An estimated 1% to 5% of children worldwide have lazy eye— a childhood condition where the vision does not develop properly. It happens because one or both eyes are unable to build a strong link to the brain. It usually only affects one eye, and means that the child can see less clearly out of the affected eye and relies more on the “good” eye. This condition responds well to treatment if begun early on. However, by age 7, if the lazy eye is undiagnosed or left untreated, it can cause permanent visual damage, impair daily activities such as reading, walking or driving safely, and lead to social and financial deficits later on in life.