Color Blindness

Colour Blindness

Colour blindness is a genetic disorder which occurs when the patient is unable to see colours in a normal way. It is also known as colour deficiency. Colour blindness often happens when someone cannot distinguish between certain colors. This usually happens between greens and reds, and occasionally blues.

In the retina, there are two types of cells that detect light. They are called rods and cones. Rods detect only light and dark and are very sensitive to low light levels. Cone cells detect colour and are concentrated near the center of the vision.

Colour blindness can happen when one or more of the color cone cells are absent, not working, or detect a different colour than normal. Severe colour blindness occurs when all three cone cells are absent. Mild colour blindness happens when all three cone cells are present but one cone cell does not work right. It detects a different colour than normal.

There are different degrees of colour blindness. Some people with mild colour deficiencies can see colours normally in good light but have difficulty in dim light. Others cannot distinguish certain colours in any light. The most severe form of colour blindness, in which everything is seen in shades of gray, is uncommon. Colour blindness usually affects both eyes equally and remains stable throughout life.

Types of Color Blindness

• Trichromacy - Normal colour vision uses all three types of light cones correctly and is known as trichromacy. People with normal colour vision are known as trichromats.
• Anomalous Trichromacy - People with ‘faulty’ trichromatic vision will be colour blind to some extent and are known as anomalous trichromats.
• Protanomaly - This is a reduced sensitivity to red light.
• Deuteranomaly - This is a reduced sensitivity to green light and is the most common form of color blindness.
• Tritanomaly - This is a reduced sensitivity to blue light and is extremely rare.