Kinetic perimetry is still a widely accepted and used means of assessing the visual field. Attempts at quantifying the area of vision for given isopters have been limited to area measurements on visual field charts, which are azimuthal equidistant polar map projections of the inside surface of the perimetry bowl. Such measurements distort the true size of scotomas (or seeing areas) when the boundaries measured are farther from the center of the field on the chart because of cartographic distortion inherent with this projection. We believe that the solid angle in steradians subtended by the scotoma or the seeing area is a more appropriate measure of the visual field than area on a flat representation. We used a simple computer program to determine the solid angle for given isopters of graphed perimetric visual field data.
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