also may cause color blindness.

  • Medicines like digoxin, ethambutol, chloroquine, hydroxychloroquine and phenytoin, sildenafil or viagra cause color blindness as a side effect.

  • Chronic alcoholism also sometimes causes color blindness.

  • Diseases like metabolic disease, sickle cell anemia, glaucoma, macular degeneration, Alzheimer's disease, Parkinson's disease, Leukemia, achromatopsia, etc. cause color blindness.

  • Chemical exposure may also cause color blindness. Carbon di sulphide and styrene are some chemicals which affect the color vision.

  • Some inherited disease like cone dystrophy, cone - rod dystrophy, retinitis pigments, retinoblastoma, Liber's congenital amaurosis, shaken baby syndrome and inflammation of the optic nerve can also cause color blindness.

  • Aging also is a cause for deterioration in color vision.



Symptoms of Color Blindness


Symptoms of color blindness


Color blindness is usually first identified by the parents of the child. The common symptoms of color blindness are:

  • Difficulty in distinguishing the colors.

  • Inability to see the shades of the same color. This happens usually with red and green or blue and yellow.

  • Inability to say how bright the colors are.


People with mild or moderate color blindness may get used to the colors they see around them or learn the colors as it is told to them in the childhood. For example, children are taught that grass is green and hence they feel that the color they are seeing itself is green and don't realize that it is not green color which is visible to them. Some tend to live with the same and hence may not even know that they are color blind. People with severe color blindness might have symptoms like -

  • side to side eye movements or nystagmus.

  • Photophobia or light sensitive eyes.

Nystagmus is a condition in which there is involuntary movement of the eyes, often called as the "dancing eyes" whereas photophobia is a condition in which the eye is sensitive to bright light and leads to discomfort in the eyes.


Diagnosis of Color Blindness


Diagnosis of color blindness

Color blindness has to be diagnosed at an early age as this would affect the child's performance in school and may affect the child's confidence at a very early age and in adults it may affect their career and may seem very difficult in handling it at times.



  • The most common test done to diagnose color blindness is the Ishihara Plate Test. It was introduced by Dr. Shinobu Ishihara from Japan. It is a color perception test usually done for red - green color blindness but cannot be done for blue - yellow color blindness. Several plates or pages will be presented before the patient in which each page will have a circle created dots composed of two or more colors and a number is hid in between the colored dots. The optometrist asks the patient to see which number is seen on the plate. People suffering from red - green color blindness will have trouble seeing some of the numbers.

  • Cambridge Color test is similar to Ishihara blood test. The only difference is that instead of the plates or pages the numbers are displayed on the computer screen with different colored backgrounds and the letter C is asked to be picked which pops up randomly and when seen the patient has to press any four keys.

  • Anomaloscope Color Blindness Test is used to check the red - green color blindness. A circle is seen through the eyepiece of the anomaloscope which is having two different colors. A knob is rotated to match the two different colors in both brightness and color.

  • Farnsworth-Munsell 100 hue test measures the ability to determine precise changes in color. It is based on 88 colored plates and not 100 as the name suggests which was introduced by Farnsworth in 1943 Four batches of 22 colored plates is shown and you will be asked to arrange these mixed plates in the correct order. The number of errors decides the color vision deficiency.

  • Farnsworth Lantern Test is a test in which pairs of light are shown and colors have to be identified. The US military and aviation industry use this test to identify or determine the severity of the color blindness.

  • D - 15 Dichotomous Test is a test introduced by Farnsworth in 1947 in which the colors have to be arranged in an order. The person with color blindness cannot arrange the colors as a normal person can do. This test cannot be relied on as it does not determine the severity of the problem.


Prevention of Color Blindness


prevention of color blindness

There is no practical way to prevent color blindness, since most of the one's suffering from color blindness have inherited it from birth. At a later stage of life if we do not want to get affected from color blindness we need to follow healthy lifestyle, get regular eye exams, see your healthcare provider, safeguard ourselves from any trauma or danger, avoid illicit drugs and medicines, avoid drinking a lot of alcohol and lastly try and avoid any type of chemical exposure. Eye exercises can also be done with the guidance of ophthalmologist to prevent color blindness.



Treatment of Color Blindness


There is no cure for congenital color blindness but people with color vision deficiency can learn to recognize color by other means.




  • There are tinted eyeglasses or lens that can help you see or differentiate a few colors. Colored spectacle lenses or lenses that filter certain wavelengths allow people to discriminate a few colors. It may not completely cure the color blindness. In case of acquired color blindness at a later stage of life then doctor can treat the underlying disease or injury.

  • Dr. Harry Zeltzer BS OD is the inventor of X chrom contact lenses. These lenses are monocular corneal contact lens which increases the color perception in those suffering with color vision deficiency.

  • Enchroma glasses are used for mild or moderate color blindness. It usually takes 5 to 15 minutes before the colors are seen differently. These glasses contain optical materials that remove particular wavelengths of light wherever there is overlapping of colors.

  • There are many mobile and computer applications have been developed to help color blind people to better differentiate between colors. Colorblind Pal is an app which helps people who are color blind to see the colors around them and also normal people can see how it is like to be color blind.

  • Friends and family can help remember the order of things rather than the color. For example, the order of traffic lights can be remembered rather than the color so that there would be no problem in driving for color blind people.

  • A device called eyeborg helps people with achromatopsia or total color blindness perceive color through sound waves.

  • At present there is no cure for color blindness but scientists are trying to find a permanent solution for the same. A small trial in Germany, an experimental gene therapy was performed on 9 people, eight men and one woman who were suffering from total color blindness or achromatopsia. After the gene therapy all nine of them could see some color as well as more letters on a vision chart. This gene therapy can be a permanent one - time treatment for color blindness.

  • This gene therapy was developed at Ludwig Maximilian University of Munich and University hospital Tubingen. This involves a genetically engineered virus designed to correct a defect in a gene known as CNGA3. One third of all cases of total color blindness result due to mutations in these genes.

  • The gene therapy has to undergo more trials so as to get completely approved.

  • A gene therapy called Luxturna is already in the market and costs around $425,000 per eye or a total of $850,000 in United States.



Living with color blindness


Coping with color blindness might be difficult. It becomes difficult for color blind people to differentiate between ripe and unripe fruits, finding matching items for clothes, to check if meat is undercooked, etc. Organizing and labelling things may help in some tasks. People with color blindness are good at spatial arrangement. Having a job with color blindness will be difficult so they have to choose a career in which color blindness will not be a negative point.


Conclusion


Color blindness does not mean that those suffering from it cannot see any color but they have color vision deficiency. Color blind people are like handicapped people but cannot be recognized easily by others. A person with color blindness has to be encouraged and dealt with patiently as this is not an acquired disease but is an inherited one in almost 99% of them. Famous personalities like John Dalton and Mark Twain also suffered from color blindness.


camouflage

When we suffer from color blindness, we face lot of negativity, discouragement and embarrassment. We need to always think positive as negativity does not lead us anywhere.

Being color blind has its own advantages. Color blind people are good at effective recognition of color patterns and hence are better in seeing camouflage.


They have the ability to recognize unnatural patterns amidst natural ones. This is a perk to the color blind people. According to some reports color blind people excel as snipers in military. Hence, being color blind does not mean we are not capable of doing anything. We are capable of doing what no one else can do.


Rubix

There is a saying, "Rubix cubes are easy when you are color blind." Life may seem difficult being color blind but not impossible to live a happy life. Stay positive, stay healthy and be colorful with your mind, heart and soul.







References

Research on color blindness reference

Carrier of color blind gene

Research on Cure of color blindness