Focus on Colour Vision Deficiency (CVD)


Please note that this page is for information only, it is not a replacement for medical advice.
If you have any questions regarding Colour Vision Deficiency (aka Colour Blindness) or any other eye condition,
please consult a medical professional. 

What is Colour Vision Deficiency?

Colour Vision Deficiency (CVD) - often referred to as 'colour blindness' - is a condition that affects a person's ability to distinguish between different colours. People with CVD may see colours differently than those with normal colour vision or may not be able to distinguish certain colours at all.

Colour Vision Deficiency is typically an inherited condition that is caused by a genetic defect in the cones, which are the specialized cells in the eye that are responsible for detecting colour. There are three types of cones in the eye that detect different colours, made of different wavelengths of light:

  • Red cone cells detect long wavelengths of light
  • Green cone cells detect medium wavelengths of light
  • Blue cone cells detect short wavelengths of light

When one or more of these cones is not functioning properly, a person may experience CVD.

The most common form of Colour Vision Deficiency is red-green colour blindness, which affects about 8% of men and 0.5% of women of Northern European descent. This type of CVD can range from mild to severe and can make it difficult to distinguish between reds, greens, and yellows.

While there is no cure for colour vision deficiency, most people with the condition are able to live normal, healthy lives by using certain strategies and tools to help them compensate for their colour vision deficiency.


"CVD is most commonly genetic or inherited.
Inherited CVD does not improve or get worse with age.
Most forms of inherited CVD do not affect the eye’s ability to see fine detail.




Different types of Colour Vision Deficiency (CVD) 

Red-Green Colour Blindness

The most common form of colour vision deficiency is known as red-green colour blindness, affecting approximately 1 in 12 men and 1 in 200 women. Individuals with this type of Colour Vision Deficiency often struggle to differentiate between red, yellow, and green. Additionally, they may mistake red for black or encounter difficulty distinguishing various shades of purple from blue.

Categorizing CVD by Cones

Colour Vision Deficiency can also be categorized based on which types of cones in the eye are damaged or missing. When the cones responsible for detecting red light are absent or malfunctioning, it is termed ‘protanopia’ or ‘protan colour blindness’.

In cases where the cones for detecting green light are missing or dysfunctional, it is referred to as ‘deuteranopia’ or ‘deutan colour blindness’.

Both protanopia and deuteranopia lead to red-green colour blindness, as the inability to perceive red or green makes distinguishing between the two colours challenging.

Tritanopia: Blue-Yellow Colour Blindness

In situations where the cones for detecting blue light are missing or not functioning properly, the condition is called ‘tritanopia’. Individuals with tritanopia have difficulty perceiving blue, resulting in blue-yellow colour blindness.

Although it is occasionally mistakenly described as blue-green colour blindness, this condition is less common. It affects less than 1% of both men and women. People with tritanopia may struggle to differentiate between blue and green, as well as between yellow and red. Blues may appear as green or even black, yellow may seem white, orange may appear pink, and purple can be mistaken for red.

Achromatopsia or Monochromacy: Total Colour Blindness

In extremely rare cases where two or all three types of cones are missing or damaged, individuals experience total colour blindness, known as achromatopsia or monochromacy. Those with total colour blindness are unable to distinguish any colours and perceive everything in shades of grey.


How someone with Colour Vision Deficiency (CVD) also known as Colour Blindness might view the world  

View of a field of sunflowers, on a summer's day.  Theree is a large sunflower close-up at the front. the image is grey and pale pink, rather than the bright yellows, greens and blues that you might expect. This is to simulate how someone with total colour blindness might experience the view      

Please note this is a simulation of Achromatopsia or Monochromacy (Total Colour Blindness), based on the anecdotal experiences of people who have the condition. This image is not the experience of everyone with Colour Vision Deficiency (CVD) and is for illustration purposes only.


Symptoms of Colour Vision Deficiency 

The most common symptom of Colour Vision Deficiency is difficulty distinguishing between certain colours or shades of colours. This can range from mild difficulty distinguishing between certain shades of red and green to a complete inability to see any colours at all.

Other symptoms of CVD may include:

  • Difficulty reading colour-coded information, such as charts, maps, and graphs.
  • Difficulty distinguishing between similar colours, such as blue and purple or red and brown.
  • Problems with colour-related tasks, such as sorting laundry or picking out matching clothing.
  • Seeing colours as washed-out or dull, or perceiving colours differently than others.

It's important to note that not all people with colour vision deficiency experience the same symptoms, and the severity of the condition can vary widely from person to person.

Additionally, some people with mild colour vision deficiency may not even realize that they have the condition until they undergo colour vision testing. If you suspect that you or a loved one may have CVD, it's important to see an optometrist for a comprehensive eye exam and colour vision testing.

"Worldwide 8% of men and 0.5% of women have a red/green type of colour vision deficiency."

Colour Blind Awareness


Diagnosis of Colour Vision Deficiency

Colour vison deficiency is typically diagnosed through a series of tests that assess a person's ability to distinguish between different colours. The most commonly used tests for colour vision deficiency are the Ishihara Colour Test and the Farnsworth-Munsell 100 Hue Test.

