''Lazy eyes'' are kind of eye diseases that occurs in children younger than 9 years old. Its name in medical is amblyopia. It causes two kind of eye problem: a vision deficiency in an eye but the other one is physically normal, or out of proportion to associated structural abnormalities of the eyes. From this we can see that lazy eyes can only happen in children younger 9 years old. It is a developmental problem in the brain, not the problem of eyeball. It can be sort into four types, these are strabismic amblyopia, anisometropic amblyopia, Form-deprivation, and occlusion amblyopia.