Amblyopia, commonly known as a "lazy eye", is a reduction in vision in one or both eyes due to abnormal visual development as the brain learns how to interpret images from the eyes. It occurs during early childhood if the eyes do not work together properly or receive different images. Treatment involves patching the strong eye to force use of the weak eye, improving focus with glasses, or in rare cases surgery. Early diagnosis before age 5 and treatment increases the chances of fully correcting vision.