The eye is a magnificent organ; our eyesight depends on the physiology and perception of the eye and the interpretation of the brain. We are able to see because the retina, the membrane at the rear of the eye, contains light wavelength neurorecptors, called rods and cones. Rod cells work in lesser light situations, such as at twilight, and cone cells pick up color and function best in daylight, or brighter light situations. The rods are located around the periphery of the retina, while the cones are focused in the center of the retina. This area where the cones are located is a yellow area in the center of the retina, and in medical terminology it is called the macula.
It is a misconception that when one is color blind they only see in shades of black, brown and white. The rods and cones are genetically programmed to receive certain wavelengths of light. Each color on the spectrum has a different wavelength. Visible light ranges from 400 to 700 nanometers on the electromagnetic spectrum. Light we can see is just a small portion of the complete spectrum that consists of gamma rays, X-rays, ultraviolet, followed by visible light, then infrared radiation, and radio waves.
People that have normal (trachromac) cone cells have specific cones sensitive to the wavelengths of the colors red, green and blue. The colors of the visible spectrum are received by the three types of cone cells and interpreted by the brain. If the genetic coding isn’t quite right in the cone cells the receptors will not be as sensitive. The colors may not be as vivid, or there may be colors not visible at all.
An Anamylous trachromasy refers to color blindness in which the cone cells in the retina that are less sensitive to the colors red, green and blue. An anomalous trachromasy is subdivided into three categories: protanomaly, deuteranomaly, and tritanomaly. The first anomaly, protanomaly, refers to rods that are less sensitive to red, and deuteranomaly refers to rod cells that are less sensitive to green. Dark green may look black. The intensity of the colors seen by people with anomalous trachromasy may see red as black, and green as black. People with anomalous trachromasy are less likely to be able to distinguish different colors. Tritanomaly is different from the previous two types of color blindness. Tritanomaly is a type of color blindness that mistakes the color blue for green.
If you have protanomaly you may see the color spectrum as varying shades of browns, ambers, and blues, and if you have deuteranomaly you may see the color spectrum as varying shades of ambers, yellows, and blues. Finally, if you have tritanomaly you may see the color spectrum in varying shades of pinks, blues and maroon.
Monochromacy: Total color blindness
Monochromacy is the inability to distinguish any colors. This type of color blindness is divided into two categories, which are rod Monochromacy, and cone Monochromacy. Rod Monochromacy is also known as achromatopsia. This condition is characterized by the retina having only rod cells and no cone cells. Cone Monochromacy is characterized by the retina having both rods and cones, but only one kind of cone cells, instead of three.
If you have rod monochromacy, you will not be able to distinguish any colors. You will just see varying shades of gray. If you have con monochromacy, you may be able to distinguish red, blue or green – depending on the one type of cone cells you have. Cones are not color specific, but wavelength specific. The three different types of cones are short wavelength, medium wavelength, and long wavelength specific. Your brain interprets these wavelengths into colors. With rod monochromacy, you may be able to see varying hues of reds, blues or greens in the light of day, or in artificial light, but when it begins to get darker you won’t be able to distinguish any color at all.
In summary, we have two different types of receptors located in and around the retinas of our eyes. The rods are designed to function in low light situations, and the cone cells, which are made up of three different types. Each type of cone has a specific pigment that absorbs light from a specific wavelength. The signals from the information gathered from the rods and the cones are then channeled to the brain to be interpreted. Because of the way our eyes are designed, if they are functioning normally, we can see all the beautiful colors of a rainbow; however, if for some reason, there is an anomaly of some sort your perception of color will be quite different from someone with no impairment. For more information about color blindness refer to my sources.