Tritanopia: Definition, diagnosis and prevalence

What is tritanopia?

Tritanopia is a rare form of “blue–yellow” color blindness. Despite the description, tritanopia does not make it difficult to tell the difference between blue and yellow but colors that contain blue or yellow. Difficulties lie between green–blue, yellow–pink and purple–red. 

Though tritanopia confuses color perception, and colors may seem less bright, it does not affect the clarity or sharpness of your vision.

What is color blindness?

Color blindness is a condition that makes it difficult to tell the difference between certain colors. Another more accurate name for the disorder is color vision deficiency as it is extremely rare for anyone to be entirely colorblind.

Humans see color because they are born with three types of light-sensing cones in their eyes. Each type of cone is sensitive to light of different wavelengths. Those wavelengths are red, blue and green. If our cones are missing specific light-sensitive pigments, it is harder to see colors associated with those pigments.

The most common form of color blindness is red–green color blindness, followed by blue–yellow color blindness. About 1% of people have blue–yellow color blindness, and both men and women are equally affected. Rarely, some people have complete color blindness and see  the world in grayscale.

READ MORE: Types of color blindness

What causes tritanopia?

In tritanopia, the cones of the eyes that are sensitive to short wavelengths (S-cones) are missing. Without S-cones it is difficult to distinguish between colors that have either blue or yellow in them.

There are actually two forms of blue–yellow color blindness:

• Tritanopia, which makes it difficult to distinguish between colors containing blue or yellow, such as green and blue or and purple and red. Individuals with tritanopia are missing their S-cones.

• Tritanomaly, which causes difficulty distinguishing between green and blue, and red and yellow. Individuals with tritanomaly have defective S-cones caused by a gene mutation.

Is blue–yellow color blindness severe?

Blue–yellow color blindness can be a more serious form of color deficiency because some may also have red–green color blindness. In either case, people with blue–yellow color deficiency may see spots of gray or a neutral shade in place of certain colors.

However, those with tritanopia seem to have less difficulty performing routine tasks than those with red–green color deficiency. This is likely because red and green are more often assigned to daily signals such as “stop” and “go” or “off” and “on.”

Traffic lights use red and green. Many warning lights as well as stop signs are red. Green lights often indicate an appliance is turned on, while red lights indicate it is off. Yellow and blue are not as commonly used for signals.

How common is tritanopia? 

Blue–yellow color deficiency affects men and women at equal rates. However, tritanopia and tritanomaly are quite rare, found in only 1 out of 10,000 individuals. Color vision deficiency is most common among Caucasian males and is least common among African-Americans. A study of 4,177 children in preschool in the U.S. found that 5.6% of non-Hispanic Caucasian boys had color-blindness, while 3.1% of Asian boys, 2.6% of Hispanic boys and 1.4% of black boys had the condition. Only about 0.5% of girls were colorblind.

Can tritanopia be acquired?

Tritanopia is generally a genetic condition and present from birth. However tritanopia can also be acquired in one of the following ways: 

• Cataracts. As you age, the lens of your eye can become cloudy as a result of cataracts. This can cause a very mild tritanopia, which can be reversed with cataract surgery.

• Macular Degeneration. This is an eye condition that occurs more often in older adults and leads to loss of central vision. As a result, loss of blue–yellow sensitivity can occur.

• Alcoholism can lead to tritanopia. It is thought that large amounts of alcohol can be toxic to the inner layers of the retina. As a result, sensitivity to blue and yellow can become impaired. 

• Workers exposed to low concentrations of organic solvents had impaired blue–yellow vision. 

• Traumatic brain injuries can occasionally cause blue–yellow color blindness.

• Diabetes can damage the retina and thereby lead to blue–yellow color blindness.  

How is tritanopia diagnosed?

To diagnose tritanopia, a person will be given a color blind test. The most popular is the Ishihara Color Vision Test, invented by a Japanese ophthalmologist more than 100 years ago. 

A patient is asked to look at a series of dots. A number will appear among the dots. But that same number will be hard or impossible to see for people with tritanopia. In some tests, the colors are combined in such a way that a person with tritanopia will see one number, while a person with normal vision will see a different number. 

The Farnsworth-Munsell 100 Hue Test is also popular. The individual is asked to arrange colored disks in a continuous sequence of color changes. Individuals with tritanopia will not be able to properly arrange the disks because they cannot tell the colors apart.

These tests allow the eye doctor to determine whether someone experiences color blindness, and if so, what kind.

What are good coping strategies for living with tritanopia?

Though tritanopia can be frustrating, individuals can live essentially normal lives with the condition. Some ways to make life a bit easier may include:

• Organize and label clothing, or other colored objects needed for daily life. This will help you easily identify what you’re looking for. Labelling clothes allows you to match outfits properly. You can do this with the help of a friend or family member.

• Memorize the order of certain things rather than their color. For instance, a traffic light goes red – yellow – green, from top to bottom. 

• Since colors look less bright to those with tritanopia, be sure the lighting in your home is bright. The darker the room, the harder it is to distinguish colors.

Are there treatments for tritanopia?

Specially tinted eyeglasses designed for the color blind are available. These glasses may help some people with tritanopia see the world more vividly and colors more accurately. 

Colorblind glasses contain optical materials that filter specific wavelengths of light. While wearing these specially tinted lenses, vision should be closer to “normal,” allowing the wearer to see a broader array of colors. 

Colorblind glasses look a bit like sunglasses and can be either prescription or nonprescription. Colorblind glasses can cost anywhere from $200 to $450, sometimes more.

Color correction eyewear brands that claim to help tritanopia include Golden, Vino and ColorCorrection. Some may simply improve contrast, rather than change how colors are perceived. 

The ColorCorrection System was developed by a Maryland optometrist, Thomas Azman, MD. ColorCorrection offers glasses or contact lenses that use filters to create customized lenses. These lenses are manufactured according to each individual’s color correction needs, according to Azman’s website, Colormax.

Though there is no cure for any kind of color blindness, there may be a more permanent treatment one day. Gene therapy has cured red–green color blindness in monkeys, and perhaps someday there will be a cure for all types of color blindness in humans.

Tritanopia, like other forms of color blindness, is not a serious threat to vision. And with a few adjustments, you can function and move through life as anyone with normal color vision.

READ NEXT: Tips for better living with color blindness

Page published on Wednesday, August 25, 2021