Color vision is the ability of our eyes to work together with our brain to perceive the properties of light. Color vision test checks for the inability to distinguish colors or (rarely) any colors at all. This condition is known as color vision deficiency (CVD). It is also known as color blindness.
Not all people with CVD see the world in black and white as commonly misconceived. Most tend to see as clearly as other people do but are not able to fully see colours. It is only in exceptional cases that people don’t see any form of color.
There are approximately 330 million people worldwide with color vision deficiency. Men have been proven to be more color blind than women with 1 in every 12 men as compared to 1 in every 200 women being color blind. Color-blind people sometimes don’t know they are suffering from the condition. Due to this, they usually have a hard time in their day-to-day activities, for example, differentiating between red and green traffic lights.
The perception of color involves the retina, where there are three types of cones. Each of them is sensitive to different visual pigments and is responsible for color detention. When all three of these cones gather the information together, this makes up color vision.
- The L Cone – Detects red hues.
- The M Cone – Detects green hues.
- The S Cone – Detects blue hues.
Also Known As
- Ishihara color blindness test
- Color perception test
Testing for color vision deficiency is not complicated; one can even conduct it at home or online. However, for more accurate results, it is recommended that the test be carried out at an eye clinic by:
- An optometrist
- An ophthalmologist
There are two causes of CVD:
1. Inherited Color Vision Deficiency
Genetics is the leading factor for color blindness. The disease is passed on from a parent to their child through the X chromosome.
2. Acquired Color Vision Deficiency
Some people also get CVD through:
- Chronic diseases such as glaucoma, Alzheimer’s diseases, leukemia, multiple sclerosis, some liver diseases, sickle cell anemia macular degeneration, and Parkinson’s disease.
- Accidents or strokes.
- Medicine such as antibiotics, hypertension medication, and anti-tuberculosis drugs.
- Advanced age.
A color vision test is essential, especially for anyone considering going into a line of work where color differentiation is paramount. Examples of these professions include pilots, astronauts, drivers, electricians, and technicians. Young children should get tested. This is because those who acquire color vision deficiency are not able to know whether or not they are color blind. The defect can interfere with their formative learning and day-to-day activities.
Preparation & Expectation
There is no prior preparation required when taking a color vision deficiency test. One can resume their normal activities after the test is complete. The patient is expected to take with them their glasses or contact lenses to the doctor’s office.
- Ishihara plate test/pseudoisochromatic plates
- Arrangement tests
- Lantern tests
The most commonly used test is the Ishihara Color Blindness Test. It tests red-green color vision defects but not blue color vision deficiency.
This test is made up of 38 individual pages/plates which have a pattern of dots that create a number in the middle of the plate. These irregularly colored dots appear varying brightness, various colors and sizes. The test is conducted in a well-lit room. Each eye is tested individually and if the patient wears glasses, they will be required to put them on. The examiner will then put the plates in front of the patient and ask him/her to identify what number they observe.
Some plates contain numbers which only trichromats can see, while others have content that only people with color blindness will see. According to the number of errors one makes, the examiner will conclusively be able to diagnose whether or not the patient has color vision deficiency.
To test color vision deficiency in young children who can’t identify numbers yet, unique variations have been created with patterns.
According to the answers given by the patient, the eye specialist will be able to diagnose the specific type of color vision deficiency the patient has. Trichromacy is the term used when a person uses all three of their eye’s cones correctly.
The types of CVD include:
1. Anomalous trichromacy
This is the most common type of CVD. People who have one impaired light cone that wrongly perceives light are known as anomalous trichromats.
This is where a person only has two cones which can correctly see color, while the other one is completely missing. These people are known as dichromats.
Dichromats and anomalous trichromats occur in three different types according to the missing or malfunctioning cone.
- Protanopia – This is the malfunctioning L-cone, which results in reduced sensitivity to red lights.
- Deuteranopia – This is the most common form of color blindness, which is caused by the malfunctioning of the M-cone, resulting in low sensitivity to green light.
- Tritanopia – This occurs when there’s a malfunctioning S-cone, which results in reduced sensitivity to blue lights. This is extremely rare.
People with protanopia and deuteranopia have trouble telling the difference between reds, browns, greens and oranges. People with tritanopia can’t differentiate between blue & yellow, blue & green and violet & red.
3. Monochromatism (Achromatopsia)
This is where a person has no cones available to perceive color. These people have total color blindness. They see in total shades of black, white, and grey. This condition is rare, with only 1 out of 33,000 diagnosed with it.
The doctor will discuss the results of the test with the patient and explain the appropriate treatment. Although there is no known cure for color blindness, an eye specialist may be able to prescribe specially tinted contact lenses, which will significantly improve a color-blind person’s ability to perceive specific colors.
Risks & Complications
The color vision test is a simple and straightforward eye exam without any known risks.