Why the Ishihara Test Is Crucial for Your Vision Health!
Why the Ishihara Test Is Crucial for Your Vision Health!
9 September 2024

Colour blindness or colour vision deficiency occurs when people are not able to identify or differentiate different colours. Men mostly suffer from this problem more than women do. Colour blindness is hereditary and can be passed down from parents to kids rather than develop with time. 

Despite that, many individuals live their entire lives without an inkling that they suffer from this condition. This is because many don’t realize that they see colours differently than what an average person’s sight would perceive. That is why getting a colour deficiency test is very important.

There are many ways to test colour blindness. The Ishihara test is the most common and simple method of them all. Here, we will tell you how easily this test works.

Understanding the Ishihara Colour Blindness Test

The Ishihara test was the invention of Japanese ophthalmologist, Shinobu Ishihara, more than a century ago. Many people rely on this procedure for testing red and green colour deficiencies, mostly in small children. This is a basic test where a patient needs to identify coloured numbers and shapes that are designed within a series of differently coloured small dots.

Other common colour vision tests are needed for colour blindness tests as well. For instance, The City University Test and the Farnsworth D-15 test are used in detecting blue light deficiencies, a colour that the Ishihara test can not cover. 

How does the Ishihara test do its work?

It is very easy to recognize an Ishihara test which is a very common test in children. Ishihara test can pick up these colour deficiencies easily. It requires a book made up of 38 different plates called pseudo-isochromatic plates made by an optician. 

All 30 plates have a circle created by a range of dots of different sizes and colours. Within each circle, there are dots of different colours that usually create a number that you have to recognize. For small children, these can be of different shapes rather than numbers.

Educational Plates

The optician will show you all these plates and ask you to identify each number. Here is how the test works. Out of all these plates, you will first be shown colours that may look equal to your brain but are different. Now, it is your brain and your eye’s job to find out the difference to see the hidden number. 

Those who have normal colour vision can differentiate the fake similarity between the two colours and easily see the hidden number. But, you if find it hard to identify the number in a certain place, that might be the case of color vision deficiency. In that case, your optician will diagnose colour blindness.

Why are plates necessary in the Ishihara colour test?

The Ishihara test requires 38 different plates which are used in identifying and diagnosing color blindness. But each plate has a different purpose. There are many places that an optician uses in the test that exactly specifies a colour vision deficiency. There are six different types of plates that doctor uses in this test.

The test is carried out with a demonstration plate which has a number that all types of color vision can see. Normally, this plate shows the number 12 and is a demo to those taking it. Even if you guess the number correctly, which you most probably will, it will still not count in the scoring of the test.

Vision plates

1. Transformation plates

These are the plates where a person with colour vision deficiency will see a different number than those with normal colour vision. For eg: seeing the number 8 instead of 5. 

2. Vanishing Plates

As the name suggests, vanishing plates are only those who have normal colour vision can see a figure. If a person has a vision deficiency, they will not recognise the number visible in the centre, it vanishes in the middle of nowhere. 

3. Hidden Digit Plates

Hidden digital plates are exactly the opposite of vanishing plates. The figure on this plate will be seen only by those with a colour vision deficiency.

4. Diagnostic Plates

The job of these plates is to find out what type of colour vision a person has and how severe the deficiency is.

5. Tracing Plates

Unlike any other plate, a tracing plate is where a person needs to trace a line within the circle rather than find out a number. If a person has a red or green colour deficiency, they may not be able to follow and trace a line that has orange and red shades or colours.

Common Types of Colour Blindness

Opticians can detect the most common types of colour blindness which are called red-green colour deficiencies (protanomaly and deuteranomaly).

This general term encompasses different types and severities. However, it simply means people are not able to differentiate colours that have red or green as a part of the entire colour. For instance, If someone has a red deficiency, they will surely not be able to find out the difference between blue and purple since they can not identify the red properties of purple.

