Prenatal Diagnosis for Colorblindness

Colorblindness cannot be screened for using a genetic test. The only effective method for determining whether someone is colorblind is to administer a visual color test. Usually, this test is administered during a physical exam when a child reaches age 4 and has learned how to distinguish between different colors.

• There is no method for prenatal screening of colorblindness.

Eye Development and Colorblindness

• The human eye does not develop to the point to which it can distinguish between colors until the child reaches four months old, when the retinal cones begin to form. The majority of people develop normally, but between 7-10 percent of people cannot distinguish between red and green. A tiny proportion of individuals (about one in 40,000) cannot distinguish any colors at all. More men than women are born colorblind. The condition manifests by either the malformation or lack of formation of the cones in the eye, which allow the brain to perceive differences in color.

Heredity and Colorblindness

• Colorblindness is a hereditary condition. Only a single healthy color perception gene is necessary for a human to be able to perceive color properly. This is carried in the X chromosome, so males (who carry the XY sex chromosomes while females carry the XX sex chromosomes) are more vulnerable to the condition. According to pediatrician Dr. Alan Greene, chief medical officer of health website A.D.A.M, if the mother of the child is a carrier of the colorblindness gene, the male children are 50 percent more likely to contract the condition. Fathers with the condition cannot pass it to their sons, but will give it to their daughters. Their daughters, despite this, will not be colorblind unless their mother also carries the gene for colorblindness, but is not also colorblind.

Determining a Child's Chances of Colorblindness

• Female children are unlikely to develop colorblindness unless their mothers also carry the gene. While genetic tests for colorblindness are not available, prospective parents can determine the rough probability of their children developing the condition by conducting family history research and interviews to determine its presence in their heredity. Females cannot be colorblind unless their father is colorblind, and their mother carries the gene for the condition. Males can be colorblind if only one of their parents carries the gene.

Tests for Colorblindness

• Simply because a child is having trouble learning the difference between the colors at a young age does not necessarily mean he is colorblind. Most children only learn how to match different colors with the appropriate words at the age of 4 or 5 with proper instruction. After they accomplish this, a physician can test for dichromacy (an inability to distinguish between red and green) using a series of specially designed images contrasting the two colors. This is called a Pseudoisochromatic Plate Test, consisting of a series of different-colored dots mixed together.

Vision Aids for the Colorblind

• Vision aids are available to the colorblind to assist them in distinguishing between colors. Monochromatic colorblindness cannot be treated in this fashion, but the far more common red-green colorblindness can be. Specially tinted contact lenses and eyeglasses can be worn to make the colors more distinguishable.