A Complete Guide to Learn About Protanopia

In this article, we discuss what protan color blindness is and the tests and treatment options available to people with this type of color blindness.

Protanopia is a form of color blindness characterized by a tendency to confuse red and green and a loss of sensitivity to red light. Our ability to see with color vision depends on the presence and function of light-sensitive pigments in the cones of our eyes.

Color blindness, or color vision deficiency, occurs when one or more of these cones are not working. When the long-wavelength sensor pigments in the eyes are missing or not working properly is called protan color blindness.

People with protan color blindness have difficulty distinguishing between red and green.

In this article, we discuss what protan color blindness is and blindness tests and treatment options available to people with this type of color blindness.

To understand what protan color blindness is, it helps to understand how the cones in the eyes create color vision. There are certain substances in the eye cones, so-called photopigments, which perceive different wavelengths of light.

Short wavelength cones (S cones) perceive blue, medium wavelength cones (M cones) perceive green, and long wavelength cones (L cones) perceive red.

When the L-cones are absent or dysfunctional, it results in a type of red-green deficiency known as protan color blindness.

Red-green color blindness affects approximately 8% of men and 0.5% of women worldwide, with the most common form being red-green color blindness.

Color blindness itself is caused by an X-linked recessive gene, which is why men are more likely to be affected than women.

This is because males only have one X chromosome and therefore only need one genetic change for the condition to occur. However, females have two X chromosomes and would therefore require two genetic changes to have condition.

Definition of Protanopia

Protanopia (from the Greek protos: first + an: not + opia: a visual condition) is a congenital form of severe color deficiency (dichromacy) affecting the red-green opponent color system.

Protanopes do not distinguish between colors along a specific direction (protanopic confusion lines) in color space and are able to match all colors using two primaries (unlike trichromats who require three primaries).

Protanopia is linked to the X-chromosome and arises from loss or alteration of the gene encoding the opsin of the long-wavelength (L-) photopigment; this malstructure results in the absence of functioning L-cones in the retina.

Protanopia follows a recessive pedigree pattern, with incidence of ca. 1% in the Caucasian male population.

Types of protan color blindness There are multiple types of color blindness, and each type can differ in how severely it affects someone’s color vision.

Protan color blindness generally causes the eyes to have trouble differentiating between red and green.

The two types of protan color blindness are protanomaly and protanopia.

  • Protanomaly happens when the L-cones are present but don’t function properly. As a result, the eyes perceive red as greener.

  • Protanopia happens when the L-cones are missing completely. Without the L-cones, the eyes have trouble differentiating between green and red. The different forms of color blindness, which include protan color blindness, can range from mild to severe.

For example, protanomaly is milder than protanopia and generally doesn’t cause many problems in daily life.

Protanopia, being the more severe form of red-green color blindness, causes a significantly different perception of red and green.

What a person with protanopia might see? Here’s an image as viewed by a person without color blindness:

Protanopia – Red-Green Color Blindness

Red-green color blindness is split into two different types: Whereas people affected by protan color blindness are less sensitive to red light, deuteranopia or deuteranomly (the second type of red-green color blindness) is related to sensitiveness on green light.

Protans have either defective long-wavelength cones (L-cones) or the L-cones are missing at all. If they are missing it is called protanopia or sometimes red-dichromacy.

Affected persons are dichromats because they have only two working cone types, short- and medium-wavelength, compared to persons with normal vision with three different cone types.

Ratios by Gender

GenderProtanopiaProtanomaly

Male

1.01%

1.08%

Female

0.02%

0.03%

If the L-cones are defective they appear in different intensities. This results in either a stronger or a weaker color blindness.

If L-cones are not missing but defective it is called protanomaly. People suffering from this kind of color blindness are called anomalous trichromats.

Protans have difficulties to distinguish between blue and green colors and also between red and green colors. When comparing the two spectrums you can see that there are different colors and shades of colors which are hard to distinguish for a protanopic person.

So those persons are not only blind on red and green colors but a lot more. This means the well known term red-green color blindness is actually misleading and gives a wrong impression of protan color blindness (and also deutan color blindness).

Protanopia and protanomaly both are congenital color vision deficiencies. Their cause is an unequal recombination in the gene array which is passed on thereafter from parents to their children.

The genes encoding the L-cone photopigments are located on the X chromosome. This chromosome is also called the sex-chromosome, because women have two X’s compared to men with only one X combined with Y chromosome.

