Types of Colour Blindness — Colour Blind Awareness Protanopia Tritanopia People with dichromatic colour vision have only two types of cones which are able to perceive colour i.e. they have a total absence of function of one cone type. Lack of ability to see colour is the easiest way to explain this condition but in actual fact it is a specific section of the light spectrum which can’t be perceived. For convenience we call these areas of the light spectrum ‘red’, ‘green’ or ‘blue’ . The sections of the light spectrum which the ‘red’ and ‘green’ cones perceive overlap and this is why red and green colour vision deficiencies are often known as red/green colour blindness and why people with red and green deficiencies see the world in a similar way. People suffering from protanopia are unable to perceive any ‘red’ light, those with deuteranopia are unable to perceive ‘green’ light and those with tritanopia are unable to perceive ‘blue’ light. People with both red and green deficiencies live in a world of murky greens where blues and yellows stand out. Browns, oranges, shades of red and green are easily confused.

Both types will confuse some blues with some purples and both types will struggle to identify pale shades of most colours. However, there are some specific differences between the 2 red/green deficiencies. Protanopia Protanopes are more likely to confuse:- 1. Black with many shades of red 2. Dark brown with dark green, dark orange and dark red 2. Some blues with some reds, purples and dark pinks 3. Mid-greens with some oranges Deuteranopes Deuteranopes are more likely to confuse:- 1. Mid-reds with mid-greens 2. Blue-greens with grey and mid-pinks 3. Bright greens with yellows 4. Pale pinks with light grey 5. Mid-reds with mid-brown 6. Light blues with lilac Tritanopes The most common colour confusions for tritanopes are light blues with greys, dark purples with black, mid-greens with blues and oranges with reds. The images show how the beautiful colours of the pigments are lost to people suffering with each type of dichromatic vision.

Monochromacy (achromatopsia) Normal Vision Monochromacy People with monochromatic vision can see no colour at all and their world consists of different shades of grey ranging from black to white, rather like only seeing the world on an old black and white television set. Achromatopsia is extremely rare, occuring only in approximately 1 person in 33,000 and its symptoms can make life very difficult. Usually someone with achromatopsia will need to wear dark glasses inside in normal light conditions. We have had several very concerned people contact us via this website because they or their children have been diagnosed by their optician with ‘total colour blindness’. Although we are unable to advise on the diagnosis of specific cases we have undertaken further research to try and understand why so many people are being told they are totally colour blind when in reality they are much more likely to have a severe form of red-green colour blindness. Our research has revealed that in many cases opticians have only received basic training on colour vision deficiency and some may therefore be incorrectly interpreting the results of the Ishihara tests. If you have been diagnosed as ‘totally’ colour blind please follow the links to these two specialist websites for further information.

If you think you do have the symptoms of achromatopsia ask your optician to refer you to a specialist who can confirm your condition. Statistics There is general agreement that worldwide 8% of men and 0.5% of women have a colour vision deficiency. These figures rise in areas where there is a greater number of white (Caucasian) people per head of population, so in Scandanavia the figures increase to approximately 10-11% of men. By contrast in sub-Saharan Africa there are few colour blind people. Countries such as India and Brazil have a relatively high incidence of colour vision deficients because of the large numbers of people with mixed race genes in their genetic history. The 8% of colour blind men can be divided approximately into 1% deuteranopes, 1% protanopes, 1% protanomalous and 5% deuteranomalous. Approximately half of colour blind people will have a mild anomalous deficiency, the other 50% have moderate or severe anomalous conditions. Numbers of tritanopes/tritanomalous people and achromats is very small, perhaps 1 in 30-50,000 people.

Reliable statistics for people with an acquired form of colour vision deficiency are difficult to find but as many as 3% of the population could be affected because age-related deficiency is relatively common in the over 65s and therefore on the increase in the UK due to the rising numbers of elderly people per capita. To put these statistics in context, an all-boys school in the Home Counties of England with 1000 pupils would have approximately 100 colour deficient students. 12-13 would be deuteranopes, 12-13 would be protanopes, 12-13 would have a form of protanomaly and 62 would have a form of deuteranomaly. About half of those with an anomalous condition would have a moderate to severe form of deficiency. Colour Blindness Best treatment and cure for color blindness online – Artificial Eye Co Both male and female are equally affected The defect of blue colour blindness is carried on a non sex chromosome Are you looking for a job / career where good colour vision is desirable but defective colour vision would not necessarily cause a handicap?

