Using a screening programme at a frequency of every 3 years, the CE estimate was Can$100,000 per year of blindness avoided, and 354 cases per year were avoided when patients aged 40-79 were included, the participation and compliance rates were 75%, and efficacy was 50% (scenario 1). The CE estimate was Can$36,000 per year of blindness avoided, and 209 cases per year were avoided when patients aged 65-79 years were screened every 3 years, participation and compliance was 75%, and efficacy was 50%. The CE estimate was Can$208,000 per year of blindness avoided, and 354 cases per year were avoided with a screening programme identical to scenario 1, carried out yearly.