Research evidence from systematic or literature reviews is displayed in a matrix. The columns show thematic areas that are relevant to the theme of cataracts, labelled as sectors and sub-sectors. The rows show the strength of the evidence in each review: strong, inconclusive, or weak.  If the authors of a particular review were able to reach a conclusive answer to their research question using the evidence available, the evidence is classed as strong. If they were unable to answer the question given insufficient evidence, evidence is classed as weak. If the outcome was somewhere in between, the evidence is classed as inconclusive.

• By clicking on the ‘Overview’ tab, you can see at a glance where the 86 reviews relating to cataract fit within the matrix.
• By clicking on the ‘Details’ tab, the added detail of their methodological quality is displayed on the gap map itself.

The numbers displayed in each box indicate the number of systematic or literature reviews in each sub-sector. The boxes ‘fill up’ depending on how many reviews are available. By hovering over a number and clicking on it, you can see the full hyperlinked list of reviews. The reviews are split by confidence level, which is an indicator of the methodological quality of the reviews themselves. We have rated the methodological confidence in each review as high (green hexagon), medium (yellow square) or low (red circle). By clicking on one of the hyperlinks, you will be taken to a separate webpage to read a summary of that individual review.