Diagnosis and Treatment of Color Vision Deficiency (Color Blindness)

Diagnosis

Tests for color vision deficiency can be divided into screening tests, severity assessment tests, confirmatory diagnostic tests, and occupational aptitude tests, depending on their purpose. The specific types of each test are as follows.

1. Pseudoisochromatic plate test

Pseudoisochromatic plates are test charts arranged with dots of similar colors alongside dots of the same color so that numbers or shapes composed of the same color dots are easy to confuse. People with normal color vision can easily identify the numbers or shapes, but in people with color vision deficiency, the form may not be recognized or may be confused with another number because of blending with the surrounding colors.

1. Ishihara color vision test

First created in 1917 by the Japanese ophthalmologist Ishihara, and revised several times since then, this is now the most widely used color vision test worldwide. It is easy to carry and simple to administer, so it is convenient to use, and it is an excellent screening test with high sensitivity (90–95%) that can detect most cases of color vision deficiency. However, because there are rare cases in which a person with normal color vision is judged to have color vision deficiency (false positive) or a person with color vision deficiency is judged to be normal (false negative), this should be kept in mind when using the test.

Depending on the number of plates, there are 38-, 24-, and 14-plate versions, and they can detect type 1 and type 2 color vision deficiency, that is, red-green color vision deficiency, but cannot detect type 3 color vision deficiency. In general, type 1 and type 2 color vision deficiency cannot be distinguished, but the 38-plate version includes diagnostic plates that can differentiate between the two. There are also tracing test plates for children and adults who cannot read numbers, but they cannot distinguish the degree of color vision deficiency, such as mild, moderate, or severe.

2. H-R-R color vision test

This test detects three shapes—a circle, triangle, and scissors—and can be applied to children and adults who are not familiar with numbers. It consists of 24 color plates and is not as sensitive as the Ishihara test for detecting color vision deficiency, but it can also detect type 3 color vision deficiency, which the Ishihara test cannot. Therefore, it is also useful for diagnosing acquired color vision deficiency. It is designed to assess the degree of severity as well, from mild to moderate to severe.

2. Color arrangement test

This is a color vision test in which a series of color chips arranged in color order are first mixed at random and then rearranged into the original order. It makes it possible to classify color vision deficiency and assess its severity. About 50% of people with congenital color vision deficiency pass this color arrangement test without difficulty, so the purpose of this test is not to determine whether color vision deficiency is present, but rather to classify it into type 1, type 2, and type 3 color vision deficiency and assess its severity.

1. FM 100 color test

This method measures whether adjacent colors can be distinguished by dividing 85 different color chips into four boxes and having the person arrange them in color order. The error value increases as chips that are not recognized are incorrectly identified and placed next to similar colors, and the total error value and its pattern can be used to judge the type and degree of color vision deficiency. Although the test takes relatively a long time to administer and analyze, it has the advantage of allowing precise quantitative assessment of the severity of color vision deficiency, and it can also be used to test for type 3 color vision deficiency, making it useful for diagnosing and following up patients with acquired color vision deficiency.

2. Panel D-15 test

After arranging 15 color chips in color order, the numbers marked on both sides of the chips are connected on a recording sheet starting from number 1, and color vision deficiency is judged based on the arranged pattern. If two or more crossing return transverse lines appear in the recording sheet diagram, the test is judged as a failure, and it can be determined that there is moderate or more severe color vision deficiency. Mild color vision deficiency passes this test just like in normal individuals. Depending on which direction of the guide line axis on the recording sheet matches the transverse line, the condition is classified into type 1, type 2, and type 3 color vision deficiency.

3. Anomaloscope test

The anomaloscope test is the standard test for all color vision tests because it is sensitive and gives the most accurate results for diagnosing, classifying, and assessing the severity of congenital color vision deficiency. The examinee mixes the red and green in the upper semicircle appropriately to match the yellow in the lower semicircle inside the anomaloscope, thereby diagnosing color vision deficiency. However, it has the disadvantages of being difficult to use, requiring a highly skilled examiner, taking a long time, and involving expensive equipment, so its use in practice is very limited. It cannot be used for type 3 color vision deficiency or acquired color vision deficiency; it is only intended for congenital type 1 and type 2 color vision deficiency. There are two models of anomaloscopes: Nagel and Neitz.

4. Signal light test

The signal light test is used for occupational aptitude assessment in specific professions, and it is used to determine whether people working in railway, shipping, and aviation jobs have the ability to identify actual signals. The three-color light test conducted when obtaining a driver’s license is also a type of signal light test based on occupational performance ability assessment.

Treatment

Because color vision deficiency is congenital and involves a problem with cone cell function, definitive treatment is not yet possible. However, tinted contact lenses or glasses can partially correct color vision deficiency, such as by helping match the Ishihara pseudoisochromatic plates. In other words, rather than improving color discrimination itself, this method enhances the contrast between two adjacent colors, making one appear brighter and the other relatively darker, thereby increasing the difference in brightness and lightness so that the two colors can be distinguished more easily.

As a result, actual color perception may even decrease. Contact lenses that can currently be purchased on the market have been approved by the food and drug safety authorities of major countries. They are available in different types using 7 to 8 colors, and the most effective lens color can be selected by directly testing the person with color vision deficiency. Magenta is used most often. However, this method does not help everyone with color vision deficiency, and it should be selectively applied only when the ability to distinguish the relevant color is very important for that person’s work or daily life. In fact, these lenses may interfere with other aspects of daily life or work, so it is best to make a very careful decision after consulting an ophthalmology specialist and undergoing testing.

So far, we have explained the diagnosis and treatment of color vision deficiency (color blindness).

In the next article, we will look at congenital hypothyroidism.

Source: Korea Centers for Disease Control and Prevention, National Health Information Portal