COLOUR- BLINDNESS ::::
This is a defect of retina in which a person cannot see one or more colours Some persons are completely colour-blind and see everything in black and white only Some are partially colour -blind not seeing particular colours In males -8.0% and in female about 0.5% are partially or totally colour blind The defect lies often in the cones of the retina sometimes it may be in the brain also
NIGHT BLINDNESS :::
When it is not possible to see in dimlight due to reduced power of dark adaptation the condition is called night blindness It can be hereditary retinitis pigmentosa vitamin Adeficiency disease or pathological condition It has been found that there is relationship between vitamin A and rhodopsin formation it has photochemical properties and it stimulates rods The deficiency of vitamin A affects rhodopsin formation and results in night blindness
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