Accountant, Architect, Baker, Beautician, Botanist, Brewer, Butcher, Carpenter, Engineer, Farmer, Florist, Forester, Furrier, Coroner, Jeweller, Librarian, Tanner, Tailor, Milliner, Miner, Nurse, Dental surgeon, Manicurist, Metallurgist, Optometrist, Ophthalmologist, osteopath, Painter, Physician, Potter, Sales person (Garment, Footwear, Glass items, Linen, Cosmetics, Toiletries, Jewellery, Confectioner, Stationer, Storekeeper), Auctioneer, Clothes designer, Cook or chef, Dental technician, Draughtsman, Dressmaker, Geologist, Gemologist, Interior decorator, Interior designer, Interior planner, Grocer, Hair dresser, Horticulturist, Surgeon, Waiter, Zoologist, Physiotherapist, Bacteriologist, Confectioner, Anaesthetist, Chiropodist, Diamond grader, Illuminating Engineer, Instructor of driver, Fishmonger, Gardener and landscape gardener, Media industry (Lighting director of stage show, film, T.V, Beautician of stage show, film, T.V, Pharmacist assistant, Post office counter

 assistant, Shoe repairer - cobbler, Telephone switchboard operator, Theatre props manager, Stage props manager, Window dresser, Driver in public service - bus driver, Builder/Brick Layer, Buyer - textiles, yarn, tobacco, food e.g fruit, Cocoa, timber, Carpet/Lino fitter, planner, Precious stone setter) Recommended colour vision requirement in ceramic Recommended colour vision requirement in Chemical Laboratory Analysis Perfect colour vision Switchboard operator Are you colour blind and you work with resistance and capacitors and you are having any of these problems while at work?

Codes of resistors or capacitors Colour codes of electronic components Pairing colour coded cables and wires Red and orange code looks identical Confusion in between violet and yellow colour Difficulty in distinguishing between green and brown Difficulty in distinguishing between red and brown Difficulty in distinguishing between green and red Difficulty in distinguishing between green and grey Difficulty in distinguishing between grey and brown Difficulty in distinguishing between violet and brown Complete failure to identify the presence of a band Difficulty in identifying colours with matt surfaces or soiled components Future of Colour blinds - In spite of talent and technical knowledge with complete expertise in the professional field many a times colour blindness becomes a barrier and first criteria for eliminating the potential individual from proving his caliber not only in airlines, railways, navy, engineering, medical, law enforcementbut at every level of entry into the professional world. Hopefully this scenario will change in near future with the advancement in the management and treatment of colour blindness. Probable reason for colour blindness could be - The instruction for the development of cone cells are wrong. Cone cells might be missing or less sensitive to light. It may be that the pathway from the cone cells to the brain has not developed correctly. Colour detection and differentiation - The colour are detected by cones which are of 3 types - red, green and blue.

All hues can be produced by mixing red, green and blue light. Most birds are tetra chromats and around 2-2% of world's women are tetrachromats. they have the kind of 4th cone that gives a significant increase in colour differentiation. How to select a career with respect to colour blindness? There are specific guidelines offered by different trade and industry. Individual company and its individual post and designation has its own specific colour related requirement. Here today you will learn more about the requirement of colour vision in different trades and industry. Do you think that being colour blind can be an asset? Strange but true, being colour blind could be a boon . Colour blinds can be of great help in detecting camouflage. Do you know which occupations require perfect colour vision?

Armed forces, Civil aviation, Colour matcher in - Coloured paper industry, Ceramic industry, Dyeing industry, textile industry, Paint industry, Ink industry, Cosmetic industry, Navigation - Pilot, Fisherman, Railways, Carpet industry - Weaver, Spinner, Bobbin winder, Inspector in carpet industry, Electrical industry - Motor mechanic, Electrician, Electronics technician, TV mechanic, Telephone installer, Police - Not all but some grades, Radio - Telegraphy Colour blindness in these sectors can be hazardous due to error in colour judgement - Air traffic controller, Car body resprayer or retoucher, Cartographer, Buyers of textiles, yarns, tobacco, timber, food items like fruit, Cocoa, Chemist and chemicals (Food chemist, Laboratory analyst, Teacher of Chemistry, Chemicals manufacturer), Polishes and oils, Ceramics - Painter, Decorator of pottery, Inspector (Quality control), Safety officer, Tanner, Tobacco grader, Colour printer, Etcher, Retoucher, Colour Photographer, Colour TV technician, Manufacturing unit of coloured pencils, chalks, paints, Paint maker and distributer, Restorer of paintings/work of art, Cotton graders, Coroner, Forensic scientist, Market grader e.g fruit, vegetable, Meat inspector, Oil

 refining, Paper making, Pharmacist, Plastics.

