Imagine the challenges a driver unable to see any color would face when trying to obey traffic signals. A police officer that can not describe what a suspect was wearing when last seen would have significant difficulties. Color blindness and color vision deficiencies can affect everything you do from something as simple as choosing what to wear to critical skills that your job might require, such as differentiating colored wires in an electrical circuit. Getting a proper diagnosis can help you understand what type of color vision problem you have, which makes seeking treatment much easier.
How do you see in color?
The eye has a color spectrum of about seven million colors. Our eyes contain three types of cells or “cones” that contain photo pigments that enable us to see color. Within a small pit close to the optic nerve are approximately six to seven million photoreceptors or cones of three types: S-cones, M-cones, and L-cones, with the letters standing for short, medium, and long-wavelength light. Wavelengths of reflected lights control the colors the eyes see. All three light cones generate the colors of red, green, blue, and the various hues thereof. A person with normal color vision has and uses three light cones. Any damage to or absence of the cones results in color blindness or a color vision deficiency.
- Color Blindness occurs when your photo pigments are so abnormal that you cannot detect any color, so everything appears gray. Total color blindness is very rare.
- A Color vision deficiency occurs when your photo pigments are abnormal and cause your color perception to be limited. For instance, you may be unable to detect red or green or both red and green, or you may b unable to detect blue or yellow or blue and yellow, etc.
Types of Color Vision Deficiencies
Monochromacy is a very rare condition, which is “actual color blindness,” where a person sees only one or no color. It occurs when a person has only one or no photo pigments in their cones.
Dichromacy is an eye condition, which results in a person seeing only two of the three colors. It occurs when a person only two of the photo pigments in their cones or two of the three cones are damaged in some way.
Tritan Vision is a very rare form of color vision deficit, often known as “blue-yellow color blindness” because it affects the blue cone photo pigments in your eye. Tritan vision can be congenital or can develop as a result of an illness or injury. There are two types of Tritan color vision deficiency:
- Tritanopia is a form of color blindness that results in a person seeing blues as green and yellow as shades or violet or gray. Reds appear pink. It occurs when short-wavelength cones in the eye or “S-cones” are missing.
- Tritanomaly is a form of color blindness that results in a person seeing blues as greener and yellow and reds as shades of pink. It occurs when the functionality of the “S-cones” are limited.
Protan Vision is the most common color vision deficit, often known as “red-green color blindness,” because it affects the red cone photo pigments in the eye. Protan vision is an inherited vision defect.
There are two types of Protan color vision deficiencies:
- Protanopia is a form of color blindness, referred to as “red blind,” where the person is not able to distinguish colors with hues of red such as red, orange, pink, violet, or purple. Red appears as black. Orange and Green appear as yellow. It occurs when the long-wavelength cones or “L-cones” are missing.
- Protanomaly is a form of color blindness, referred to as “red weak,” that results in a person seeing any shade of red, yellow, or orange as having a greenish hue to it. It occurs when the functionality of the “L-cones” are defective.
Deutan Vision is a common color vision deficit, often known as “red-green color blindness,” because it affects the green cone photo pigments in the eye. Deutan is an inherited vision defect.
There are two types of Deutan color vision deficiencies:
- Deuteranopia is a form of color blindness, referred to as “green blind,” where the person is unable to see the color green. Green can appear beige, and red can appear brown or yellow. It occurs when the green cone cells do not function.
- Deuteranomaly is a form of color blindness, referred to as “green weak,” where the person sees a distorted version of yellow and green, which appear redder. It occurs when the functioning of the green cone cells is limited.
Causes of Color Blindness or color vision deficits
Color blindness is both a genetic and acquired condition. With the genetic form, there is variation in how the cones respond to specific wavelengths. Acquired color blindness can develop due to eye diseases such as cataracts, glaucoma, and macular degeneration. It can also be due to acute retina damage, illness, or aging.
Common Eye Diseases
Cataracts develop in the eye’s lens. As the lens ages, it becomes dry, stiff, and loses the ability to focus. Loss of clarity in the lens can severely impact vision. Symptoms of cataracts include cloudy, blurred, or double vision in a single eye, poor night vision, and sensitivity to light. Not smoking, limiting alcohol, controlling blood pressure and blood sugar, and wearing sunglasses outdoors may lower the risk of developing cataracts. Surgery is available should they develop.
Glaucoma is not one disease. It is group of eye diseases that gradually cause damage to the optic nerve and can ultimately result in vision loss. Open-angle glaucoma is the most common type of glaucoma. It occurs when the pressure in the inner eye gradually increases because eye fluid becomes clogged inside of the eye’s drainage canals. Another form of glaucoma is angle-closure glaucoma, which is a sudden rise in eye pressure caused by the iris bunching up over the drainage canals and preventing the canal from draining.
- Age-Related Macular Degeneration
The leading cause of blindness in seniors over 65 is age-related macular degeneration. This disease develops as macular tissues in the rear of the eye begin to thin. People who are more at risk are those who smoke, are obese, and have significant light exposure. In some people, doctors can slow age-related macular degeneration. The condition has various types, and doctors will perform diagnostic tests to determine which treatment is best.
