Figure 5.

Illustration of optical transfer function manipulation conditions to estimate only the effects of contrast demodulation of the two eyes' images. Point-spread functions (PSFs) for high-order aberrations were derived for three manipulations: (1, top row) native modulation (modulation transfer function) and phase (phase transfer function, PTF), (2, middle row) after setting the PTF to zero to remove phase distortions, and (3, bottom row) after making the modulation transfer function symmetric across all orientations in addition to setting the PTF to zero. Since the phase governs the final shape of the PSF, setting the PTF to zero makes the new PSF mirror symmetric in the middle row, and making the modulation transfer function symmetric makes the new PSF rotationally symmetric in the bottom row. In the third symmetrized condition, the PSF has the same shape across eyes and conditions, while allowing contrast to remain at its original value for individual eyes. Differences in the PSFs between eyes would reflect the influence of contrast.