What initiative is needed to correct these problems? Luminance clue is a beneficial way for the colour blindness. By enhancing the brightness difference between the colours is perceived. Colour defect is more noted in matt surfaces and soiled components, the use of glossy finish would overcome this problem. Bright colour and good illumination levels greatly assist the colour defect. Resistance colour confusion made by deuteranopes Resistance colour confusion made by deuteranomalous Colours completely missed on (Blue+Red)+(Violet+Brown) (Violet+Orange)+(Violet+Green) So, if you are colour blind and have not chosen Engineering as your carrier then it is advisable to choose other carrier options. All the boys who have discovered their colour blindness early are advised to avoid colour oriented careers. But still if you are determined and inspite of your being colour blind you want to choose Engineering as your career you need to go for colour blindness treatment. History of colour vision testing- In 1897 first test for defective colour vision was done with the help of coloured wools. In 1912 Colour Vision testing was started in Armed Force services. In 1959 a standard was fixed for evaluating the Colour vision.

Persons who must pass colour vision test and have perfect vision? Tests done for colour vision – Ishihara test Lantem test What is Farnsworth Lantern (FALANT) Test and what is done in this test? Instructions – You will see 3 lights – Red, Green and White / Yellow. 9 pair of colours will be seen for 2 seconds each. 2 lights are seen at a time in any combination. Patient has to call the colours – top, bottom. Interpretation - 9 pair of colour if said correctly – Pass If you fail - Suspected Red-Green Color Blindness | Colblindor Contact Red-Green Color Blindness You could already learn a lot about the different types of color blindness and what color blindness actually is . In this chapter of Color Blind Essentials I would like to tell and show you some more and deeper details about the most common and also most well known type of color vision deficiency: red-green color blindness. Discovery of red-green color blindness Memoirs of the life and scientific researches of John Dalton Already John Dalton wrote about his color vision deficiency. Red, orange, yellow, and green all appeared to be the same color to him.

The rest of the color spectrum seemed to be blue, gradually changing to purple. Dalton concluded already in the year 1798, that he can not see long wavelength red light—known as protanopia today. Some recent genetic analysis of Dalton’s preserved eyes showed, that he was suffering from deuteranopia —another form of red-green color blindness. But anyway this is the first description of the red-green color vision deficiency. In 1837 August Seebeck carried out some systematic color vision tests and found two different classes of red-green color blindness with differences in severity from weak to strong in both classes. After that investigations started to gather more details and scientists learned a lot more about our color vision: The genetic source of color vision, its deficiencies and the precise knowledge about the mechanism of color vision in our eyes.

The facts With the knowledge of the last two chapters on what color blindness really is and the different types of color blindness, we can put together the following list of facts about red-green color blindness: Facts on Red-Green Color Blindness Red-green color blindness is a generic term for protanopia (red-blindness), protanomaly (red-weakness), deuteranopia (green-blindness), and deuteranomaly (green-weakness). More than 99% of all color blind people are suffering from a red-green color vision deficiency. About 8% of all men and 0.5% of all women are suffering from it. Any severity starting from slightly over moderately, strongly or absolutely is possible. Red-green color blindness is a recessive, sex linked trait (encoded on the X chromosome). This results in much more men to suffer from it than women. It is usually inherited from a grandfather to his grandson, with the mother in between acting as the carrier of the disease. Not only red and green can’t be distinguished, but the whole color spectrum is affected by color blindness. Unfortunately many people don’t even know one of those seven basic facts on red-green color blindness.

This often causes a lot of confusion and many misunderstandings related to this term. Often confused colors The following little story happened to me a few years back. I am suffering from a strong red-blindness, so this is really a true story: I was standing on a balcony with a few friends on the fourth floor, looking into the grass fields down below us. After a while one of my friends asked, why the fire hydrant is standing in the middle of the field with no path close to it. I looked down and asked: “Which fire hydrant?” — Silence — Laughter. “Can’t you see that orange fire hydrant in the middle of the field? It stands out so obviously with its orange color!” I couldn’t see it. Only after a while, scanning the field for a fire hydrant, I found it. But not because of its color but of its structure. This story is very typical as orange and green are some of the big problem colors for red-green color blind people. But not only those colors are mixed up. Colors from the whole color spectrum can cause problems in terms of not being able to distinguish them if you are color blind. The table on the left shows five example color pairs of confusion.

As severity and type of color blindness can be very different, such color pairs are quite individual. I have chosen some colors in the color spectrum which I—as a strongly red-blind guy—can not distinguish. As you can see, not only the base colors red and green cause problems. It is the mixture of the red part in the colors which makes colors indistinguishable for my eyes. Remark: Moving in front of the computer screen or flipping the display fore- and backward can change the color perception a lot. Also if you print them out colors are perceived quite differently, specially from colorblind people. On the other side not all reds and greens are indistinguishable colors for a red-green color blind person . Some greens and some reds can be seen and named even with a strong color vision deficiency. Difference between red- and green-blindness You know by now that red-green color blindness is actually just a generic term for any form of protan (red-blind) and deutan (green-blind) color vision deficiency. But what is the difference between those two or why are they often put together into the same pot?

