How visual impairment evidence gap maps are constructed

These visual impairment evidence gap maps (EGMs) have been developed  by a team of researchers from Sightsavers, the Cochrane Eyes and Vision Group and the International Centre for Eye Health at the London School of Hygiene and Tropical Medicine, drawing on the guidance and previous experiences of the International Initiative for Impact Evaluation (3ie), which initiated the development of EGMs.

The development of EGMs followed a standardised systematic process:

• First, electronic databases were searched for all systematic and literature reviews published since 1993.
• The retrieved abstracts of the reviews were screened against a pre-defined list of inclusion criteria and the relevance of evidence to low and middle income countries was assessed by eye care experts with significant experience in these settings. The methodological quality of the reviews was assessed using an adapted version of the SURE checklist. To ensure the process was fair and unbiased, two people independently appraised each review and a third reviewer arbitrated in the cases of disagreement.
• The process resulted in a short document summarising the review, its findings and methodological quality. The appraisals and summaries were shared with the corresponding authors, who had an opportunity to provide feedback and respond to methodological queries.

EGMs were produced by constructing matrices, where review focus areas are displayed along the x axis, and the strength of evidence is shown along the y axis.

The cells where no reviews are shown indicate the areas where more evidence is required and where future research efforts should be directed.