OCT was performed with the ultimate commercial OCT units (OCT3, Carl Zeiss Meditec, Inc, Dublin, CA) to measure the macular thickness under papillary dilatation by an experienced examiner. The retinal thickness was calculated using OCT retinal mapping software (version 6.1 a), which measured thickness of nine divided macular regions after six scans with 6 mm long centered on the patient's fixation point by means of an inner fixation target (Figure 1), and expressed as a color-coded map. Internal fixation was essentially chosen due to better reproducibility. We defined the foveal area as the area centered at fixation with a diameter of one millimeter, the inner ring as the area between circles with diameter of one and three millimeters, and outer ring as the area between circles with diameter of three and six millimeters (Figure 2).