Let us first have a look at the things those two different main types of color blindness have in common: The main axis of colors of confusion is the same and so both types have the same main problem colors: red, orange, yellow, green, brown. The genetic information is located at almost the same place on the X chromosome. Trichromatic vision developed much later in evolution while splitting the previous information of a single channel on red-yellow-green into those two different cone encodings. The peak of sensitivity for red and green cone types is very close to each other. Trichromatic anomalies result in the shift of one of those peaks towards the other one. On the other hand there are also some differences which makes it possible to split red- and green-blind people into two separate groups while testing for color blindness: Red-blind people perceive the color red much darker. If you compare the results of Rayleigh matches—a color blindness test where you have to match yellow with a mixture of green and red—red-blind people use a much darker yellow to get a match. The colors of confusion in the blue-purple area of the color spectrum are quite different. Red-blind people will mix in much more red and still can get a match between blue and purple.

But if you compare those two types with blue-yellow color blindness the differences in between them are very small. Therefore you will most often just talk either about red-green or blue-yellow color vision deficiency and forget about the rest. By the way, if you think about the term itself and combine it with all the facts gathered together by now, you should know that red-green color blindness actually doesn’t really exist at all ;-). In the next part of Color Blind Essentials you will learn more about the different possibilities to test your color vision and how good these tests really are. Search for: Subscribe to News by Email: FREE Color Blind Check New kind of color blindness test! Try Color Blind Check and test type and severity of your color vision deficiency. Easy and fun! Genetic Mode Of Inheritance Of Colour Blindness Biology Essay Genetic Mode Of Inheritance Of Colour Blindness Biology Essay Published: Last Edited: 23rd March, 2015 This essay has been submitted by a student. This is not an example of the work written by our professional essay writers. Colour blindness is the inability of a person to differentiate between some colours.

Mostly it is genetic in nature, but can also occur due to nerve, eye or brain damage or due to exposure to any chemical. First of all paper on colour blindness were published by john Dalton who himself was colour blind. That's why this disease is also known as daltonism. The human retina consists of two types of cell which are known as: rod cells and cone cells. Rod cells are rode like in shape and active in low light while shape of cone cells is conical and are active in daylight. There are three kinds of cone cells, which consist of different type of pigments that get activated on absorption of light. These three kinds of cone cells are: Anomaloscope is the instrument through which we can easily observe deuteranomaly and protanomaly. It mixes red and green light in variable proportions, for evaluation of a fixed spectral yellow. If this is done in front of a large population of men as the amount of red is increased from a low value, first a small percentage of people will proclaim a match, while most of the addressees see the mixed light as greenish. These are the deuteranomalous observers. Next, as more red is added the majority will say that a match has been achieved.

Finally, as yet more red is added, the remaining, protanomalous, observers will declare a match at a point where everyone else is seeing the mixed light as definitely reddish. Protanomaly: in this case person is having a mutated form of long wavelength pigment, whose peak sensitivity is at shorter wavelength than in normal retina, protanomalous individuals are less sensitive to red light than normal. They are less able to differentiate between colours and they do not see mixed lights as having same colours as normal observer. They also suffer from a darkening of the red end of the spectrum. This causes reds to reduce in intensity to the point where they can be mistaken for black. . Both protanomaly and deuteranomaly are carried on the X chromosome. DEUTRANOMALY: in this person is having mutated form of medium wavelength pigment. The medium wavelength pigment is shifted toward the red end of spectrum resulting in decrease in sensitivity to green area of spectrum. This is most common form of colour blindness. The deuteranomalous person is considered "green weak". For example, in the evening, dark green cars appear to be black to Deuteranomalous people.

deuteranomates are poor at discriminating small differences in the red, orange, yellow, green region of the spectrum. TRITANOMALY: The persons suffering from this are having a mutated form of short wavelength pigment. The short wavelength pigment is shifted toward green area of spectrum. This is rarest form of anomalous trichromacy colour blindness. This mutation for colour blindness is carried on chromosome 7. Therefore it is equally prevalent in both male and female populations. OCCURANCE OF COLOUR BLINDNESS Colour blindness affects a significant number of populations, although exact proportion varies among groups. In Australia for example it occurs in about 8 % males and 0.4% females. In United States about 7% male's population is affected whereas only 0.4% female population is affected. It has been found that more than 95 percent of all variations in human colour vision involve the red and green receptors in male eyes. It is very rare for males or females to be "blind" to the blue end of the spectrum.

Prevalence of color blindness Tritanomaly (blue deficient: S-cone defect) 0.01% - DIAGNOSIS Normally colour blindness is diagnosed through Ishihara colour test, it consists of a series of pictures of coloured spots, and the test is most often used to diagnose red-green colour deficiency. A figure is embedded in the picture as a number of spots in a slightly different colour, and can be seen with normal colour vision, but not with particular colour defect. The full set of tests has a variety of figure colour combinations, and enable diagnosis of which particular visual defect is present. The anomaloscope is also used in diagnosing anomalous trichromacy. Because the Ishihara colour test consist of only numerals, it may not be useful in diagnosing young children, who have not yet learned to use numerals. In the interest of identifying this inconvenience early on in life, alternative colour vision tests were developed using only symbols (square, circle, and car). Example of an Ishihara colour test plate The numeral "74" should be clearly visible to viewers with normal colour vision.

