New knowledge of the pathophysiology of amblyopia has evolved through animal research over the past 30 years. We now know that development and treatment of amblyopia have a critical and sensitive period. After more than a millennium, patching of the dominant eye remains the cornerstone of amblyopia treatment, and compliance plays an important role in its effectiveness. Compliance can now be measured objectively with an occlusion monitoring device. The first successful attempts have been made to pharmacologically influence the plasticity of the human visual system.