What is color blindness?

Color blindness, otherwise known as color vision deficiency, is the inability to differentiate between colors.

There are two types of cells in the retina that detect light: rods and cones. Rods detect light and dark, while cones detect color. The brain uses three color cones – red, green, and blue – to perceive color. If one or more of the cones malfunction or are absent, it results in a form of color blindness.

People with color blindness most commonly cannot distinguish certain shades of red and green, while a smaller percentage find it difficult to determine blue and yellow. Rarest of all is the inability to perceive any color whatsoever, a condition called achromatopsia. Those with achromatopsia only see in black, white, and shades of gray. Color blindness is a spectrum and ranges from mild to severe, and can be accompanied by other vision problems. For instance, achromatopsia is often associated with amblyopia, nystagmus, light sensitivity, and poor vision.

How is color blindness tested?

Envision’s comprehensive eye exam includes color testing to determine if a patient is color blind – if the patient cannot correctly identify a shape or number made up of multicolored dots among other multi-colored dots, or has a hard time identifying any distinguishing pattern in the images, he is color blind.

Plate 1

Those with normal color vision should read the number 74.

Plate 2

Those with normal color vision should read the number 6.

Plate 3

Those with normal color vision should read the number 29. Those with red-green deficiencies read the number 70. Those with total color-blindness can not read any number.

Plate 4

Those with normal color vision should not be able to read any number. Most of those with red-green deficiencies should read the number 5. Those with total color -blindness can not read any number.


Who’s at risk for color blindness?

Males of North European descent are at the greatest risk of being born with color blindness. An estimated 1 in 10 men have a color vision deficiency. Additionally, those with glaucoma, macular degeneration, Parkinson’s disease, Alzheimer’s disease, leukemia, sickle cell anemia, and chronic alcoholism face a greater risk of acquired color blindness. Trauma and toxic effects from drugs can also result in color blindness.

Is there a cure?

There’s no way to treat congenital color blindness; that is, if someone is born with color blindness he will be color blind for the remainder of his life, although certain glasses and contact lenses may be able to help color blind individuals differentiate between similar colors. Acquired color blindness, on the other hand, may be treated by addressing underlying conditions that could have caused the deficiency.