Vision Disorders

Nonparalytic strabismus is thought to be due to underdeveloped binocular reflexes within the brain resulting in diplopia, the projection of a double image of a single object to the brain. The brain does not see both images, however—particularly if onset is at a young age and remains untreated—because the visual system develops an adaptive sensory mechanisms to deal with the confusion. This mechanism is called suppression, in which the brain suppresses the image from the weaker eye and neurons associated with the dominant eye take over.

The most common problem associated with suppression is strabismic amblyopia, or lazy eye, which affects more than four million people in the United States and causes blindness in more people under 45 years of age than any other ocular disease and injury combined. If it is present at birth or occurs within the first few months, vision never develops in the affected eye. This is called amblyopia of arrest. When the problem appears during the first two or three years, it is termed suppression amblyopia.