Color blindness- Types, causes and more.

What is colour blindness?

Inability to see colors in a normal way refers to as color blindness, or also color deficiency.  It usually occurs when someone cannot distinguish between certain colors such as greens,reds or blues.

The anatomy of the eye-

Two types of cells detect light in the retina, the rods and cones. Rods detect only light and dark. They are very sensitive to low light levels. However, Cones cells detect color, which are of 3 types.

When one or more of the color cone cells are absent, not working, or detect a different color than normal, color blindness can occur. When all 3 cells are absent, Severe color blindness occurs.

Types of color blindness or deficiency-

Mild color deficiency– people can see colors normally in good light. However they have difficulty in dim light.

Moderate deficiency– cannot distinguish certain colors in any form of light.

Severe deficiency– one sees everything in shades of gray. This is known as achromatopsia.


The symptoms of color blindness or deficiency include:

  • trouble seeing colors
  • trouble seeing brightness of colors
  • inability to tell the difference between shades of colors.

Causes of Color Blindness

  • congenital
  • lack of cones in retina
  • disruption of function of cones in retina
  • trauma
  • toxic effects from drugs
  • metabolic or vascular disease

At risk population-

  • common in men
  • diabetic people
  • macular degeneration
  • glaucoma
  • alzheimers
  • chronic alcohol consumption
  • multiple sclerosis

Test to diagnose color deficiency-

The test consists of showing you a pattern made up of multi-colored dots. If you do not have a color deficiency, you will be able to see numbers and shapes. However  If you are color blind, You may not see anything in the pattern at all.

Types of inherited color blindness-

color blindness- vcurehealthcare

Normal vision uses all 3 cones correctly and can hence differentiate between all colors, they are known as trichomats.

There are several types of inherited color deficiency which include-

Anomalous Trichromacy

People with ‘faulty’ trichromatics are referred as anomalous trichomacy. In these peple one type of cone perceives light slightly out of alignment,thus leading to faulty interpretation. It has 3 types-

Protanomaly– this refers to as reduced sensitivity to red light

deuteranomaly this refers to sensitivity to green light. It is the most common form of colour blindness

tritanomaly – it is a reduced sensitivity to blue light. It is extremely rare.

People with deuteranomaly and protanomaly are collectively known as red-green colour blind people.


People with dichromatic colour vision have only two types of cones. Thus there is a total absence of function of one cone.

Protanopia- people are unable to perceive ‘red’ light

Deuteranopia- unable to perceive ‘green’ light

Tritanopia- unable to perceive ‘blue’ light.


People with monochromatic vision can see no colour and only different shades of grey. It is rare.

It is best to consult your ophthalmologist at the earliest, if you or your children, face the slightest difficulty in perception of colour.

Also read-

Leave a Reply