An inherited disorder that affects men more than women is colour blindness. It is simply the inability to differentiate colours. It is very rare to be totally colour blind. The capacity of colour vision is located on X chromosome. Men have only one X chromosome compared to women who have two X chromosome and the probability of inheriting at least one X with proper colour vision is high in women. Hence it is more prevalent among men.
The retina of our eye contains light sensitive cells called rods and cones. Rods give us the night vision and cones are responsible for perceiving colors. Cones contain colour-responsive chemicals called cone pigments. There are three kinds of colour-sensitive pigments - Red-sensitive pigment, Green-sensitive pigment, Blue-sensitive pigment. Each cone cell has one of these colours so that it is that colour-sensitive.
The most common type of colour blindness is red-green colour blindness. It occurs when either red or green cones are not present or they are not functioning properly. Normal color vision uses all three types of light cones correctly and is known as trichromacy. People with normal colour vision are known as trichromats. People with dichromatic color vision have only two types of cones which are able to perceive color i.e. they have a total absence of function of one cone type. People suffering from protanopia are unable to perceive any ‘red’ light, those with deuteranopia are unable to perceive ‘green’ light and those with tritanopia are unable to perceive ‘blue’ light.