The disease is caused by producing too much of a protein needed in myelin, which then becomes stuck inside the cells.

BBC: Nerves

He developed an antibody to an unknown protein in the myelin.

FORBES: Magazine Article

The retinal nerve fiber layer is the one part of the brain where nerve cells are not covered with the fat and protein sheathing called myelin, making this assessment specific for nerve damage as opposed to brain MRI changes, which reflect an array of different types of tissue processes in the brain.

CNN: Can an eye exam detect multiple sclerosis?