Amblyopia, or more commonly lazy eye, is poor vision in one or both eyes due to a lack of stimulation to the retina (the back inside surface of the eye that relays information to the brain) during the critical development period in childhood (from birth to around 7 - 8 years of age).
Common underlying causes of a lack of stimulation include squint (misalignment of the eye), uncorrected refractive error (e.g. long-sightedness or astigmatism), ptosis (droopy upper eyelid obscuring the pupil) and cataract.
It is very important that amblyopia is detected early (approximately before the age of 7 - 8years) in order to try to improve the weak vision. If amblyopia is not detected before this critical age, treatment is less likely to be effective.