Amblyopia is the lack of development of vision in one eye that is not directly caused by any eye health problem. It is not correctable with lenses alone. Amblyopia occurs before the age of six and it is estimated that 2-4% of children under the age of six have amblyopia.

Amblyopia results from a large difference in the prescription between the two eyes or it can occur when strabismus (crossed eyes) is present. It can also occur when something is interfering with the clarity of the various components of the eye. This causes blurred vision in the affected eye. Because the image that is sent to the brain from the affected eye is poor, the brain will ignore this eye. As the brain ignores the eye over time, very few connections are made between the brain and the eye. It is this lack of connections between the brain and the eye that causes the eye to become amblyopic. This is why lenses alone cannot correct the problem.

Amblyopia occurs when one eye experiences a blurred view and the other a normal view, but the brain only processes the normal view.

Most of the time there are no symptoms of amblyopia. Since only one eye is affected, the other eye usually has reasonably good vision and tends to take over all visual tasks.