Kevin Huang, BSc Pharm Student
“A world without colour…” For most people, this would be a strange world to live in. After all, we use colour in most aspects of our everyday lives. Whether it’s driving, cooking, or creating art, colour differentiation is essential to help us complete our work. But did you know there are people with colour blindness (also known as colour vision deficiency) who are thriving around the world? Although this condition may impair your ability to distinguish colours, early education and training will help children adapt. Today, we’ll spend some time exploring this condition to help you gain insight into life with colour vision deficiency.
What is Colour Vision Deficiency?
Colour vision deficiency is an ocular disorder that impairs our ability to differentiate specific types of colour. In our eyes, we have two different types of photoreceptors which contribute to vision. Rods are photoreceptors which help us see in low light environments. Recall the last time you laid awake in your bed late at night. The whole room seemed to exist in shades of white, black, and grey. This is the work of rods, creating a visual of your surroundings with the dim light.
On the other hand, cones are photoreceptors that create the coloured vision we use in our daily life. Cones are divided into three groups; each are responsible for receiving light input corresponding to different primary colours. These include the red, blue and green wavelengths of light. A mixture of these three different colours of light helps us perceive vision in the full colour spectrum. If one class of cone is absent or non-functional, it may affect the individual’s ability to see colour the way most people do. This is important since colour vision deficiency may affect one’s ability to successfully complete their day-to-day tasks.
There are numerous classes of colour vision deficiency. Different diagnoses depend on which photoreceptors of the eye are affected.
- Red (Protanomalous) – Green (Deuteranomalous) Colour Vision Deficiency: The most common colour blindness in which the red or green cones are absent or non-functional. These individuals can identify two of the primary colours, but fail to perceive the third, thus affecting the shades of colour they see in life.
- Blue-Yellow (Tritanomalous) Colour Vision Deficiency: A more rare condition, blue-yellow colour vision deficiency affects the blue and green cones. This prevents individuals from identifying shades of blue and yellow (a mixture of blue and green light).
- Total (Achromatopsia) Colour Vision Deficiency: The rarest form of colour blindness. Individuals with this condition can’t see colour at all, however, can determine shades of colour (dark vs light).
Diagnosis of the Condition
When you’re visiting your ophthalmologist, you might have noticed the number plate tests. The Ishihara Plates are colour-dotted plates designed to diagnosis patients with colour vision deficiency. The plate will have two shades of colour, one which will form a number and the other will form the background. Most individuals can readily identify the number on the plate. Patients with colour blindness may struggle with these tests, and this provides the ophthalmologist with a hint to pursue further investigations.
Another test an ophthalmologist may perform is the arrangement test. Participants are asked to separate the coloured objects into similarly shaded groups. Individuals who struggle with this assessment are likely to be affected by colour vision deficiency.
Although there are currently no cures for colour blindness, most patients don’t require medical treatment. Individuals with this condition are likely to adapt to their environments and developed systems to overcome these challenges. This is why it’s vital for children with colour vision deficiencies to be identified early in their lives, so they can be taught to work around this condition.
Sometimes, people with normal vision may acquire colour vision deficiency. This may be due to age, ocular disorders (e.g. cataracts, glaucoma, or macular degeneration), ocular damage, and/or medications. In these cases, patients may consult with their ophthalmologist to determine whether visual aids can help correct their vision (e.g. coloured contact lens, anti-glare glasses).
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- Colour Blindness [Internet]. HealthLink BC. 2017 [cited 3 January 2019]. Available from: https://www.healthlinkbc.ca/health topics/hw143997
- Colour Deficiency [Internet]. The Canadian Association of Optometrists. [cited 3 January 2019]. Available from: https://opto.ca/health-library/colour-deficiency
- Color Vision Defects [Internet]. ClinicalKey. 2013 [cited 3 January 2019]. Available from: https://www-clinicalkey-com.login.ezproxy.library.ualberta.ca/#!/content/book/3-s2.0-B9780123838346001427?scrollTo=%23hl0000208