Aim: To estimate the prevalence of primary angle closure glaucoma(PACG) in European derived populations. Method: Systematic reviewand modelling of PACG prevalence data from population studies. PACGwas defined according to the ISGEO definition requiring structuraland/or functional evidence of glaucomatous optic neuropathy. Prevalenceestimates were applied to the 2010 United Nations projected populationfigures to estimate case numbers. Results: The prevalence of PACGin those 40 years or more is 0.4% (95% CI 0.3% to 0.5%). Age-specificprevalence values are 0.02% (CI 0.00 to 0.08) for those 40-49 years,0.60% (0.27 to 1.00) for those 50-59 years, 0.20% (0.06 to 0.42)for those 60-69 years and 0.94% (0.63 to 1.35) for those 70 yearsand older. Three-quarters of all cases occur in female subjects (3.25female to 1 male; CI 1.76 to 5.94). Conclusion: This analysis providesa current evidence-based estimate of PACG prevalence in Europeanderived populations and suggests there are 130 000 people in theUK, 1.60 million people in Europe and 581 000 people in the USA withPACG today. Accounting for ageing population structures, cases arepredicted to increase by 19% in the UK, 9% in Europe and 18% in theUSA within the next decade. PACG is more common than previously thought,and all primary glaucoma cases should be considered to be PACG untilthe anterior chamber angle is shown to be open on gonioscopy.