Viewers withÂ dichromacyÂ or anomalousÂ trichromacyÂ may read it as "21", and viewers withÂ achromatopsiaÂ may not see numbers. TREATMENT There is generally no treatment to heal colour deficiencies. However certain types of coloured filters and contact lenses may help an individual to better distinguish different colours. Optometrists can supply a singular red-tint contact lens to wear on the non-dominant eye. This may enable the wearer to pass some colour blindness tests, but they have little practical use. The effect of wearing such a device is akin to wearing red/blue 3D glasses and can take some time getting used to. Additionally, computer softwareÂ and cybernetic devices have been developed to assist those with visual colour difficulties such as anÂ eyeborg, a "cybernetic eye" that allows individuals with colour blindness to hear sounds representing colours.

In September 2009, the journalÂ NatureÂ reported that researchers at theÂ University of Washington andÂ University of FloridaÂ were able to give trichromatic vision toÂ squirrel monkeys, which normally have only dichromatic vision, usingÂ gene therapy RECENT ACHIEVEMENT RELATED TO COLOUR BLINDNESS Colour-blindness Cured by Gene Injection in Monkeys A simple injection of cells has cured monkeys of colour-blindness-giving a green light to future research into improving human vision with gene therapy, a new study says According to this study monkeys were kept under investigation and it was found that some squirrel monkeys also have a form of colour blindness which is somewhat identical to humans. It was found that eyes of these monkeys lack a pigment gene that make red and green light visible to them. EXPERIMENT In the experiment the monkeys were presented to the screen filled with grey dots. Encouraged by a tone, the monkeys were to touch any dots that had changed from gray to another colour. Touching the coloured dots earned a grape juice reward. Whenever the coloured dots were red or green, though, the colour-blind monkeys acted frustrated-sometimes even shaking the display, Neitz said.

After the initial round of touch screen tests, monkeys were injected a specially engineered virus behind the retinas of two of the colour-blind monkeys. The virus contained genes for red pigment in cone cells-cells in the eye that responds to light and colour. The virus inserted the red-pigment genes into some of the monkey's green-sensitive cone cells, causing those cells to become red sensitive. RESULT Within about 20 weeks, the two monkeys were able to point out red and green, according to the study, to be published tomorrow in the journalÂ Nature. To previously colour-blind monkeys, the change confers profound abilities, noted visual neurobiologist and colour-vision expert Bevil Conway-for example, the ability to find fruit amid green leaves.

REFRENCES: Colour-blindness Cured by Gene Injection in Monkeys By: Christine Dell'Amore National Geographic News, September 16, 2009 Colour blindness-A rural prevalence survey by Maya Natu,Laxmi Smruti, 773/1-A, Erandawana, Near Kamla Nehru Park, Pune-41 004, India Percieving Colour Blindness | You&Eye Magazine 249 Views | Like Percieving Colour Blindness Not the most serious disability, colour blindness or the inability to differentiate between various colours, is the result of a visual disorder that occurs due to the absence of specific cells Colour blindness, also known as Colour Vision Deficiency (CVD), is when an individual has trouble detecting colour or differentiating between colours under normal light settings. There is no actual blindness involved, rather it is more of a deficiency in colour vision. Amazingly, this condition is gender biased. Yes! Colour blindness is generally seen more in males than in females because the gene responsible is carried on the X chromosome which men have only one, compared to women who have two X chromosomes. Since females have two of the X chromosomes, the chances of a functional gene are higher.

What Are The Symptoms? One of the obvious symptoms of this condition is that the affected individual is likely to find it difficult to identify the different colours. However, in spite of the condition becoming increasingly common, in most cases it often goes unnoticed unless the affected individual is tested in a professional lab. In severe cases, the deficiency can affect sharpness of vision. Why Does It Occur In the eye, the retina is a lining of light sensitive tissue in the back where two types of cells that detect light are found – rods and cones. Rods detect only light and darkness and work well in low light levels. Cone cells detect the actual colour and are concentrated near the centre of one’s vision. There are three types of cones that see colour: red, green and blue. The brain uses these three colour cone cells to determine the actual colour perception. Colour blindness occurs when one or more of the colour cone cells are absent, non-functioning or detect a different colour than normal. Inherited Colour Vision Deficiency or colour blindness can also be passed on genetically. If colour vision problems surface later in life, they are a result of disease, trauma from injury, toxic effect from drugs, metabolic disease or vascular disease.

