From the related links in this article, I learned that Visual Snow[1] is not what everyone sees at nighttime or when they close their eyes, as I have, for as long as I can remember. I just figured our eyes cranked their ISO sensitivity up.<p>[1] <a href="https://en.wikipedia.org/wiki/Visual_snow" rel="nofollow">https://en.wikipedia.org/wiki/Visual_snow</a>
Another interesting phenomenon is seeing white blood cells swishing through the capillaries in front of the retina[1]. They are most noticeable looking at the blue sky on a sunny day.<p>[1]: <a href="https://en.wikipedia.org/wiki/Blue_field_entoptic_phenomenon" rel="nofollow">https://en.wikipedia.org/wiki/Blue_field_entoptic_phenomenon</a>
Fun fact: "Eigen-" is the same word part as in "eigenvalue", "eigenvector" or "eigenfrequency", meaning intrinsic/inherent to.