Colour Blindness and Colour Blind Tests

What is colour blindness?

Colour Blindness – or more accurately Colour Vision Deficiency (CVD) – is the inability to see colours accurately.  Sufferers may have trouble distinguishing between certain colours such as Greens and Reds, especially if they are of the same brightness.  It can be diagnosed by a simple colour blind test by an optometrist.

Most cases of colour blindness are inherited, and affects boys more than girls.  1 in 12 males and 1 in 200 females suffer from some form of colour blindness.  Red-green colour blindness is the most common form, and the defective gene is called on the X chromosome; hence it is passed on from the mother.

Certain eye diseases such as optic neuritis, and particular medications such as hydroxychloroquine (Plaquenil) can cause acquired colour blindness, but these are rare.  Anyone who notices a change in their colour perception should present to an eye health professional for a comprehensive eye exam including a colour blind test.

In the back of our eyes, we have three types of colour sensors which detect Red, Green and Blue light.  When one or more of these sensors (called cone photoreceptors) are defective or missing, colour blindness occurs.

Color Blindness Symptoms

Symptoms of colour blindness depend on severity; and people with the mildest forms may be unaware they have a problem until a colour blind test is conducted.  In moderate and severe cases, colour blindness can affect everyday life.

During School

With the popularity of screen based school work, colour blind students often have trouble absorbing colour-rich information from screens.  Colour blind students may be confused by Red and Green markers being used on smartboards or whiteboards.

If your child complains about certain colours being hard to see on the board, on a screen or on the page; we recommend booking them for a colour blind test.


Many forms of colour blindness will not affect the ability to drive; however certain forms such as Protan colour vision defects can cause red signal lights to appear very dim.  Sufferers will need to be aware of such issues especially when driving in poor weather conditions or at night.

At present, there are no specific requirements for colour vision to pass the vision standards for an Australian commercial or private driving licence.

If you have trouble seeing red signal lights when driving, we recommend booking in for a colour blind test.


Certain forms of colour blindness can affect the career choices of sufferers.  Occupations such as racing, the fire service, marine engine drivers, and the defence force may set specific colour vision requirements depending on the particular role beign applied for.

At present, there are no specific requirements for colour vision to become an electrician; however severe forms of colour blindness will create obvious difficulties in that line of work.

Colour Blind Test

A simple test performed by an optometrist can determine if you have colour blindness.  The most common colour blind test is the Ishihara Pseudoisochromatic Plate Test.

This test involves showing you a number of circles made up of a colour background of irregularly sized dots, and a number that appears in a different set of colours.  Those with normal colour vision will be able to see all the different numbers, while those with a Red-Green colour vision defect will struggle to see the numbers.  For younger children who are not confident with their numbers, there are also special plates that have hidden figures in them rather than numbers.

Some of the plates may only have numbers or figures that are visible to those suffering from colour blindness, while other plates may contain numbers of figures that appear differently depending on the form of colour blindness that the patient may have.

The colour blind test requires accurate interpretation and conditions to perform; therefore it is highly recommended for you to have it done formally with an optometrist during your next eye exam.  Usually this can be bulk-billed.

Colour Blindness Treatment

There is no treatment for congenital colour blindness; however it is important to let educators know about a child’s colour blindness to ensure they won’t be disadvantaged in class.  This may involve the teacher using different patterns and borders in graphs and figures to highlight separate groups of data rather than using colours.
For acquired forms of colour blindness, it may be treated by managing the underlying causes of the condition.

There are special glasses and contact lenses that are marketed to treat colour blindness by creating a difference in brightness between confused colours to tell them apart, however their benefit depends heavily on the severity and type of the colour vision deficiency as well as the task at hand.

Where can I find more information?

For a more in-depth look at colour blindness and colour blind tests, you can visit

You can also click here to visit the Colour Blind Awareness and Support Group of Australia.

Click here to book a colour vision test at Eyecare Plus Corrimal.