In such cases, the condition is also known as acquired colour blindness. Disease-specific colour blindness often affects both eyes differently, and the defect usually worsens over time. Diagnosing Colour Blindness Detecting congenital colour blindness can be difficult in young children particularly as they may be unaware of the symptoms that they are experiencing. The best option is to teach children to identify colours starting at a young age. Additionally, eye checkups with an optometrist will normally consist of colour vision tests on routine basis, so the deficiency can be detected easily. Other times, individuals may have to request specifically for the colour vision test. Also, if there is any discomfort detected in vision, a general practitioner can also examine for the symptoms of colour deficiency. When it comes to detection methods, there are various options. Being Colour Blind A colour blind person, even though not blind completely, can find difficulties in day-to-day life as against a person having a normal vision. Simple activities like choosing and preparing food, gardening, driving a car, shopping, etc. get affected due to the inability to differentiate between colours. Treatments Currently, there are no treatments for congenital colour blindness and usually it does not cause any significant disability.

Special contact lenses and glasses are also available that are known to help people with colour blindness to differentiate between similar colours. Types Of Colour Blindness A normal vision will have all the three types of light cones functioning well, known as trichromacy. In colour blindness, the degrees of vision deficiency can be summed up in three types and further in depth dimensions of each: Anomalous trichromacy is a common type where the individual will be colour blind just to some extent and this occurs when one of the three cone pigments is altered in its spectral sensitivity. Dichromacy is when only two types of the cones are able to perceive colour, that means there is total absence in the functioning of one cone type. Monochromacy is where an individual cannot see any colour at all, thus their vision consists only of different shades of grey like watching on an old black and white television set. This article has been written with inputs from Dr Naseem Fakhereddeen (Specialist Ophthalmic Surgeon, iCare Clinics) Colour Blindness :: Eye Health Central Colour Blindness Colour Blindness Contrary to its name, colour blindness does not refer to actual blindness.

Rather it is a condition in which the ability to properly see colours, or differentiate between them, is either diminished or completely lacking. In rare cases it can be caused by injury or specific drugs, but in most cases its origins are purely genetic, and affects the development of one or more sets of retinal cones that perceive colour in light. Colour blindness affects males much more than females, and is found in 8% and 1% of each, respectively. While it is typically considered to be a mild disability, there are some circumstances where some types of colour blindness can be advantageous. Due to the way that colours are processed differently, certain types of camouflages, which are intended to blend in with their surroundings, may appear to stand out. Some colour blind people can differentiate between two similar colours that most people perceive as two samples of the same colour. Types of Colour Blindness In some rare situations, colour blindness can be caused by an injury to the eye, optic nerve, or brain, affecting its ability to process colours properly. Some diseases, drugs, or chemicals can also trigger the condition, but are incredibly uncommon. A vast majority of colour blind people can attribute their condition to genetics.

Depending on how the development of their eyes and brains were effected, the details and parameters of their colour blindness may be different. In fact, there are quite a few different variations of colour blindness, with details on them listed below. Monochromacy – Often referred to as “total colour blindness", monochromacy is inability to distinguish colours at all. Anyone with this type of colour blindness views the world in black and white, like old television and movies. It is caused when two or all three of the cone pigments within the eye are missing or defective, and colour and lightness vision is reduced to a single dimension. Under monochromacy, there are two sub types. Rod Monochromacy – Also called achromatopsia, this form is an exceptionally rare disorder. Those that have this form of colour blindness are totally unable to distinguish any colours as a result of either absent or non-functioning retinal cones. Issues commonly associated with this form are light sensitivity, involuntary eye oscillations, and poor vision. Cone Monochromacy - A rare total colour blindness that usually doesn't affect visual acuity at all, unlike rod monochromacy.

This form, however, can be the result of having multiple forms of dichromatic colour blindness simultaneously. For instance, someone with both protanopia and tritanopia can be considered to have cone monochromacy. Dichromacy - A relatively severe form of colour blindness in which one of the three basic colour mechanisms is either absent or non-functional. Because it is hereditary in nature, and effects the X chromosome, is it found predominantly in males. There are three sub categories of dichromacy, protanopia, deuteranopia, and tritanopia, each occurring when one of the cone pigments is missing and colour is reduced to two dimensions. Protanopia - In reference to the three primary colours, and stemming from the Greek “prot”, meaning “first”, this form of dichromacy is caused by the complete absence of red retinal photoreceptors. People with this form of colour blindness have difficulty distinguishing between blues and greens, as well as between reds and greens. Completely pure red cannot be seen at all, and appears black. Purples and blues cannot be distinguished from one another, and orange-reds appear like very pale or dim yellows.

