why eating carrots is important for good vision?

Answer 1

Because of the beta carotene.

Answer 2

They are high in Vitamin A, which helps eyesight.

See
http://www.allaboutvision.com/nutrition/vitamin_a.htm

Answer 3

Eating carrots only improves eyesight if a person has a Vitamin A deficiency. Most people in the developed world have sufficient Vitamin A, so eating carrots doesn't help their vision.

http://www.snopes.com/food/ingredient/carrots.asp

http://healthlibrary.epnet.com/GetContent.aspx?token=0d429707-b7e1-4147-9947-abca6797a602&chunkiid=156972

http://www.webmd.com/diet/carrots-good-for-eyes