In previous papers1 diagnostic scales were published for the form and color fields based on the area and the average breadth of field in the eight principal meridional quadrants. The average breadth of field was expressed in terms of the distance of the limit in degrees from the center of the field. The area of the field was obtained by plotting the field on a scale of 12 mm. to 10 degrees and measuring the area of the plotted field in square centimeters by means of a planimeter.
Data treated in this way are serviceable primarily in cases in which the contraction produced by the pathologic condition is more or less regular or when an irregular contraction is of sufficient magnitude to affect substantially the area of the field or the average breadth of the field in the eight meridional quadrants.
For the reason that not all irregular contractions