The Ishihara Colour Test involves a series of plates with coloured dots or shapes that are arranged in a specific pattern. Each plate has a number or symbol hidden within the pattern, which is visible only to people with normal colour vision. People with colour vision deficiency may not be able to see the number or symbol and will see a different pattern instead.

The Farnsworth-Munsell 100 Hue Test is a more detailed test that requires a person to arrange a set of coloured tiles in order of hue, from red to purple. This test can help identify the specific type and severity of colour vision deficiency.

In addition to these tests, an optometrist may also use other tools, such as a colour vision screening device, to assess a person's colour vision.

If you suspect that you or a loved one may have colour vision deficiency, it's important to see an optometrist for a comprehensive eye exam and colour vision testing.

"Disease or injury that damages the optic nerve or retina can also cause a loss of colour recognition. These include diabetes, glaucoma, AMD, Sickle Cell Anaemia, Alzheimer's Disease, Parkinsons Disease, MS and leukemia."

Treatment of Colour Vision Deficiency

Currently, there is no known cure for colour vision deficiency. However, there are some strategies and tools that can help people with colour vision deficiency compensate for their condition and improve their ability to distinguish colours.

Some of these strategies include:

Colour-coded labels

Using colour-coded labels for things like medication, clothing, and food can help people with colour vision deficiency easily identify and differentiate between different items.

Assistive Technology 

There are several apps, software programs, and devices available that can help people with CVD distinguish between colours. These include colour filters, colour identification apps, and colour correction glasses.

Assistive technology software from Dolphin includes screen magnifiers, screen readers and accessible book readers and text-to-speech software, which can help you navigate your daily life. These tools can make it easier to read, write, study and use technology, as they all have the ability to change and customise colour contrasts for backgrounds, lettering and highlights. 

Whatever your experience is with computers, Dolphin assistive technology can help. 

Education and awareness

Understanding the limitations of colour vision and learning to recognize and compensate for colour vision deficiencies can help people with colour blindness navigate their daily lives more effectively.

It's important to note that the specific strategies and tools that work best for each person with colour vision deficiency will depend on the type and severity of their condition. A comprehensive eye exam and consultation with an optometrist can help determine the best course of action for each individual.


Living with Colour Vision Deficiency

Living with colour vision deficiency can present some challenges, but with the right strategies and tools, most people with the condition are able to lead normal, healthy lives.

Here are some tips for living with CVD:

Educate yourself

Learn as much as you can about colour vision deficiency and how it affects your vision. Understanding your limitations and knowing how to compensate for your condition can help you navigate daily life more effectively.

Use colour-coded labels and markers

Use colour-coded labels and markers for things like medication, clothing, and food to help you easily identify and differentiate between different items.

Use assistive technology

There are many apps, software programs, and devices available that can help people with CVDdistinguish between colours. These include colour filters, colour identification apps, and colour correction glasses.

Seek accommodations

If you're in school or the workplace, seek accommodations that can help you navigate tasks that require colour vision, such as reading charts, maps, and graphs.

Communicate with others

Let people know that you have colour vision deficiency, and be open about your limitations. This can help others understand your perspective and avoid misunderstandings.

Embrace your unique perspective

Remember that colour vision deficiency is a part of who you are, and it can give you a unique perspective on the world. Don't be afraid to embrace this perspective and use it to your advantage.


Where to find more information about Colour Vision Deficiency (CVD)

RNIB Logo-1

Royal National Institute for Blind People 

RNIB provides information, advice and support for people with CVD, other visual impairments and sight loss conditions.  

Visit RNIB >

NHS Logo


To find out more about CVD and learn when and how to get treatment in the UK, visit the NHS website. 

Visit NHS website >

AOA logo

American Optometric Association (AOA)

The leading authority representing more than 48,000 doctors of optometry, optometric professionals and optometry students.

Visit AOA website >

Dolphin Computer Access Logo

How Dolphin assistive technology can help you live with Colour Vision Deficiency - formerly known as colour blindness

How Dolphin makes a difference

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If you are blind or partially sighted, Dolphin assistive technology helps you maintain your independence. We have developed specialist software, specifically for people experiencing sight loss.

For over 35 years, we have made a difference to the lives of millions of people who are blind or partially sighted. Dolphin software includes screen magnification and screen reading technology, book reading apps and easy-to-use computer programs. These work to help people with sight loss to work or study, to complete tasks independently at home, to access the internet and read all the information on a computer screen.

Assistive Tech for Home

About SuperNova

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SuperNova is a range of assistive technology for people who are blind or partially sighted. SuperNova provides exceptional magnification, screen reading and braille support and enables you to explore your computer screen. 

Choose the edition that suits your vision:

  • SuperNova Magnifier
  • SuperNova Magnifier & Speech
  • SuperNova Magnifier & Screen Reader
  • SuperNova Enterprise

SuperNova Information

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