Amblyopia, sometimes called lazy eye, occurs when the brain seems to favor one eye at the expense of the other. This leads to impaired vision in the affected eye.

The National Eye Institute mentions these potential causes:

• A condition that interferes with the eye’s ability to focus.
• Poor alignment between the eyes, medically called strabismus.
• Cataract in one eye.
• Nearsightedness, farsightedness or astigmatism in one eye.

Source: HealthDay