As an optometrist, I always get many people asking me what is color vision deficiency? Well, color vision deficiency is a condition that deprives an individual the ability to distinguish certain color shades. In some severe cases, the patient might not be able to see colors at all.
Many people refer to this condition as color blindness. However, I have only had very few patients who are completely colorblind. People suffering from color vision deficiency are able to see colors; the problem is that they have difficulty differentiating between blues and yellows or specific shades of greens and reds. For those who are completely colorblind, all things they see look black, white or grey. Although a color deficiency will not inhibit your ability to see or function, it may determine which jobs you are less suited to perform. Most color deficient individuals are not painters, electricians or pilots.
What is the cause of color vision deficiency?
Although injury and certain diseases can cause color vision deficiency, it is mainly an inherited condition. It is commonly passed from mother to son through an X-linked recessive gene. Some of the diseases that might lead to color vision deficiency include: leukemia, diabetes, Parkinson’s disease, multiple sclerosis, sickle cell anemia, Alzheimer’s disease, macular degeneration and glaucoma. Other causes include aging, exposure to certain chemicals and some types of medications.
How is color vision deficiency inherited?
Once I diagnose a patient with color vision deficiency, I always ask them whether anyone in their family suffers from this condition. This is because most cases of color vision deficiency are usually inherited. Some of you might be wondering how this condition can be inherited. Well, it all goes back to the genetic makeup of human beings.
The red-green and blue cone monochromacy color vision defects are inherited from the X-linked recessive gene. Mutations in OPNILW and OPNIMW genes which are contained in the X chromosome are what cause color vision deficiency.
Red-green color vision defects occur in the event of genetic changes in the OPNILW and OPNIMW genes. This leads to the production of abnormal opsin pigments or an absence of M or L cones thus affecting red-green vision. These changes also lead to the production of premature or defective S cones. Impaired S cones alter the perception of the blue color and make it difficult for a person to differentiate between dark blue and black or shades of blue and green.
Blue cone monochromacy occurs when the genetic changes in OPNILW and OPNIMW genes prevent the normal functioning of L and M cones. Only the S cones function normally. The result is poor color vision and reduced visual acuity.
Why are men more prone to color vision deficiency than women?
As I had explained earlier, color vision defects are inherited through the X-linked recessive pattern. The X chromosome is one of the two sex chromosomes in human beings. Males have only one X chromosome therefore, it only takes one genetic change in each cell to cause color vision defects. Females have two X chromosomes therefore, for them to get a color vision defect, a genetic change should occur on both chromosomes. Color vision defects are usually passed on from mother to son. Fathers cannot pass on this condition to their sons since they cannot pass their X-linked traits.