Why Men Are More Likely To Be Colorblind

6

Color vision deficiency (CVD), commonly called colorblindness, is much more common in males than females. Inherited colorblindness affects 1 in 12 men and 1 in 200 women, but many people don't know why there's such a significant difference.

Dhruv Sethi, M.D., an ophthalmology resident at Henry Ford Health, explains why more men have CVD and the role of genetics in this condition.

What Is Colorblindness?

While many people use the term "colorblindness," it doesn't accurately describe CVD. "Inherited CVD doesn't cause vision loss," says Dr. Sethi. "People with this condition just see colors differently than those with normal color vision."

CVD occurs when cells inside your retina, known as cones, don't work correctly. "Your cone cells perceive either red, green or blue light," says Dr. Sethi. "People with color vision deficiency have a difference in one or more types of cone cells."

For example, the most common type of color vision deficiency is deuteranomaly. This type is a difference in the cone cells that perceive green.

"Color vision deficiency ranges from mild to severe," says Dr. Sethi. "Some people with deuteranomaly may perceive most shades of green, others may not see greens at all, and many people are somewhere in the middle."

How Colorblindness Runs In Families

Most cases of CVD are caused by a genetic mutation that affects the cone cells in the eye. The gene that causes CVD is on the X chromosome, and it's a recessive trait.

Recessive traits typically mean you must inherit the genetic mutation from both parents to have the condition. But here's why males get CVD more: Females have two X chromosomes (XX), but males only have one (XY).

"Females may inherit one normal X chromosome from their father and one with the CVD variant from their mother, or vice versa," explains Dr. Sethi. "If this happens, the X chromosome with normal color vision can override the CVD chromosome. The daughter will not have CVD, but she will be a carrier. Carriers can pass the condition on to their biological children but won't have any signs of the condition."

Some women can and do get CVD, however, if:

• Both parents have CVD
• The father has CVD and the mother is a carrier

Males only have one X chromosome, so they can't override the gene variant. "Males can get the CVD gene variant from just one parent," says Dr. Sethi. "And statistically, the chances of one parent having the gene variant is greater than the chances of both parents having it."

And does colorblindness really "skip a generation"? This is a common misconception, says Dr. Sethi.

"People think CVD skips a generation because a daughter can inherit the gene from her father and become a carrier," says Dr. Sethi. "Then, the daughter can pass CVD on to her son. It looks like the CVD gene skipped the daughter, but it didn't. She still has the gene-she just has no symptoms of CVD."

When Genes Aren't the Cause Of Color Blindness

Most people with CVD have the inherited type, so they've had it since birth. But a different kind of CVD, known as acquired CVD, isn't caused by genetics and affects people later in life.

"Acquired color vision deficiency can occur if a disease affects your retina or changes how your brain processes colors," says Dr. Sethi. "Some of these conditions can be serious, so contact your provider immediately if you notice a change in your color vision."

Possible causes of acquired colorblindness include:

• Age-related macular degeneration (AMD)
• Alzheimer's disease
• Cataracts
• Diabetes
• Glaucoma
• Medications
• Nutritional deficiencies
• Parkinson's disease
• Retinal detachment
• Sickle cell disease
• Tumors in the brain or eye

Partner With Your Provider For Healthy Eyes

Inherited CVD isn't a health problem-it's just a variation of normal vision. "You can live a full, healthy life with genetic color vision deficiency," says Dr. Sethi. "Most people adapt very well to seeing the world differently."

Whether you have inherited CVD or normal color vision, proper eye care is essential. Keep your eyes healthy by regularly seeing your eye care provider for a comprehensive eye exam.

"During an eye exam, we screen for common eye problems, including diseases that can cause blindness," says Dr. Sethi. "We often catch these problems early, when treatment is more successful. Screenings are the best way to ensure you have healthy vision for life."

Reviewed by Dr. Dhruv Sethi, an opthamology resident at Henry Ford Health.

Categories : FeelWell

Tags : Ophthalmology, Dhruv Sethi