Pathophysiology
Amblyopia is a developmental problem in the brain, not any intrinsic, organic neurological problem in the eyeball (although organic problems can lead to amblyopia which can continue to exist after the organic problem has resolved by medical intervention). The part of the brain receiving images from the affected eye is not stimulated properly and does not develop to its full visual potential. This has been confirmed by direct brain examination. David H. Hubel and Torsten Wiesel won the Nobel Prize in Physiology or Medicine in 1981 for their work in showing the extent of the damage to ocular dominance columns produced in kittens by sufficient visual deprivation during the so-called "critical period". The maximum "critical period" in humans is from birth to two years old. Diagnosis
Amblyopia is diagnosed by identifying low visual acuity in one or both eyes, out of proportion to the structural abnormality of the eye and excluding other visual disorders as causes for the lowered visual acuity. It can be defined as an interocular difference of two lines or more in acuity (e.g. on Snellen chart) when the eye optics are maximally corrected. In young children, visual acuity is difficult to measure and can be estimated by observing the reactions of the patient when one eye is covered, including observing the patients ability to follow objects with one eye. Stereotests like the Lang stereotest are not reliable exclusion tests for amblyopia. A person who passes the Lang stereotest test is unlikely to have strabismic amblyopia, but could nonetheless have refractive or deprivational amblyopia.
Furthermore, the effects of this kind of therapy may be further enhanced by noninvasive brain stimulation as shown by a recent study using anodal tDCS.A 2014 Cochrane review sought to determine the effectiveness of occlusion treatment on patients with sensory deprivation amblyopia, but no trials were found eligible to be included in the review. However,  good outcomes from occlusion treatment for sensory deprivation amblyopia likely rely on compliance with the treatment. References
Further reading
External links

National Eye Institute (NEI) Resource Guide
Lazy Eye Site from the National Health Service, UK
Look After Your Eyes - patient information on Amblyopia or lazy eye by College of Optometrists