Red-Green Color Blind Tests

A red-green color blind test detects red-green color blindness. The most common such test is the Ishihara test.

Red-green color blindness makes it difficult for someone to differentiate between red, green, and yellow. Some people with red-green color blindness may not be aware of their condition.

A red-green color blind test can let such people know that they have this form of color blindness so they can take the necessary precautions to stay safe even when they can't tell some colors apart.

This article explains red-green color blindness along with why it happens and the tests used to diagnose it.

Red-Green Color Blindness

Red-green color blindness, also called a red-green vision defect, is the most common type of color blindness, affecting up to 8% of males and 1% of females globally.

This type of colorblindness results from loss or damage to red- or green-sensing photoreceptors in the eye. For people with this form of color blindness, reds and greens look similar to each other, appearing as a brownish, muted tone.

The terms "protan" and "deutran" are often used to refer to red and green color deficiencies, respectively.

That said, there are four subtypes of red-green color blindness:

• Protanopia: An affected person cannot perceive red light at all.
• Deuteranopia: Someone cannot perceive green light at all.
  
• Deuteranomaly: This is the most common red-green color blindness. It makes green appear more red. This type of red-green color blindness is generally mild and covers everything from almost normal vision to deuteranopia.
• Protanomaly: A mild type of color blindness, reds appear more green and less bright.

What Causes Color Blindness?

Color blindness, also known as color vision deficiency, is usually genetic, meaning it is passed on from parents to children. In the retina, light receptor cells called rods and cones transmit signals from the eye to the brain. Rods provide vision in low light, while cones provide vision in bright light and color vision.

There are three types of cone cells—blue, green, and red—and each contains a specific pigment (called an opsin) that is sensitive to different wavelengths of light. Red-green color blindness is caused by genetic changes involving the OPN1LW or OPN1MW gene, which lead to an absence of certain cones or abnormal opsin pigments in the cones that affect red-green color vision.

Some cases of color blindness are acquired. They can arise from diseases involving the retina or areas of the brain involved in processing visual information, as side effects of certain drugs, or from exposure to particular chemicals.

Types of Red-Green Color Blind Tests

Ishihara Test

The Ishihara test is the most widely used test for red-green color blindness. It was created by Dr. Shinobu Ishihara almost 100 years ago. It consists of a set of 38 color-dotted plates (called Ishihara plates) that contain either a number or a path-shaped design.

The test includes the following four types of plates.

• Vanishing design: People with normal color vision will be able to see the design, but people with color blindness will not.
• Transformation design: People with color blindness will see a different design than people with good color vision.
• Hidden-digit design: People with color blindness will be able to see the number on the plate, and people with good color vision will not.
• Classification design: This is used to determine red-and-green color blindness. The vanishing design is used on either side of the plate (one side for deutan defects, the other for protans defects).

The Ishihara test works for most people. However, other tests may be needed in some cases, such as for people whose eyesight is so poor they can’t see any of the image well, regardless of color. The military also uses more specialized testing.

Cambridge Color Test

Combining the principles of the Ishihara test plus new technologies, the Cambridge Color Test uses plates with colored dots like the Ishihara test but the C-shape is a different color than the background. The C-shape, called the target, appears randomly in one of four orientations, and the person taking the test must click on one of four keys to indicate the orientation.

At first, the target includes vivid, bright colors, which help establish the test taker’s reliability in determining the orientation of the C-shape shown. Then, the computer alters the color quality (chromaticity) between the target and background according to the person’s performance. There are longer and shorter versions of this test.

Another version of the Cambridge test used for people with low vision has four plates, but instead of the plates showing dots and a target, they are all of one color. Three of the plates have a neutral, grayish color, and one has a different color. The person taking the test needs to identify the circle with the indicated color.

Lantern Test

A lantern test checks for red-green color blindness by signaling pairs of either red, green, or yellow dotted lights. The person taking the test must then identify each colored dot within a given time frame.

This type of test is designed to imitate actual colored signal systems that are used in certain workplaces. It is frequently used to screen persons employed by certain organizations that require correct recognition of colored signals.

D-15 Test

This test involves arranging a set of colored plates or discs in the correct color-coded order (a continuum of gradually changing hue).

It is especially useful in detecting dichromatic vision, a condition in which a person only has two types of functioning color receptors in their eyes. Additionally, this test can help determine the severity of the color blindness.

Richmond Hardy-Rand-Rittler Test

Also called the Richmond HRR, this test is used to check for red-green and blue-yellow color blindness along with color blindness severity. Many consider the Richmond HRR test to be the most advanced color-vision test available, capable of detecting color blindness with approximately 97% accuracy.

Color Vision Testing Made Easy (CVTME)

This color vision test is a less demanding test designed for children as young as 3 years old. The test can be easily adapted for children with intellectual disabilities. CVTME uses pictures made of colored dots that display simple images, like stars, circles, and squares. It is a fun test for children that can be completed within 60 seconds.

Neitz Test of Color Vision

The Neitz Test is a simple, quick, and inexpensive test that can identify the type or severity of color blindness within minutes and under any kind of lighting. The Neitz test is similar to other tests in that it displays colored shapes within grey dot patterns. Under each visual, users mark what shape they see. If no shapes are seen, the user can be considered color blind.

Farnsworth–Munsell 100 Hue Color Vision Test

Originally created in the 1940s, the Farnsworth-Munsell Color Vision test has been made into several variations. For example, the Farnsworth-Munsell 100 Hue Color Vision test features 100 hued tiles, while the Farnsworth-Munsell D15 Color Vision test features just 15. Farnsworth-Munsell tests are available in physical form, but can also be taken online.

Anomalscopes

Anomaloscopes are also used to test for red-green color blindness. During a comparison test with this instrument, the screen shows two boxes, each of a specific color. The person taking the test will try to match the color of the first box with the color in the second box by turning a knob that controls the first box. This is a fairly simple test, and it should be supplemented with information from other color-blind tests for an accurate diagnosis.

Who Needs a Color Blindness Test?

The American Optometric Association recommends that all children have a comprehensive optometric examination before beginning school, since a lot of learning materials rely heavily on color perception or color coding.

You may also need a color-blindness test if:

• You have a family history of color blindness.
• You have a hard time distinguishing between certain colors or shades.
• Your job requires full-color vision (e.g., artists, pilots, doctors, and firefighters).

Some diseases can cause color blindness, such as glaucoma, age-related macular degeneration, Alzheimer's disease, and multiple sclerosis. The rheumatoid arthritis medication Plaquenil is also linked to decreased color vision.

Consider having your vision checked if you have been diagnosed with one of these conditions, or if you experience any changes in your vision or color perception.

How Do I Check if I Am Color-Blind?

If you suspect you may be color-blind, first schedule an appointment with your healthcare provider or an eye specialist (an opthalmologist or optometrist).

You can find versions of the Ishihara color test and many others online. However, it's important to note that several factors can impact the reliability of the test, including the type of device or monitor you are using and whether it has a blue light filter.

Summary

Most people adjust to red-green color blindness without any serious issues. If you suspect that you may have this form of color blindness, ask your eye doctor for a test. The test you are given may depend on your age or occupation. The final results will help your provider determine the severity of color blindness you have, and whether it is inherited or acquired. It will also help them determine which technologies, if any, will be beneficial for improving your eyesight.