The authors conducted this study for systematic assessment of the literature to provide an estimate of the global and regional prevalence of amblyopia, to determine the trend of its prevalence in previous years, to explore the factors contributing to differences in its prevalence and to understand the causes of amblyopia. The review found 1252 potential studies of which 73 were included; a total of 530,252 cases from six World Health Organization (WHO) regions. The global prevalence of amblyopia from this meta-analysis was 162-188/10,000. Prevalence differed across geographical locations with higher prevalence in the US and Europe than Asia and Africa. There was a lower prevalence of amblyopia in children than adults. Anisometropia was the most common cause. Strabismus and refractive errors were also common causes.