The terms red-green deficiency, red-green visual impairment, or red-green blindness are the technical terms for the most common color vision deficiencies, known colloquially as color blindness. Contrary to popular belief, those who are red-green blind are not necessarily incapable of recognizing these two colors; there may also be a weakness in discrimination.
What is red-green deficiency?
Red-green deficiency is a retinal defect that affects approximately eight to nine percent of the male population and only about one percent of the female population. There is a defect in one, two or all of the eye’s receptors responsible for color mediation, resulting in general color blindness or the most common color vision deficiency, red-green blindness. Red-green vision deficiency, also called Daltonism after its discoverer John Dalton. Affected individuals thus suffer from unilateral color vision. They are not able to distinguish between the colors red and green. In addition, they may also have problems differentiating between various other hues if green or red have been added to them. The disease can occur in various forms and is usually not experienced as a hindrance by those affected. In particular, red-green vision deficiency is an obstacle when choosing a profession. Affected persons are not allowed to work in some professions such as sailor, policeman, cab driver or pilot. However, red-green vision deficiency can also be an advantage for those affected, who are more sensitive to gradations of brightness, giving them fundamentally better night vision, and can distinguish khaki tones and shapes and contours better than non-color vision deficient individuals. The military likes to work with colorblind people to test the effectiveness of camouflage suits.
Causes
The cause of red-green blindness is a genetic change in the cones of the retina. Errors in the transfer of hereditary information to chromosomes create incorrect gene combinations that cause cone dysfunction. The exact processes that lead to red-green deficiency are very complicated and can be found in relevant medical encyclopedias. It is important to know that red-green deficiency is always congenital and is inherited recessively. Scientists suspect a reduced number of cones on the retina with an increased number of rods in addition to the disturbance of the cone function. The rods of the retina are responsible for light-dark vision, which would explain the increased ability of night vision compared to normal-sighted people. To date, however, this hypothesis has not been proven.
Symptoms, complaints, and signs
The leading symptom in the presence of red-green deficiency represents the reduced ability to see the corresponding colors. The ability to distinguish the colors red and green is affected here. However, there are numerous gradations. Thus, a red-green deficiency is not necessarily a color blindness. Rather, the ability to distinguish between red and green can also be impaired. This can happen depending on the exact hue. For example, certain shades of red and green may be indistinguishable for the affected person, while other shades may be clearly distinguishable for him or her. As a result of the restriction in seeing red and green, the affected person perceives significantly fewer different shades of color. The more the perceived wavy lines overlap in the corresponding cones of the eyes, the more difficult it is for the affected person to distinguish red and green. The colors are described by most affected persons as shades of gray or brown. In any case, both eyes are affected and the disease persists throughout life. Due to the fact that most affected persons have not experienced correct color vision at all, there are hardly any limitations. The other vision is not limited. Those affected by red-green deficiency can also compensate for their limited color vision. This is accomplished by classifying the perceived shades of brown or gray or by the sheer knowledge of what color an object should be.
Diagnosis and progression
Self-testing for red-green vision impairment has been easy since the introduction of the euro in the European Union, as physicists at the Universidad de Extremadura in Cáceres discovered: Anyone who cannot distinguish between the colors of the 5- and 20-cent coins is almost certainly red-green-blind.Since those affected are also unable to distinguish shades in which there is a high red or green component, they are unable to objectively distinguish between these two coins. However, ophthalmologists naturally have more far-reaching diagnostic methods at their disposal to diagnose not only red-green deficiency but also its severity. The most commonly used are the Ishihara color charts, the Farnsworth test, and the spectral color mixing apparatus. The task on the spectral color mixing apparatus is to set a yellow circle based on color mixtures, whereby color vision deficiencies quickly become apparent. This complex test is a typical test of professional aptitude. Simpler testing for ability to discriminate colors is done using the Ishihara color charts, on which numbers are shown in colored blobs, and using the Farnsworth test, which gives the subject the task of color matching.
