Probability Maps for Evaluating Automated Visual Fields

A computer system has been devised for the Octopus 2000R automated perimeter to transmit, analyze, display, and print statistical evaluations of visual field data. By using this system and its specific programs, three graphic displays have been devised to determine probabilities and directions of changes of visual fields. With an initial visual field, such as that using program 31, a probability contour plot is obtained in comparison to a reference population to determine by probability level whether the visual field has significant areas of abnormality. Two approaches can be used to indicate whether there is a change with visual fields over time: paired t test and regression analysis. If a paired t test is appropriate, selected areas of visual fields are compared to obtain a probability area plot. The t values and their probabilities are combined to obtain a three-dimensional plot indicating direction and significance. A similar procedure is used for a regression analysis: a contour plot of the probability values associated with the slopes of the regression lines is displayed. The slope values and their probabilities can be combined into a three-dimensional graphic display to indicate significance and direction of change. These graphic displays can provide a data analysis of visual fields that is easily visualized and clinically useful.