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Diameters of the three concentric circles are 1, 3, and 6 mm from center to outer circle respectively. Areas represented are the foveola (A0), the center of the fovea (B0; diameter = 1000 microns); the nasal, superior, temporal, and inferior quadrants of the parafoveal area (A1-A4; diameter = 3000 microns); and the nasal, superior, temporal, and inferior quadrants of the perifoveal area (B1-B4; diameter = 6000 microns).
