What Causes Color Blindness?
A 9-month-old female came to clinic for her health maintenance visit. As part of the interview the physician asked if the parents had any concerns about her hearing or vision.
The father said no, but that he had a family history of color blindness and was wondering if she needed to be tested for it.
The family history revealed that the father’s brother and maternal uncle both were red-green color blind.
The pertinent physical exam revealed a developmentally normal female with growth parameters in the 10-50%.
Her visual acuity was grossly normal by fixing and following objects appropriately, and in viewing a book in her lap.
She had normal extra ocular movements bilaterally and her optic disc margins were sharp and the blood vessels appeared normal.
The diagnosis of a healthy female was made and after reviewing a PUBMED literature search, the physician told the parents that it was most likely that the daughter did not have red-green color blindness because it was an X-linked genetic disease and the father himself usually would have to be affected.
The parents were also told that there were potentially other inherited forms as well but that testing at this time was not possible and that as she grew older the testing would be more reliable.
The parents were told to treat her like a normal child and to bring any concerns about her vision including possible color problems back to the physician’s attention.
Color blindness or impaired color vision is common. Red-green color impairments affect 6-10% of males and 0.4 – 0.7% of females.
Screening is often done using Ishihara charts which are pictures of various size spots with hidden wavy lines or numbers. The lines or numbers are read differently by those affected or may not be able to be read at all.
They can be used for children as young as 4 years. The wavy line charts have a higher incidence of errors, but are also more commonly used with younger children. Five errors or more on the first 13 Ishihara plates necessitates referral for additional testing.
Sometimes matching colors can be used in young children but it is not very reliable.
Colors are used in all types of teaching and therefore a child or adolescent may have some problems with the instruction methods used from pre-school through secondary education.
The impact for an individual child varies. Some studies have shown that children with other learning difficulties may have a higher or lower rate of impaired color vision.
Even in the field of art, there are several well known artists who were affected including Carriere, Léger, Whistler and possibly Constable and Mondrian.
Impaired color vision may have an affect on the type of career opportunities available to these children. In the United Kingdom, people are advised against certain occupations including electrical work, electronics, fabric industry, navigators, pilots, train drivers, and certain jobs in the armed forces and police.
The British Paediatric Association recommends screening at age 5, and at 11-12 years or up to 14 years. The American Academy of Pediatrics does not have a recommendation regarding color vision screening.
There are 3 primary color cones in the eye – red, blue and green. When gradiations of the different cones are activated, different colors are seen. For example, orange light mainly stimulates red cones and stimulates some green cones.
Depending on which cone system is defective, these are termed protanopia (red), deuteranopia (blue) and tritanopia (green). Usually one of the cone systems is affected, but there can also be a diminished response by the cones to the color stimuli.
Impaired color vision is mainly caused by an X-linked recessive inheritance pattern. Women (8%) are carriers and males are mainly affected. There can also be complex forms where mosaicism can be found and also an incompletely autosomal dominant form.
Questions for Further Discussion
1. How common is blindness in children?
2. What different methods are available for screening for visual defects in children of different ages?
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
To view current news articles on this topic check Google News.
Gordon M. Colour Blindness. Public Health. 1998;112:81-84.
Committee on Practice and Ambulatory Medicine, Section on Ophthalmology
Eye Examination and Vision Screening in Infants, Children, and Young Adults.
Pediatrics. 1996;98:153-157. Available from the Internet at http://aappolicy.aappublications.org/cgi/reprint/pediatrics;98/1/153 (rev. 1996, cited May 11, 2006).
ACGME Competencies Highlighted by Case
1. When interacting with patients and their families, the health care professional communicates effecively and demonstrates caring and respectful behaviors.
2. Essential and accurate information about the patients is gathered.
3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
4. Patient management plans are developed and carried out.
5. Patients and their families are counseled and educated.
6. Information technology to support patient care decisions and patient education is used.
8. Health care services aimed at preventing health problems or maintaining health are provided.
10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.
12. Evidence from scientific studies related to the patients’ health problems is located, appraised and assimilated.
13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.
15. Information technology to manage information, access on-line medical information and support the healthcare professional’s own education is used.
24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.
Donna M. D’Alessandro, MD
Associate Professor of Pediatrics, Children’s Hospital of Iowa
May 29, 2006