Color Blindness Types

For the average human, a healthy eye includes a retina made up of lots of rods and cones.  The rods are sensitive to light, and are more dense around the edges of the retina – hence why you may have noticed your peripheral vision is able to pick up light easier at night (such as stars, or a police camera van). There are three types of cones, one type for short wavelength light, one for medium, and one for long. Each color you see is a reflection of light at a certain wavelength. 

Understanding that makes it easy to understand how color blindness works, and where the types of color blindness originate. The less cones of a particular type on someones retina, the less sensitive they are to the associated wavelengths (colors). These deficiencies manifest in 3 main Categories, and are explained below the example color blindness simulation, which makes for a good reference. 

Color Blindness Variations

No color blindness, red green color blindness, blue yellow color blindness, total color blindness

Red Green Color Blindness Types

  • Protanomaly is caused by defective L-cones, lowering sensitivity to red hues.
  • Protanopia is caused by absent L-Cones, removing the ability to see reds – a severe form of color blindness.
  • Deuteranomaly is  caused by defective M-cones, weakening the ability to differentiate red and green hues in as much as 5% of all males.
  • Deuteranopia is caused by absent M-cones, giving a moderate inability to discriminate red – green hues.

By far the most common form of color blindness is Deuteranomoly. If you suffer, chances are you can’t even tell the first 2-3 slides in the above simulation are even different (I cant tell). Don’t forget to take a color blindness test if you never have! 

All four of the above defects are hereditary and passed on through genetic inheritance. Not all sufferers suffer at the same intensity. For some these forms of color blindness can be so mild the person can go their entire life and never find out they were color blind in the first place. For the less fortunate who inherit Protanopia or Deuteranopia, life can be somewhat more frustrating, especially in the case of protanopia where some dangers become very real, with a prime example being the inability to differentiate the color of traffic lights. 

Blue Yellow Color Blindness Types

  • Tritanomaly is caused by weakened S-cones, reducing the ability to distinguish some blue and yellow hues.
  • Tritanopia is extremely rare, resulting from a total absence of S-cones. Removing the ability to distinguish some blues with green, and some yellows with violet.

Blue yellow color blindness is very rare, and in fact quite misleading. Color confusion for sufferers will actually revolve around blues to greens, and yellows to violets, rather than direct confusion between blue and yellow. There is no specific prominence for Blue yellow color blindness in males as the chromosome that can cause this defect genetically is located on chromosome 7, rather than X. 

Sources generally confirm that only 0.01% of humans suffer from this defect, and a higher portion of those that do actually inherit it after birth through non genetic means such as trauma to the eye through impact, light/UV, or miss-treatment as a baby. Alcohol and some organic solvents have also been linked to higher proportions of blue yellow colorblindness. 

Total Color Blindness Types

  • Rod monochromacy is a rare, non progressive inability to distinguish any color, resulting from non functioning or absent retinal cones. Rod monochromacy is typically associated with sensitivity to light (Photophobia) and poor vision.
  • Cone monochromacy is also a rare, total color blindness, however is accompanied by relatively normal vision.

These conditions are color blindness at its most severe, though rod monochromacy is arguably worse as the condition’s interference with healthy vision often extends beyond color differentiation to include other conditions including: 

  • Completely unable to distinguish colors.
  • Amblyopia (reduced visual acuity)
  • Hemeralopia (with the subject exhibiting photophobia – severe light sensitivity)
  • Nystagmus: Involuntary eye movements
  • Iris operating abnormalities

Fortunately this is extremely rare and thought to be present in less than 0.003% of men and women, with no predisposition toward either sex. 

Cone monochromacy is less severe, but with only a few cases ever officially documented, even more rare. Naturally, this comes in 3 formats: Blue (S-Cone), Green (M-Cone), and Red (L-Cone) monochromacy. 

It was a long held belief that  dogs and other mammals had monochromatic vision, but modern science has long since determined it more likely that dogs, and most other mammals are actually only red-green colorblind, and indeed have Dichromatic color vision. Studying the surface of the retina is the only relatively sure way of determining this, since most dogs don’t speak English (yet). 

Further Reading: