Neuroglia evolved after neurons did. The evolution of glial cells coincided with increased complexity of the organization of the nervous system.
Glial cells are supportive cells for neural tissue. As such, evolution of glia before neurons would not be a parsimonious hypothesis, however not impossible.
Glia indeed seems to have evolved ...
Demyelination per se is not the whole story behind the blurring of vision seen in MS patients.
MS results in an inflammation of the optic nerve (optic neuritis) and demyelination of the optic nerve fibers. It is commonly seen in MS, and is associated with blurred vision, basically because the signals are not sent properly along the optic nerve. Blurred ...