Understanding Colour Vision
Colour vision is a fascinating and essential aspect of our daily experience, allowing us to perceive the world around us in vivid detail. The ability to differentiate between various hues enables us to navigate environments, communicate non-verbally, and enjoy art, nature, and even food in a more meaningful way.
What Is Colour Vision?
Colour vision refers to the ability to distinguish between different wavelengths of light that are interpreted by the brain as specific colours. This ability relies on the function of cone cells in the retina, each sensitive to a specific range of light—red, green, or blue. A healthy, functioning visual system allows us to see the broad spectrum of colours that make up our environment.


The Importance of Routine Eye Exams
Regular eye exams are essential for monitoring colour vision and overall eye health. Routine tests, like the Ishihara or Farnsworth D-15 tests, help detect any colour vision deficiencies and help with early detection of conditions that may affect colour perception, such as cataracts, macular degeneration, or retinal issues. Early diagnosis can slow progression and preserve vision.

Factors Affecting Colour Vision
Colour vision problems can be congenital (present from birth) or acquired. The most common type is colour vision deficiency, often referred to as 'colour blindness', which is a misnomer as individuals can still see colour but have difficulty distinguishing between certain colours, often red and green (there is in fact a rare form of color vision deficiency known as achromatopsia where a person's vision is completely devoid of colour, seeing the world in only in shades of black and white). This condition can be hereditary, but age, diseases, or eye injuries can also impact colour vision over time. Here are a few key factors that can impact your colour vision:
Genetics: The most common cause of colour vision deficiencies is genetic. Men are more likely to experience colour blindness, as the condition is linked to the X chromosome.
Age: As we age, the lenses of our eyes naturally yellow and lose their transparency, which can affect the perception of colour. This is a common part of the aging process and can lead to a gradual decline in colour discrimination.
Eye Diseases:Â Conditions like cataracts, glaucoma, or macular degeneration can interfere with your ability to perceive colours.
Medication Side Effects:Â Certain medications, especially those that affect the central nervous system or the eyes themselves, may interfere with colour vision.
Eye Injuries:Â Trauma to the eye or head can lead to disruptions in the function of the retina or the optic nerve, potentially resulting in a loss of colour vision.
What are the types of inherited colour vision deficiencies?
Colour deficiencies are a common genetic disorder that affects about 8% of men and 0.5% of women worldwide. This means that there are roughly 300 million people with colour deficiencies globally.Â
Red/green colour deficiencies disproportionally occur in men/people assigned male at birth due to its genetic inheritance pattern (X-linked recessive).
Genes responsible for blue/yellow inherited color vision deficiency are not located on the X-chromosome. Unlike red/green color deficiencies, this condition is inherited differently and is therefor much rarer.

Anomalous Trichromacy
In Anomalous Trichromacy, the all three cones are present however the peak sensitivity to one of the cones is shifted.
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Protanomaly - a reduced or shifted sensitivity to red light
Deuteranomaly - a reduced or shifted sensitivity to green light (the most common form)
Tritanomaly - a reduced sensitivity to blue light (the most rare)

Dichromacy
Dichromacy is the result of one type of colour receptor being absent completely, causing a total inability to see specific colors.
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Protanopia - inability to perceive colours on the red spectrum of visible light
Deuteranopia - inability to perceive colours on the green spectrum of visible light
Tritanopia - inability to perceive colours on the blue spectrum of visible light

Monochromacy
Finally, there is monochromacy, also known as achromatopsia. This is genuine colour blindness, where the cone cells are either entirely absent or non-functional. Achromatopsia is extremely rare, affecting only about 1 in every 33,000 people. Individuals with monochromacy perceive no colour in their environment, instead seeing varying shades of grey from black to white. Individuals affected may experience further vision issues, such as heightened sensitivity to light (photophobia), involuntary eye movements (nystagmus), and nearsightedness (myopia).

What can be done for colour vision deficiencies?
While there is no cure for inherited colour vision deficiencies, there are special glasses and contact lenses that may assist some individuals in distinguishing between colours more effectively. Most people with colour vision deficiencies manage everyday activities without issues.
The most commonly known glasses for colour vision deficiencies are called EnChroma whose lenses use selective filters to increase contrast between the red and green colour signals to account for the overlap and alleviate symptoms of red-green colour deficiencies. (https://enchroma.com/)

Colour vision is an essential aspect of how we interact with the world, and monitoring it is key to maintaining eye health. Whether you are experiencing a subtle shift in how you see colours or have concerns about potential vision problems, routine eye exams are the best way to ensure that your eyes remain healthy and your colour vision intact. Don’t wait for problems to become obvious—schedule regular check-ups with your optometrist to stay ahead of any changes and protect your vision for years to come.
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