If something is encoded on the X chromosome it is called sex linked. Sex linked traits are more often observed on men than women because a woman always has a second X chromosome which can compensate the deficiency.

This unbalance between men and women can be seen in the table above showing the ratios of each kind of protan color blindness.

There are a number of studies which show that color vision deficiencies are a serious risk factor in driving. Particularly protan color blindness reduces substantially the ability to see red lights, regardless of the severity of the defect.

Tests showed that protans were very much over-represented in an accident causing group of drivers mostly involving either signal lights or break lights.

Some scientists estimate that being a protan has associated with it a level of risk of road accident that is equivalent to having a blood alcohol level of between 0.05 and 0.08 per cent.

Because of that for example in Australia you can’t get hold of a commercial drivers licence since 1994 if you are suffering from protanopia or protanomaly.

Tests and diagnosis

A color vision test, or Ishihara color test, uses a series of color plates to test for color vision adequacy. Each color plate contains small colored dots. Some of these colored dots are arranged into a number or symbol in the center of the plate.

If you have full color vision, you will be able to see and identify the number or symbol that is present in the image.

However, if you don’t have full color vision, you may not be able to see the number or symbol on certain plates at all. The type of color blindness that you have determines what you can and can’t see in the plates.

While most eye doctors can provide color blindness testing, there are a handful of major companies that specialize in providing free color vision tests online.

EnChroma, one of the leading companies in producing technology for people with color blindness, has a Color Blind Test available on its website. The test takes less than 2 minutes to perform and will let you know if your color blindness is mild, moderate, or severe.

If you suspect that you have color blindness and feel that you would benefit from an official diagnosis, you can also schedule a color vision test with an eye care professional.

Treatment

There is currently no cure for protan color blindness. However, there are companies that produce equipment for people with color blindness to help improve their daily lives.

For example, EnChroma glasses have been marketed as a way to improve color differentiation and color vibrancy for people with color blindness.

One studyTrusted Source from 2018 evaluated just how effective these types of glasses are in improving color vision in participants.

The researchers found that the EnChroma glasses did somewhat change the perception of colors that the participants could already see. However, the glasses couldn’t improve diagnostic tests nor restore normal color vision.

If you’re interested in taking advantage of the treatment options available for protan color blindness, you can visit your eye doctor to learn more.

Living with protan color blindness

Most people with protan color blindness lead normal lives. However, having color blindness can make certain day-to-day tasks more difficult, like driving, cooking, and using electronics.

Management techniques, such as memorization, lighting changes, and labeling systems, can be a helpful for navigating daily life when you have color blindness.

Practice memorization techniques

Protan color blindness has an especially big effect on driving. Red is a widely used color in traffic signs and signals, from stoplights to stop signs.

Memorizing the order and look of traffic signs and signals can help you continue to drive safely, even with color blindness.

Organize and label your wardrobe

Choosing certain outfit combinations can be difficult with protan color blindness, especially for red and green hues.

For people with more severe color blindness, having a friend or family member organize and label clothing can be a huge help.

You can then use the organization and labeling system to distinguish between different colors, which can help when you’re choosing outfits.

Develop your other senses

Smell, taste, touch, and hearing are four of the senses that help us navigate through our daily lives. Outside of other underlying conditions, people with protan color blindness can still use all of these senses for everyday activities.

For example, even without full color vision, smell and taste can be helpful for tasks like cooking food and choosing fresh produce.

Focus on good lighting

Color vision is dramatically reduced in the absence of proper lighting. People with protan color blindness benefit from good lighting because it can help them distinguish between the colors they already see.

Installing natural lighting and daylight bulbs at home and even at work can be a huge help for people with color blindness.

Use accessibility options

Most electronics, such as phones, TVs, and computers, offer accessibility options for people with color blindness. These options can help adjust certain colors on the screen to make it easier to use these devices.

In addition, there are also some apps on the market that can help people with colorblindness identify colors they may not be able to see.

The bottom line

Protan color blindness is a type of color vision deficiency that occurs when the red-sensing pigments of the eyes are either missing or dysfunctional.

There are two types of protan color blindness: protanomaly and protanopia.

Protanomaly is the mild form of red-green color blindness, while protanopia is the more severe form.

All forms of color blindness, including protanomaly and protanopia, can be diagnosed through a color vision test.

Even if you have been diagnosed with protan color blindness, small changes to your daily routine can help you live a normal, fulfilling life.

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