Complications
There are no real complications in the medical sense in the presence of red-green deficiency. It is an actual condition in the eye that does not imply any organic impairment and does not imply any increased risks for any diseases in the eye area. Complications in the broadest sense only arise for those affected if their color vision deficiency specifically restricts them. This may be the case, for example, when choosing a profession where correct color vision is necessary, for example, as a pilot or in the course of technical laboratory examinations. Whether this significantly affects the affected person is an individual question. Most of those affected, however, are able to come to terms with their red-green weakness very well – if only because they do not know it any other way. When driving at night, however, red-green deficiency can mean an increased risk of accidents. After all, it is very difficult for people with red-green vision impairment to see red lights in poor light. Furthermore, occasionally very concrete problems arise in everyday life. For example, the colors red and green are often used to distinguish or mark elements (text, picture, toys, etc.), signage, and numerous everyday objects as well.
When should you go to the doctor?
People who notice visual impairment should always consult a doctor. The extent of the visual disturbance as well as the cause of the complaints must be clarified. A diagnosis is needed so that a suitable treatment plan can be developed. Blurred vision, problems in recognizing moving objects or abnormalities in color perception should be discussed with a doctor. If inconsistencies in vision can be determined in direct comparison with people in the immediate environment, the affected person needs various tests to clarify the complaints. A direct exchange with other people in everyday life helps to assess the existing problem. It should be used as a basis to be able to describe any irregularities noticed to the doctor as accurately as possible. If adults notice behavioral abnormalities or peculiarities in the color descriptions of objects in their offspring, they should consult a pediatrician together with them. By their very nature, children cannot become active on their own and should therefore be presented to a physician. Since red-green deficiency can lead to considerable problems, especially in road traffic, the affected person is subject to an increased risk of accidents. If developments occur that substantiate the suspicion of a color perception disorder, a visit to the doctor should be made as soon as possible. Many sufferers do not notice the disorder for a long time. As soon as there are indications and suspicions, a medical consultation is advisable.
Treatment and therapy
Because affected individuals with red-green vision loss are able to manage their lives very well and rarely experience limitations in their daily activities, no therapy is usually necessary. Therefore, no treatment options applicable in humans have been developed so far. Another reason for the lack of therapy options is the interest of science in color blind people, as they can be used to test theories on the development of human vision. In 2009, British researchers succeeded in using gene therapy to induce the ability to recognize the entire color spectrum in red-green-blind squirrel monkeys. The research team hopes that these results will lead to therapeutic approaches to cure color vision deficiencies and possibly even blindness.
Prevention
There is currently no known prevention of red-green deficiency, as it is a congenital disorder. On the other hand, red-green deficiency is also not considered a disease or ailment that can severely hinder a normal and healthy life. From this point of view, prevention of red-green deficiency is not necessary.
Aftercare
Red-green deficiency is not curable and cannot be prevented. It affects the patient throughout life in various aspects of daily life. For this reason, consistent care by an ophthalmologist is necessary to make it easier to integrate the visual impairment into everyday activities. An improvement or cure of the symptoms, on the other hand, is the exception in the case of red-green weakness. This is especially true if the visual impairment is congenital. Surgery is also not possible. However, if a specialist discovers red-green deficiency at an early stage, it can be treated satisfactorily. This is primarily the case with non-congenital red-green deficiency. Follow-up care should improve the quality of life of the affected person. This concerns not only the visual ability, but also the psychological condition. If the patient perceives his red-green deficiency as very stressful or limiting and suffers from it, parallel psychological care is advisable in addition to ophthalmological control. In this way, the development of depression can be prevented. Particular attention should be paid during follow-up care to the patient’s ability to drive, since red-green deficiency can considerably restrict the patient’s ability to participate in traffic. Driving a car is sometimes out of the question. To better cope with these and similar limitations, appropriate exercises are necessary, which the ophthalmologist performs with the red-green-blind person.
This is what you can do yourself
People with red-green deficiency can use special lenses that expand or filter the color spectrum. Because these lenses alter color perception, they may not be used while driving or working on certain machines. Some color correction glasses are custom-fitted to the degree of refractive error, which can almost completely correct red-green deficiency. People who suffer from total color blindness may need dark sunglasses. These special glasses have special edge filters that filter certain colors and intensify others. This enables sufferers to read small print and see colors that were previously invisible due to red-green deficiency. Patients suffering from red-green deficiency usually require assistance in everyday life. The help of friends or acquaintances is particularly useful in road traffic and for fine work. Accompanying the patients should regularly consult the ophthalmologist. Mentioned special glasses are only one of many current developments, which could make an almost normal color perception possible in the future. Depending on the degree of color vision deficiency, the choice of profession must be reconsidered. For example, sufferers usually cannot become pilots or train drivers.
