Graphical analysis of topographical trends (GATT) in automated perimetry.

The assessment of change in analysis of visual fields is one of the most difficult tasks in automated perimetry. A new, computerized method shows the original fields and the topographic trends in one easy graphic display. This new way of analysis the 'GATT' superimposes the grayscale maps of two fields with a simple logic, producing the following patterns: all stable, unchanged areas are displayed normally; in changed areas, the grayscale of the first and the second field are mixed in the form of stripes. The contrast between the stripes indicates the amount of change. The orientation of the stripes depends on the direction of change: horizontal stripes mean deterioration, vertical stripes mean improvement. The GATT is also able to compare 4 fields, using the same patterns. In addition, a scatterboard without stripes indicates areas of high fluctuation, but without a significant change in the course of the 4 fields. The GATT enables a quick, quantitative judgement of the trends of visual fields.