Systematic reviews and randomised controlled trials on open angle glaucoma.

Evidence for the effectiveness of interventions to prevent the progression of optic nerve damage in open angle glaucoma has evolved over the last 25 years. We describe that evolution through the systematic reviews on various aspects of the topic and how those reviews have highlighted the need for new trials. Though we can be confident that lowering pressure does indeed reduce the risk of progression, we still lack good evidence on the comparative effectiveness of different treatments not so much on lowering pressure but on preventing progression of the disease. This is true for different medicines, types of laser and especially for different surgical interventions. As always there is a need for more research, but this needs to be focussed on key uncertainties using core outcome sets which avoid research waste. Ultimately, our guidelines can be based on sound and comprehensive evidence of effectiveness.