Can you introduce yourself?
Hello! I'm Professor Junyeop Lee of the Department of Ophthalmology at Asan Medical Center. Recently, there has been a lot of interest in color blindness due to the characters in the drama 'The Glory'. Color blindness, which is the inability to distinguish colors well, is one of the types of 'color vision deficiency'. There are severe types of color blindness where one cannot see the 'colorful world', and there are very mild types of color blindness where there is not much inconvenience. Color vision deficiency can also occur as a result of diseases that cause acquired color vision deficiency. Today, I will explain in detail about color vision deficiencies and when treatment is necessary.
Color blindness, which Jeon Jae-joon and Ha Ye-sol have, is it common?
In fact, color blindness is one symptom that falls under the broad category of 'color vision deficiencies'. If one cannot completely distinguish colors, it is called color blindness, and if one cannot distinguish some colors, it is called color vision deficiency. According to the Korea Disease Control and Prevention Agency, 5.9% of men and 0.44% of women in Korea have congenital color vision deficiencies. In the Western world, 8% of men and 0.5% of women are said to have color vision deficiencies. The reason why more men are affected is that the genetic cause of color vision deficiency is more likely to manifest in men.
Is color blindness a disease? What causes it?
Color blindness is a condition where there is a decreased sensitivity to certain colors, making it difficult to distinguish them. Our eyes have a retina, which contains rods that distinguish brightness and cones that distinguish color. Color vision deficiencies such as color blindness occur when the cones that contain photopigments responsible for color perception are congenitally dysfunctional or absent due to genetic mutations. There are three types of cones: S-cone, M-cone, and L-cone, which absorb light at wavelengths corresponding to blue, green, and red, respectively. If the function of the M-cone or L-cone is impaired, red-green color blindness occurs. If a person has only one type of cone, they have monochromatic vision, which means they perceive only one color as shades of brightness. In such cases, visual impairment, eye strain, and photophobia can occur due to congenital abnormalities.
Why do men and women have different probabilities of inheriting color blindness genes?
The cones in the retina that detect blue light contain pigments located on the autosomes whereas the pigments that respond to red and green are located on the X chromosome, and thus, red-green color blindness is inherited through it. In females, the sex chromosomes are XX, so even if one X chromosome has a mutated gene, symptoms do not appear. Such females are called carriers. However, in males, who have XY sex chromosomes, if there is a mutation on the X chromosome, symptoms will appear. Therefore, the probability of color vision deficiency is higher in males. However, not all color vision deficiencies are inherited through the X chromosome. For example, some cases of achromatopsia are autosomal recessive inheritance, and blue-yellow color vision defects are autosomal dominant inheritance.
What is the possibility of inheriting color vision deficiency? Does Park Yeon-jin also have color vision deficiency genes?
The possibility of inheriting color vision deficiency depends on whether the parents have abnormal chromosomes or not. The inheritance of color vision deficiency exhibits the following characteristics:
1) If a female has color vision deficiency, her father must also have color vision deficiency. This is why we can be sure that Ha Do-yeong is not the biological father of Ha Ye-sol.
2) If a female has color vision deficiency, she inherits the causative gene from both her father and mother. If only the father has color vision deficiency, there is no possibility of symptoms appearing even if the abnormal chromosome is inherited and passed on to the daughter.
Therefore, in the drama, it appears that Park Yeon-jin did not exhibit any symptoms of color vision deficiency, but she did carry the X chromosome with color vision deficiency and passed it on to Ha Ye-sol.
Like in ‘The Glory’, can color-blind people really not distinguish colors at all?
Color blindness refers to a condition where people can see colors but have difficulty distinguishing between colors that are similar in hue.
Especially for colors that are far away or have low saturation and are not clear, color blindness can make it difficult to distinguish between similar colors.
Even the same color can appear different depending on its brightness.
Colors with medium brightness can be distinguished, but if the brightness is very low or high, the original color cannot be recognized.
Jeon Jae-joon and Ha Ye-sol cannot see the red and green lights of traffic signals, cannot recognize green shoes, and cannot even properly color cherry blossoms pink.
It is difficult to distinguish colors when they are mixed, but people with color blindness have the ability to distinguish between individual colors, so they can actually distinguish colors.
How can color blindness be diagnosed?
To test color vision, a pseudoisochromatic plate or a color arrangement test can be used. The color arrangement test involves randomly mixing and then re-arranging a series of color chips arranged in a specific order.
For a more accurate diagnosis, an anomaloscope diagnostic method is used, which uses a color vision test instrument that looks like a microscope to distinguish the ratio of mixed colors in a patient's visual field and diagnose color blindness.
Can congenital color blindness be cured?
Congenital color blindness occurs when the function of the cone cells is impaired from birth.
There is no clear cure for congenital color blindness.
However, as in the case of Jeon Jae-joon from the drama ‘The Glory,’ color vision abnormalities can be assisted through contact lenses or glasses that incorporate color on a supplementary basis.
There are typically 7-8 different colors, and the lens that provides the most effective color for each individual is selected.
However, this does not improve the color discrimination ability itself but rather enhances the contrast between two colors that cannot be distinguished.
It is not helpful for all color vision abnormalities, so consultation with a specialist is necessary, and it should be used selectively for important tasks or activities.
Research is underway to improve the genes that cause color vision abnormalities, but no FDA-approved gene therapy is currently available.
Sudden symptoms of color vision deficiency can occur?! Should I go to the hospital?
Acquired color vision deficiency can also occur due to various diseases that occur in the retina, optic nerve, and cerebral cortex. It is important to quickly detect and receive appropriate treatment for such sudden onset color vision deficiency. Acquired color vision deficiencies have the following characteristics:
First, acquired color vision deficiency can occur even when there are accompanying eye or systemic diseases. These include diabetes, glaucoma, age-related macular degeneration, optic neuropathy, and cataracts.
Second, patients may be able to recognize that they have abnormal color vision on their own.
Third, some patients may experience visual disturbances or neurological symptoms, which may worsen or improve over time.
Fourth, acquired symptoms can also occur due to anti-tuberculosis drugs and other medications.
Fifth, the degree of color vision deficiencies may differ between the two eyes, and there may be differences depending on the range of vision even in one eye.
Acquired color vision deficiencies have the characteristic of having a high frequency of blue color deficiency or blue color blindness, which makes it difficult to distinguish blue color, and may also be accompanied by visual impairment. To identify the underlying disease, fundus examination, visual field examination, and sometimes precise tests such as CT or MRI may be necessary. Although acquired color vision deficiencies cause by disease account for less than 1% of the total population with color vision defects, they should not be overlooked because they can be improved by treating the underlying disease. Therefore, if sudden symptoms occur, it is necessary to go to the hospital and get tested.
Closing Statement
Color vision deficiency is not about certain colors being ‘invisible,’ but rather about them being perceived differently than normal. While some people may experience discomfort due to abnormal color vision function, most people with congenital color vision deficiency live their lives without inconvenience, perceiving the world in their own unique way. We can't know what the world looks like to someone else's eyes unless we could swap them. However, in cases of acquired color vision deficiency, accompanying illnesses can sometimes be the root cause of the problem. If you suddenly experience symptoms of color vision deficiency, it's important to consult an ophthalmologist for early diagnosis and treatment of any accompanying conditions, and hopefully, to alleviate the symptoms of color vision deficiency.