It is hereditary, and present in 1% of males only. Deuteranopia - “Dueter”, Greek for “second”, refers to the next primary colour, green. This form of colour blindness is caused by the absence of the green photoreceptors within the eye. It affects differentiating between colours much in the same way as protanopia, but without the dimming effect. Like protanopia, it is only found in about 1% of the male population, not in females. Tritanopia - “Trit”, Greek for “third”, refers to blue, and the complete lack of colour receptors responsible for detecting it. This form of colour blindness is very rare, and involved the presence of only two cone pigments, red and green. For people with this form, blues appear greenish, yellows and oranges appear pinkish, and purple colours appear deep red. It is hereditary, but unlike protanopia and deuteranopia, tritanopia is not sex-linked, meaning it appears in both males and females.

Anomalous Trichromacy – A more common type of colour blindness, it is hereditary in nature, and involved one of the three cone pigments being less sensitive, rather than completely absent or damaged. The symptoms are very similar to their dichromatic counterparts, only less severe. Protanomaly - A mild form of colour blindness in which the sensitivity of red retinal receptors is diminished, but not absent. The result is poor discrimination between reds and greens. It is hereditary, sex-linked, and present in 1% of males. Deuteranomaly, - By far the most common type of colour vision deficiency, this form of colour blindness mildly affects discrimination of reds and greens. It is found in approximately 5% of European males, but not females. Tritanomaly - A very rare form of colour blindness that mildly affects discrimination of blues and greens, as well as yellows and reds. Like all the other forms, it is hereditary, but can be found in both males and females alike. What Causes Colour Blindness? In a vast majority of instances of colour blindness, the cause is genetic, with the condition being passed down from parent to child.

In fact, there are many know gene mutations that are capable of causing colour blindness, at least 19 different chromosomes and 56 individual genes. Because of the nature of these anomalies, which are typically linked to the X chromosome, they affect men far more than women. If a mutated X chromosome is inherited by a woman, a second, normal X chromosome can override it, resulting in normal vision. Men, however, only have one X chromosome, and will be affected should they inherit a mutated gene. Hereditary forms of colour blindness can be present at birth, or may develop sometime during childhood, adolescence, or even adulthood. Different genetic mutations have different ways of affecting vision, not just in terms of colour identification, but in the progression of the condition. Some forms will stay consistent throughout life, while others may worsen over time. In far fewer instances, colour blindness can be caused by injury, or another form of trauma. Brain or retinal damage can certainly affect vision, as well as any type of injury that causes swelling of the brain in the occipital lobe. Prolonged exposure to UV light can also lead to colour blindness.

Not all of these injuries will result in colour blindness immediately, as the damage may not present itself until later on in life. It can even be caused by a serious deficiency in vitamin A. How Is Colour Blindness Diagnosed? The post popular test to detect red-green colour blindness is the Ishihara colour test, which consists of a series of images comprised of coloured spots. A figure, such as a letter or number, is hidden in the image, composed of one colour of spots, while being completely surrounded with an alternate colour. With normal visual abilities, the image will appear to stand out, and can be identified easily. However, with a condition of colour blindness, the image may not be perceived at all. Different colours and contrasts are used to isolate different forms of colour blindness. One of the disadvantages of this test is that it relies on the subject’s ability to identify numbers or letters, which means it isn't useful for use with small children who have not yet learned those symbols. Other variations of this test exist, as well. Several branches of the United States military use the Farnsworth Lantern test, which allows anyone with mild colour blindness, approximately 30% of all colour blind people who attempt, to pass.

The Farnsworth-Munsell 100 hue test involves arranging a set of coloured object in order, which is based on a transitional colour gradient. Two distinct colours are placed at either end, and the subject is left to arrange the other items in an ordered fashion between them. Those with difficulty distinguishing between some colours will unlikely be able to complete the test accurately. How Is Colour Blindness Treated? Unfortunately, there is currently no cure for colour blindness. There are lenses available, both contact and eyeglass, that will help differentiate between colours that might otherwise appear very similar or even identical, but they can not help the viewer perceive the true and accurate colour. In some cases, the coloured lenses might make it easier to distinguish between some colours, but harder for others. Modern technology is providing some solutions, however. Often referred to as “colour blind mode” computers, tablets, and cell phones can adjust the colours they display to those more easily recognized by the user. While the image on the screen may not be an accurate representation of the original work, it can be tailored to individual types of colour blindness, making the device more usable and less confusing. Research is currently being performed on squirrel monkeys, which naturally only have dichromatic vision.

By using gene therapy, they have been able to alter the monkey's eyes, enabling trichromatic vision, like humans. There is still much more research and testing needed, but this shows promise for possible future treatments of colour blindness in humans. More Eye Disorders Articles Color Blindness - National Library of Medicine - PubMed Health About the Cone Cells About Color Blindness Most of us share a common color vision sensory experience. Some people, however, have a color vision deficiency, which means their perception of colors is different from what most of us see. The most severe forms of these deficiencies are referred to as color blindness. People with color blindness aren't aware of differences among colors that are obvious to the rest of us. People who don't have the more severe types of color blindness may not even be aware of their condition unless they're tested in a clinic or laboratory. Inherited color blindness is caused by abnormal photopigments. These color-detecting molecules are located in cone-shaped cells within the retina , called cone cells . In humans, several genes are needed for the body to make photopigments, and defects in these genes can lead to color blindness.

