In the present study, according to the $Q$-value of each semimeridian in the near-horizontal regions, including 0 deg to 50 deg, 130 deg to 180 deg, 181 deg to 230 deg, and 310 deg to 359 deg, the 360-semimeridional variation of the $Q$-values for each subject was modeled by polynomial fitting with MATLAB (MathWorks, Inc., Natick, Massachusetts). Then, we fitted the $Q$-value of each semimeridian in the near-vertical regions, including 51 deg to 129 deg and 231 deg to 309 deg. The polynomial function took the form $f(x)=p0+p1x+p2x2+p3x3+p4x4+\u2026$, where $x$ is the semimeridian angle $\theta $ (deg) and $f(x)$ is the corresponding $Q$-value. The degree was converted to a radian when we performed the polynomial fitting.