If a child who is perhaps barely four years old, asks you this question, as you both sit in the eye doctor's waiting room, as you look with love at green eyes fringed with long lashes that when shopping women notice and shake their heads saying, "such a shame to waste long eyelashes on a boy," you politely ignore them.
You do not use large words like pediatric strabismus or blame it on genetics or heredity.
You tell the child who is perhaps barely four, that Mommy and Daddy both wear glasses, then you help them name every other person the child knows who wears glasses. You explain, "People wear glasses so they can see clearly all of the things they like to look at."
The child smiles, trusting you, and says, "like birds and fire trucks and horses and pictures in books?"
"Yes," you answer, hoping there will be no need for surgery and that it was caught in time so this green-eyed boy does not grow up almost legally blind, like two grandparents.