Color Blindness

 What Is Color Blindness?

Color blindness is a common condition in which you have difficulty distinguishing between certain colors. A more precise term for color blindness is color vision deficiency. 

Color blindness can be inherited or acquired. Inherited means the condition is passed on through genes and present at birth. Acquired means the color blindness occurs later on in life and results from age, eye disease, eye injury, certain medications, or chemical toxicity.

The most common cause of color blindness is an inherited problem in the development of one or more of the three sets of the eyes' cone cells, which sense color. Among humans, males are more likely to be color blind than females, because the genes responsible for the most common forms of color blindness are on the X chromosome.

Females have two X chromosomes, so a defect in one is typically compensated for by the other. Non-color-blind females can carry genes for color blindness and pass them on to their children. Males only have one X chromosome and therefore always express the genetic disorder if they have the recessive gene. 

Color blindness can also result from physical or chemical damage to the eye, the optic nerve, or parts of the brain. Diagnosis is typically with the Ishihara color test; other methods include genetic testing

What Do Colorblind People See?

Typically, someone who is color blind has trouble seeing the difference between a red object and a green object. In some cases, they also have difficulty seeing blues or yellows. 

Color blindness does not necessarily mean you can only see shades of grey. Depending on the type, most people with color blindness can see color. However, some colors may look faded.

In some cases, people may not be aware they have a color vision deficiency until others point out that they do not see the right color. Or, they may not discover their condition until a doctor tests their color vision.

Different Types of Color Blindness

Our eyes contain photoreceptors called rods and cones. Rods are the cells that sense light and dark. Cone cells are sensitive to the different wavelengths of light and are responsible for color perception. They are divided into three types:

• Red light (long wavelength)
• Green light (medium wavelength)
• Blue light (short wavelength)

A person with normal color vision has trichromacy, which means you have a normal amount of all three cone types. Someone with a color vision deficiency may lack all or some cones:

• Dichromacy means you only have two types of functioning cones.
• Anomalous trichromacy means all three types of cones are present, but one of the cone types does not detect color normally.
• Monochromacy or achromatopsia occurs when only one or none of the cones function normally. 

Generally, those with anomalous trichromacy have milder color vision defects versus those with dichromacy. However, their symptoms can range from mild to severe. 

People with monochromacy or achromatopsia have the most severe color vision deficiencies. They see different colors in shades of grey, similar to an old black-and-white movie.

Red-Green Color Blindness

The most common form of color blindness is red-green. Most people with this deficiency inherit it as a recessive X chromosome linked trait, which means a mother who is color blind or who is a carrier can pass this condition to her child. 

Boys are more likely to inherit red-green color blindness because their mother alone can pass it on. For a girl to have red-green color blindness, her father must also be color blind in addition to inheriting this trait from her mother.

You can also develop red-green color deficiencies from eye diseases that damage your retina or optic nerve.

There are different types of red-green colorblindness:

• Deutan types have a deficiency in green cones. Deuteranopia means a complete lack of green cones (dichromacy). Deuteranomaly means a shift in the color sensitivity of the green cones (anomalous trichromacy).
• Protan types have a deficiency in red cones. Protanopia means a complete lack of red cones (dichromacy). Protanomaly means a shift in the color sensitivity of the red cones (anomalous trichromacy).

Those with red-green color deficiencies tend to confuse purple and blue, as well as green, orange, and red.

Blue-Yellow Color Blindness

The blue-yellow type of color blindness is rare. Most people acquire these deficiencies, but in rare cases, you can inherit them. Some eye conditions that cause blue-yellow color vision defects include glaucoma, optic neuritis, diabetic retinopathy, age-related macular degeneration, central serous retinopathy, and other eye diseases that affect your optic nerve or retina.

The types of blue-yellow color blindness are:

• Tritan types have a deficiency in blue cones. Tritanopia means a complete lack of blue cones (dichromacy). Tritanomaly means a shift in the color sensitivity of the blue cones (anomalous trichromacy).

Tritan types tend to confuse blue and green, as well as orange, yellow, and red.

Blue-yellow color blindness occurs in about 1 out of every 10,000 people and affects men and women equally.

Color Vision Testing

The most common type of color vision test eye doctors use is the Ishihara test. The test plates contain dots in various colors. Typically, there is a number on each test plate, although the dots could be arranged into other patterns. These are called pseudoisochromatic color plates.

Your eye doctor will ask you to identify what you see on each page. Those with color vision deficiencies may not be able to see any number or pattern on a given page.

Another test that uses pseudoisochromatic color plates is the Hardy, Rand, and Rittler (HRR) test. The test looks very similar to the Ishihara test. However, the most significant difference is that the Ishihara test only screens for red-green deficiencies while the HRR test can also screen for blue-yellow color vision problems.

Both of these tests are only screening tools and do not pick up on subtle color vision deficiencies. If your eye doctor suspects a color vision problem, they may administer more sophisticated color vision testing, called arrangement tests.

Both of these tests require the patient to arrange several colored discs in a particular order. The order depends on the color and intensity of the color. Based on the mistakes you make in the arrangement, your eye doctor can determine any color vision deficiencies.

Can This Condition Be Treated?

Currently, there is no cure for color blindness. However, there are specialty lenses that can enhance color vision and minimize any type of color vision deficiency. They are available as glasses or contact lenses. These lenses can be life-changing for patients that have difficulty performing daily activities because of color vision deficiencies. 

EnChroma glasses are specially designed to enhance vision in red-green color deficient patients. They carry a wide assortment of glasses to suit mild, moderate, and severe levels of color blindness.

Colormax is a company that produces contact lenses and glasses for color blind patients. Their ColorCorrection System uses customized filters that are unique for every person. 

These types of eyewear can benefit many patients with all types of color blindness, including:

• Professionals who need to pass color vision screenings at work
• People who play sports 
• Artists, designers, and others who rely on color vision to perform work

Color Blindness FAQs

1. What are the 3 types of color blindness?

Duetan, protan, and tritan are the 3 types of color blindness. Deutan types have a deficiency in green cones, protan types have a deficiency in red cones, and tritan types have a deficiency in blue cones.

2. What causes color blindness?

Genetics is the main cause of color blindness, and most people are born with the condition. However, some age-related eye conditions such as glaucoma, optic neuritis, diabetic retinopathy, age-related macular degeneration, central serous retinopathy can also cause color blindness later in life.

3. How common is color blindness?

Approximately 8% of men and 0.5% of women are born with color blindness.

4. Can color blind people drive?

Yes, color blind people can drive since their vision is usually normal in other ways. For example they can learn to read traffic lights by the position of the light rather than the color.