Protanopia is a form of colour blindness in which a person's eyes are unable to receive the red light part of the colour spectrum. If a person can still see some red light then it is considered only a weakness known as Protanomaly.
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How does this happen?
In order to view colour the eye has special receptors called rods and cones. As we can see in this diagram, when a person has Protanopia they are lacking the long-wavelength sensitive retinal cones (L-cones). The brightness of red, orange, and yellow is much reduced. Colours become more brown or blue and red and green or blue and green blend into each other and become difficult to discern between. It is similar to Deuteranopia but there is an abnormal darkening of red area so that it appears almost black. A person with normal vision can distinguish 7 hues while a person who has Protanopia may only be able to distinguish 2 or 3 hues.
Who can have Protanopia?
Protanopia is a sex -linked, congenital color vision deficiencies condition meaning that it is hereditary. It is passed on through the X-chromosome. Since men only have one X -chromosome they are more likely to be colour blind. Females have 2 X-chromosome and are therefore only a carrier and as long as only one X is affected they will exhibit no signs of colour blindness. About 2% of males have Protanopia or a form of Protanomaly and for females it is about 0.02%.
What are the colour-related hazards?
While less colour blind people have Protanopia it is more hazardous than Deuteranopia. This is because of the range of colour they are seeing and a lack of red perception when it comes to a red stop light. In many countries those who are colour blind are not able to receive a driver's licence.