Color Blindness

Color blindness is a general name used for partial or complete inability to see certain colors.

This disease is called Daltonism. Luminous energy entering into the eye, our visual organ, focuses on the retina with the help of the lens. Cells in the retina are sensitive to certain wavelengths of luminous energy. These receptors are analyzed in two main categories. The receptors responsible for night vision and adaptation to darkness are called “basil”, and the ones responsible for light vision and visual sharpness are called “cone”. 

Figure 1.  Example of an Ishihara color test plate.

Cone receptors are divided into 3 categories and perceive three primary colors: red, blue, and green. Since the luminous wavelength range by which each receptor is affected is quite wide, luminous wavelengths coming into our eyes generally stimulate more than one cone receptor. With the mixture of these three colors, we become able to recognize different colors. If a person has only two cone cells for recognizing colors, s/he can only see these two colors and their mixture. For instance, if the cone cell recognizing the color red does not exist, only the red color cannot be recognized. The colors that can be seen by this person are blue and green and their mixtures. The same applies to the absence  of green or yellow cone cells. In cases where only one color cone exists and two color cones do not exist, e.g. only the blue color cone is present while red and green color cones do not exist, the person cannot recognize the colors red and green. This kind of color blindness is called “red-green blindness”. This is the most common color blindness type. Anopia is the name given for the case where none of the each color cones are present. In this case, the person, who is entirely color-blind, only sees black and white. Color perception disorders are quite common. 1 out of 12 men experience this disease, while it is rare in women.

Although the disease is mostly genetic, it may develop later due to eye, optic nerve or brain damage and exposure to some chemicals. Some medications may also cause deterioration in vision. Since it is a genetic disease, families with such problems should be given genetic counseling. If mothers are carriers, their children may become color-blind even though they themselves are not. When color-blind youngsters choose an occupation, they should choose one that will not be affected by this disease. For example, a color-blind person should not work in the design or textile sector where recognizing colors is important.

Patients do not understand by themselves that they are color-blind. Patients may have a visual ability close to normal or, in advanced cases, an ability that can cause confusion, depending on the deficiency level of the pigments. In very rare cases, patients can only recognize black, white, and tones of gray.

Figure 2. Color perception demonstration of an healthy (left) individual and a patient diagnosed with dyschromatopsia (right).

There are many different tests in color-blindness examinations. The most commonly used among them is Ishihara, where patients are made to read a book consisting of letters made of colorful dots. Special colorful beads are also used for examination.

Since most of the cases are genetic, there is no permanent treatment for such color-blindness.  One-color contact lenses produced in a special intensity and color tone help patients perceive colors in an accurate way. A significant increase in color-vision can be detected in most patients using such lenses. On the other hand, color-vision problems in patients exposed to medications and chemicals can be solved with the required interventions.