Experiments in animal models revealed that unilateral lidclosure, artificial esotropia or anisometropia cause amblyopia comparable to that occuring in humans and produces morphological and functional anomalies in the visual centers. Form vision deprivation and abnormal binocular interaction have been identified as amblyopiogenic factors. The age of susceptibility for amblyopia in humams needs better definition. Uncontrolled occlusion in infants must be avoided and congenital or traumatic cataracts occuring in infancy should be operated upon as early as possible and the aphakic eye(s) optically corrected without delay to prevent deprivation amblyopia.