How is Color Blindness or color vision deficiency diagnosed?
Pseudoisochromatic plate tests are frequently used to test color vision.
Three types of tests are used to diagnose color vision deficiency:
- Pseudoisochromatic plate tests
This plate test is the most common test for color blindness. An eye doctor will have you look at images made up of colored dots with differently colored numbers or shapes in the middle of the image. If you can’t see the number or shape, you may have a type of color blindness or a color vision deficiency.
- Hardy-Rand-Rittler (HRR) HRR shows colored numbers against a colored background of dots. The test supports very efficient color deficiency screening. The first four plates are used to show the patient how the test works. The fourth plate has no figure and serves to uncover attempts to memorize this test. The next six plates (screening series) present the most difficult protan, deutan and tritan (red, green, yellow, and blue) targets. Success with these plates defines the subject as having ‘normal color vision’ and completes the test. The subsequent 14 plates are the diagnostic series and provide diagnostic as to the extent (mild, medium, or strong) and type of defect (Protan, Deutan, Tritan).
- The Ishihara Test is a widely used screening test for color blindness. It contains a several colored plates, known as Ishihara plates. All of the plates include a circle of dots appearing in random order of color, brightness, and size. The colored dots are arranged in such a fashion that a person with normal color vision will see a single-digit or two-digit number within the array of dots. But a color-blind person will either be unable to see a number or will view a different number than the one seen by a person with normal color vision.
Most people will view the images differently. Those people with certain types of color blindness will see different numbers from those not affected by color blindness. Ishihara tests are similar to HRR, but they test for red-green defects. The Ishihara colorblind test is made up of colored plates, which mainly test red-green color defects.
- Hue test
In a hue test, a person will get disks that are of different types of colors. The eye doctor will have that person arrange them in order of hue, such as from red all the way to purple. If the person can’t put them in the correct order, they may have a type of color vision deficiency. An eye doctor will use this test for people who need to have a very accurate color vision for their jobs — like photographers or designers.
- Farnsworth-Munsell 100-hue disk matching. The test consists of 4 trays of colored disks in varying hues with a reference disc at the end. The person being tested arranges the disks within the tray in a line of gradually changing hue. The closer the match is between the test subject’s results and the correct results, the more normal the person’s color perception is.
The Farnsworth-Munsell tests the chromatic discrimination between 100 different hues. The Farnsworth Munsell test is used to determine whether a person is colorblind. It also reveals the severity of the colorblindness, and whether the color blindness is congenital or not.
- Farnsworth D-15 is a color blindness screening test with 15 disks in different hues. It is an abbreviated version of the Farnsworth Munsell 100-hue disk test.
- Lanthony Desaturated D-15 consists of 15 disks in paler hues than the Farnsworth D-15 that the test subject arranges by hue intensity. The test is used to identify fine-color congenital and acquired color deficiencies.
- Anomaloscope test
An anomaloscope is an Instrument used to test for color blindness and quality and quantity of color anomalies such as red-green or blue-yellow. This test will check whether you can match the brightness of two shades of light. You will look into an eyepiece at a circle. The top half of the ring is a yellow light. The bottom half of the ring is red and green lights. You use knobs to adjust the lights and try to get them to match in color and brightness.
There are more sophisticated tests that are widely used to ascertain whether someone with a color vision deficiency would be suitable for specific occupations.
A Lantern test is one such test that is used to identify people not suitable to work as train drivers or in marine and aviation jobs or other occupations where the work requires the ability to accurately reading the colors of lights for safety reasons.
Why test for color blindness?
Color vision deficiencies can be mild, moderate, or severe. An accurately calibrated test can distinguish between different levels of severity, which can affect your career choice.
Individuals with mild color vision deficiencies might make a few mistakes on a color vision test. Their color vision deficiency will not likely cause difficulties, even on color-related tasks. Unless a job requires perfect color vision, the majority of career choices are open to people with a mild color vision deficiency.
Those people identified with a moderate color vision deficiency consistently make mistakes on a color vision test. Their ability to discriminate colors is impaired to the point that it may cause difficulty in school or at work when the task involves color. Careers that require perfect color vision may present significant and possibly insurmountable obstacles for such individuals.
Even though they can differentiate some colors, people with a severe color vision defect have difficulty distinguishing between colors. Those people with a severe color vision deficiency will likely experience difficulty with schoolwork and any other work that involves color-related tasks. These individuals may not qualify for any job that has a color vision requirement.
Dr. Thomas Azman has been treating people who suffer from red-green color blindness since 1975, and since 1999 with his proprietary ColorCorrection System™. The system can change the wavelength of each color going into one or both eyes using eyeglasses or soft contact lenses. With an astonishing 100 percent success rate, Dr. Azman has helped people with colorblindness all over the world to pass many types of pseudoisochromatic plate tests.
Aren’t you ready to see the world in color? Contact us for treatment by calling (443) 470-9844, or filling out our contact form.