There are three main kinds of color blindness, based on photopigment defects in the three different kinds of cones that respond to blue, green, and red light. Red-green color blindness is the most common, followed by blue-green color blindness. A complete absence of color vision —total color blindness — is rare. Sometimes color blindness can be caused by physical or chemical damage to the eye, the optic nerve, or parts of the brain that process color information. Color vision can also decline with age, most often because of cataract - a clouding and yellowing of the eye's lens. NIH - National Eye Institute What works? Research summarized Color Blindness – Information : Identification : Solutions :: Everything you need to know about Colour Blindness Color Blindness What is Color Blindness Color blindness is the inability to differentiate certain colors. It comes in various flavours with the most common being red green color blindness. There are multiple causes, but color blindness is primarily inherited by way of a mutated X Chromosome. Due to the fact that men only have one X chromosome, if they are handed a faulty X chromosome (by a carrier mother) they will be color blind.

Women on the other hand have two X chromosomes, which is why many less women are color blind than men. The odds that both X chromosomes are faulty is extremely low, and the healthy one will take precedence providing normal perception of color. Being color blind is officially considered a disability, however there have been studies documenting certain advantages including penetrating some camouflages. For instance – it was found during World War II that analysis of aerial photos yielded better results if at least one member of the surveillance team was color blind. It has also been suggested that females with one mutated X chromosome may be afforded an extra dimension of color awareness as they may have at least four types of cones in their eyes rather than two. What Causes Color Blindness Color Blindness is most commonly the result of hereditary reception of a genetically defective X chromosome. The chromosome usually comes from a carrier mother, and has a 50% chance of being passed to her son. A daughter of the same mother will have a 50% chance of also becoming a carrier, and is only likely at risk of becoming color blind if the father is color blind. Color blindness can also be caused by accidents and other head trauma where permanent damage to the eyes occurs.

This can happen as a baby (Shaken Baby Syndrome), or also later in life. UV Rays also present a risk of becoming color blind; they are in fact the leading cause of normal eye blindness in the world. The 3rd way to get color blindness is through other hereditary diseases such as Diabetes. The list of diseases is long, and you can see the full list on the ‘Causes’ Page in the menu to the left. It should be noted that the amount of documented cases on these illnesses causing color blindness is limited, and as such the validity of these claims may be questionable. Common Types of Color Blindness Color blindness comes in the following types: Red Green Color Blind(most common) Dichromacy (protanopia and deuteranopia) Anomalous trichromacy (protanomaly and deuteranomaly) Blue Yellow Color Blind Anomalous trichromacy (tritanomaly) Total Color Blindness (least common) You can read the How it Works (science) page to understand what each of the scientific terms above means. Fortunately, green deficiency, which is arguably the mildest type is also the most common type of color blindness. However second most common is the total inability to see red.

To really understand what this means to someone to live with this condition compare the following two images. You might feel sorry for anyone you know with this condition – given the amount of color they don’t get to see, but remember that they were born this way and don’t know the world to look any different. The most common type of color blindness is red green color blindness, this type affects about 95% of all color blind people. The remaining 5% is made up of blue yellow color blindness, and less commonly – total color blindness. Within each color deficiency is the possibility of being either partially blind to that color, or totally. For example green deficient is more common, but being totally unable to see red is second most common. Testing for Color blindness The most common way to test for color blindness is known as the Ishihara Color Test. Dr Shinobu Ishihara, a University of Tokyo professor, created a series of plates to be used to identify red green color blindness. As you see in the image below, they contain a series of 38 plates; however an issue is normally well apparent after only a few. Testing all 38 plates will help to determine the level of severity of the sufferer.

We have prepared a color blindness test using these Ishihara test plates which you can access at any time via the left hand menu if you think that you, or someone you know, might be color blind – or just for fun! Living with Color Blindness Living with color blindness can be anything from trivial to frustrating, and sometimes even dangerous. Some people go their entire lives not knowing they were actually mildly color blind, whereas some are reminded daily of the inconveniences and risks of their disability. Reminders come in the form of not knowing whether you’re looking at a stop or go traffic light, not knowing if your steak is cooked, or whether or not the tomato you wanted to use is ripe or not. But for some perhaps the biggest frustration is not being able to pursue the career you always dreamt of. Many arts based careers such as design can be nearly impossible for those with color blindness, while some such as being an air force pilot simply aren’t allowed. Share this:

Question: The inability or near inability in colour blindness to differentiate between some colours is, in the most common form of it, between red and which other colour?
Answer: Green