What neurological mechanisms cause shimmering and wave-like visual distortions after sustained focus?

After sustained visual fixation on a nearby point (such as the tip of the nose) followed by shifting gaze to empty space, some individuals report visual distortions—such as shimmering lights or mirror-like glowing effects—even under normal lighting.

Over time, these effects begin to occur automatically. The shimmering appears like mirror-shining light and wave-like patterns that follow wherever the eyes move—whether near or far—while vision remains otherwise clear.

What are these visual phenomena, and why do they occur? How does the brain or visual system generate these effects after prolonged fixation? I’m looking for a scientific explanation from a neurological or visual processing perspective