Amblyopia, also known as lazy eye, is a condition in which vision in one eye is very much worse than in the other. The two 'views' provided by the eyes cannot be combined into one '3-D' image by the brain, so the the brain learns to dull or ignore the image of one (usually the worst eye) patient loses their 'binocular' vision (binocular vision is where the combination of the images from the two eyes enables the person to see in 3-D).