Support research and public health
One of the group’s aims is to make the process of sourcing data (systematic review) and the statistical modelling process as transparent as possible so that it can be understood by a multitude of individuals. The methodology for these papers has been published in scientific journals but has also been described in more simple terms in a powerpoint presentation accessible from this website.
As with any attempt to draw conclusions from multiple studies, there are limitations to the estimates such as representativeness of populations by individual studies, survey response rates, and methods used to measure visual acuity. These are all described in the above links.