Colour blindness

What is colour blindness? 

Colour blindness, or colour vision deficiency, is typically an inherited condition, meaning you're born with it. It's caused by a fault in the development of the cone cells in the retina. While most cases are genetic, it's also possible to develop colour blindness later in life due to other conditions like diabetes, glaucoma, or as a side effect of some medications. 
 
People with the most common types of colour blindness, like red‑green colour blindness, find it hard to tell the difference between reds, greens, browns, and oranges. They might also confuse blues and purples. A less common form is blue‑yellow colour blindness, which makes it difficult to distinguish between blue and green, or yellow and red. It's a misconception that colour blind people only confuse red and green. The condition can affect the perception of many different colours. 

What the experts say about colour blindness

Our expert optometrists frequently conduct tests for colour blindness. In this video, one of our optometrists explains what is colour blindness, the different types of colour blindness, and how a colour blind test works. 

What causes colour blindness? 

So, what causes colour blindness? In the vast majority of cases, it is related to genetics.

Inherited condition 

Most people with colour blindness are born with it. It's a common inherited condition passed down from parents to their children on the X chromosome. This is why red‑green colour blindness is much more common in men. 

A man only needs to inherit the gene from his mother, whereas a woman needs to inherit it from both her father and mother to be colour vision deficient.

Acquired colour blindness 

You can develop colour blindness later in life, often due to an underlying health condition like glaucoma, diabetic retinopathy, or multiple sclerosis. It can also be caused by certain medications, ageing, or an injury to the eye. 
 
If you’ve noticed any changes in how you see colours, it’s a good idea to book an eye test. Your optometrist can check for any signs of underlying problems and help you understand what’s going on.

How is colour blindness diagnosed?

An optometrist can diagnose colour blindness during a comprehensive eye examination. If you or your child have trouble naming colours, it’s a good idea to get it checked. Diagnosing it early is important, as it can affect learning and career choices. 
 
An optometrist will use specially designed charts to assess your colour vision. These tests are quick, painless, and can accurately determine the type and severity of colour blindness. 

Ishihara test

This is the most common test for colour vision. It involves a series of plates, each made up of dots of different colours and sizes. Within the pattern are dots that form a number or shape, which someone with normal colour vision can see, but someone with vision deficiency may not be able to see or may see something different.

Slit‑lamp examination

While not a direct test for colour blindness, the optometrist will examine the overall health of your eyes to rule out other conditions that could be causing changes in your vision, such as glaucoma or diabetic retinopathy. 

When colour blindness needs medical help 

Inherited colour blindness is a stable condition and doesn't get worse over time. However, you should see an optometrist or your GP if you notice a sudden change in your colour perception. This could be a sign of an underlying health issue that needs attention, such as problems with your retina causing blurry vision or cloudy vision.