Color blindness, also known as color vision deficiency, is the decreased ability to see color or differences between colors. It affects a significant percentage of the population and can range from mild to severe. But is it possible to be completely color blind, unable to see any color at all?
What is color blindness?
To understand if total color blindness is possible, it’s important to first understand what causes color blindness. The retina of the eye contains two types of light-sensitive cells called rods and cones. Rods allow you to see in low light conditions, while cones allow you to see color.
There are three types of cones, each responsive to different wavelengths of light that our brains interpret as red, green or blue. When one or more of these cone types is absent or not functioning properly, it leads to color vision problems.
The most common types of color blindness are:
- Red-green color blindness – caused by absent or faulty red or green cones.
- Blue-yellow color blindness – caused by absent or faulty blue cones.
- Total color blindness (achromatopsia) – caused by absent or faulty cones of all three types.
What does it mean to be 100% color blind?
Being 100% color blind means having complete achromatopsia with no functioning cones. This means you are unable to perceive any color and see the world entirely in shades of grey.
Complete achromatopsia is very rare, affecting approximately 1 in 30,000 people worldwide. Those with the condition have extreme light sensitivity and usually very poor visual acuity. They see the world as if it were a black and white movie.
Is complete achromatopsia possible?
Yes, it is possible but very rare for someone to have complete achromatopsia with no color perception at all. This occurs when all three cone types are completely absent or totally non-functional.
Some key points about complete achromatopsia:
- Caused by genetic mutations leading to absent or non-functional cones.
- People have no ability to distinguish colors, only shades of grey.
- Other visual problems like light sensitivity, poor acuity and nystagmus often present.
- Onset is usually at birth or in early infancy.
- No treatment exists to restore color vision.
Although extremely rare, there are verified cases of people with complete achromatopsia and no cone function whatsoever. They see no colors at all and have complete color blindness.
What causes complete color blindness?
In most cases, complete achromatopsia is caused by mutations in genes important for cone development and function. The key genes associated with complete achromatopsia are:
- CNGA3 – encodes a subunit of the cyclic nucleotide-gated channels in cones.
- CNGB3 – encodes a subunit of the cyclic nucleotide-gated channels in cones.
- GNAT2 – encodes a cone-specific enzyme important for phototransduction.
- PDE6C – encodes a cone-specific enzyme critical for phototransduction.
- PDE6H – encodes a cone-specific enzyme critical for phototransduction.
- ATF6 – encodes a transcription factor involved in development of cones.
Mutations in these genes can lead to either absent or non-functional cones from birth, resulting in complete inability to see colors.
Prevalence of complete achromatopsia
Complete achromatopsia is one of the rarest types of color blindness. Estimates of its prevalence include:
- Affects 1 in 30,000 people worldwide.
- 1 in 33,000 people in the United States.
- Equal rates in males and females.
- Higher rates in populations where consanguineous marriages are common.
Due to its rarity, large epidemiological studies are lacking. But available data indicates complete achromatopsia affects a very small fraction, around 0.003%, of the population.
Living with complete color blindness
Living without any color perception is challenging but those with complete achromatopsia adapt in various ways:
- Use shades of grey and texture for identification.
- Rely more on other senses like hearing and touch.
- Get assistance from devices like color identifiers, text readers, etc.
- Take advantage of strong low-light vision.
- Avoid bright lights which cause glare and pain.
- May have reduced visual acuity and use corrective lenses, magnifiers, etc.
With appropriate adaptations and assistive technology, people with complete color blindness can lead productive lives.
Diagnosing complete color blindness
Diagnosing complete color blindness involves specialized vision tests. These may include:
- Ishihara test – Reading number plates detects red-green defects.
- Farnsworth D-15 – Arranging color caps identifies hue defects.
- Anomaloscope – Matching red-green lights detects red-green defects.
- Electroretinography (ERG) – Measures cone response to light.
- Genetic testing – Checks for associated gene mutations.
Those with complete achromatopsia fail all color perception tests and have non-detectable cone responses on ERG. Genetic testing can confirm associated gene mutations.
Is there any treatment?
Unfortunately, there are currently no effective treatments to restore color vision in people with complete achromatopsia. Some options that may provide limited benefits include:
- Tinted lenses – Reduce light sensitivity and glare.
- Low vision aids – Magnifiers to help with visual acuity issues.
- Amblyopia therapy – Patching stronger eye may improve acuity in weaker eye.
- Retinal gene therapy – Experimental with limited success so far.
While these can help with associated visual problems, the inability to see colors remains unchanged.
Coping and outlook
Living without color vision requires significant adaptation. Some tips for coping with complete color blindness include:
- Use other cues like texture and shades of grey for identification.
- Label clothing tags, food items, etc. with shapes or textures.
- Have understanding family, friends and coworkers.
- Explain condition to others to avoid confusion.
- Advocate for accommodations at school and work.
- Employ assistive devices that convert colors.
- Join support groups to share experiences.
With practice and support, most adapt well. Recent advancements in genetic research and assistive technology continue to improve outlook for the future.
Conclusion
Although extremely rare, complete color blindness with no cone function does occur in a small fraction of people. This results in an inability to perceive any colors at all and seeing the world only in greyscale. While no treatments currently exist to restore color vision, many adapt well with appropriate support and accommodations. Increased awareness and additional research provides hope for better treatment options in the future.
| Type | Cause | Prevalence | Features |
|---|---|---|---|
| Red-green color blindness | Faulty red or green cones | 1 in 12 men 1 in 200 women |
Trouble distinguishing red and green hues |
| Blue-yellow color blindness | Missing or faulty blue cones | 1 in 10,000 | Difficulty with blue and yellow shades |
| Complete achromatopsia | No functioning cones | 1 in 30,000 worldwide | No color perception, only shades of grey |
| Gene | Role |
|---|---|
| CNGA3 | Encodes cone channel subunit |
| CNGB3 | Encodes cone channel subunit |
| GNAT2 | Cone phototransduction enzyme |
| PDE6C | Cone phototransduction enzyme |
| PDE6H | Cone phototransduction enzyme |
| ATF6 | Cone development transcription factor |