If that happens, your optician will also want to confirm the deficiency by carrying out a colour arrangement test to confirm the results of the Ishihara test. They might do that for the blue-light deficiency whose other name is tritanomaly, a colour the Ishihara test doesn’t detect.

What causes Color Blindness?

Many kids would develop the red-green colour deficiency and opticians may take an Ishihara test during the children’s eye test to spot this problem early. That being said, colour blindness can happen at any age. It can also develop as a result of some serious health issues like diabetes multiple sclerosis or even glaucoma. 

Being exposed to certain medications and chemicals can also lead to this problem. If you are having any issues with your vision lately, it is highly recommended that you go visit your optician who will carry out the test for you. Just remember that colour vision tests are not parts of our normal eye tests.

Color blindness

Can Online Blindness Tests be Trusted?

There are a few online tests that show a possible issue with your colour vision. However, they are not always reliable and we do not recommend relying only on them because the display settings on your screen can be very different. So, it is best to get the test done via a professional optician.

Colour Vision Test Preparation

It is strictly recommended to wear your glasses or contact lenses if you already wearing them. Make the doctor aware of any medications or supplements, if you have any health issues and if your family members have a history of poor colour vision.

Colour Vision Test preparation is not something to worry about. This simple test has no risks and not much special preparation is necessary.

How does an Optician Conduct a Colour Vision Test?

You will sit in your optician’s room as they prepare for the test. You will be asked to cover one eye and then look at a series of test cards with your uncovered eye. As mentioned above, each card has a multicolored dot pattern.

It's your turn to get introduced to each plate that has a symbol or number in each pattern. You need to tell the doctor what you see in the colored pattern.

Test for Color Vision Deficiency

If you have normal colour vision, you can easily distinguish the numbers, shapes, and symbols. However, if you are suffering from colour deficiency, you might not recognize the numbers or symbols. 

You may also have trouble differentiating patterns among the dots. After one eye check is completed, you will do the test on the other eye. Now, you need to cover the other eye look at the test cards and follow the same pattern as before. 

During the process, the doctor might also ask you to describe some colour intensity that you see from two different eyes. While one may still get a normal result on this test, one may still experience some colour intensity loss in either eye.

What do the Test Results Indicate?

The Ishihara test can help identify some vision problems, like:

Types of Color Blindness

1. Protanopia: 

This is an issue where a person can not distinguish blue from green and red from green.

2. Tritanopia: 

This is a difficulty where a person can not separate yellow from green and blue from green.

3. Deuteranopia: 

This is a vision problem where a person can not separate red from purple and green from purple.

4. Achromatopsia: 

This is the rarest of the conditions of complete colour blindness in which one can only see shades of grey.

Can We Treat Colour Blindness?

Unfortunately, no treatment can directly cure these vision problems. But if the colour vision deficiency is the result of a health problem, treating these may improve your color vision as well.

Other things that might be helpful are using coloured filters on your eyeglasses or using coloured contact lenses. They might make colour contrasts easier to see. These things can only help you to a limit as they can not improve your ability to tell colours differently.

Conclusion

Colour blindness does affect a person’s vision to some limit but it is not a painful issue. You must not let this affect the quality of your life. 

Some people who are suffering from colour blindness may experience problems like not noticing if a mango is ripe enough to consume or if their skin is getting sunburnt. If you have some other health issues that are the cause of your colour blindness, you can treat the condition and improve your vision quality by going to the near eye clinic & consult with an opthalmologist.

FAQs

1. Is there any alternative test to the Ishihara test?

Ans: One popular alternative to the Ishihara test is the Dvorine colour-blind test which will determine if a person is suffering from colour vision deficiency. It is rather a simple and quick test that requires more colour plates than the Ishihara test. However, many consider this test somewhat easier to pass than the Ishihara test.

2. What distance is needed for conducting the Ishihara test?

Ans: The room must have proper lighting and phone brightness. If a person wears glasses or lenses, they must continue wearing them. The plates must be held at a comfortable reading distance that is 30 inches or 75 cm.