Technical note. Conversion of planimetric visual field data into solid angles and retinal areas

This paper presents a convenient method to convert perimetric maps into solid visual field angles and retinal areas; this problem has been addressed previously, but conversions in a tabulated form were not available. The distortion in conventional perimetry charts is discussed, and previously presented solutions, aimed at faithful rendition of either contour shape or area, are reviewed. The optical geometry connecting coordinates in a perimetry chart to corresponding points in the visual field and in the retina of a schematic eye is presented, and tables for computation of solid field angles and retinal areas from contours in the cart are given. The range of applications for this correction of perimetry data and some of its limitations, such as interindividual variability of ocular dimensions, are discussed. In the Appendix, a convenient way to use the tables for qua ntitative visual field analysis is presented.