The concept of visual field indices.

Statistical methods for the evaluation of quantitative visual fields are presented in addition to a mathematical description of the calculation of different visual field indices. The "mean defect" is important for diffuse damage as well as for follow-up in advanced stages. "Short-term fluctuation" provides information about the reliability of the results as well as about possible early damage. "Corrected loss variance" quantifies local defects in an early stage; it also separates real local defects from increased scatter. "Skewness" is a test for very early local defects, and "spatial correlation" provides a measurement of the clustering of any local defects that may be present.