A commercial statistical analysis software package (SPSS, ver. 14; SPSS, Chicago, IL) was used. Another commercial graphic software package (SigmaPlot, ver. 8.0; Systat, San Jose, CA) was used for graphic analysis. Independent samples t-test or paired t-test, as appropriate, were used to investigate the differences between various groups, depending on the analysis in question. The association between the MP spatial profile types and foveal widths, controlling for sex, was investigated using a general linear model approach. We used the linear model; y = b0 + b1 × 1 + b2 × 2; where y is foveal width, x1 is indicator for group (typical/secondary peak) and x2 is indicator for sex. This model tests whether group membership is related to foveal width, when adjusted for sex and vice versa, and whether sex is related to foveal width, when adjusted for group membership. Piece-wise linear approximations to each subject’s foveal pit profile, at eccentricities of 0.25°, 1°, and 1.75°, provided FPPS data, which were then used to investigate the relationships between subject’s MPOD and foveal pit profile. Pair-wise correlations between MPPS and FPPS were calculated, and differences in mean FPPS between group 1 (typical MP spatial profile subjects) and group 2 (secondary peak profile subjects) were assessed using the independent-samples t-test.