Just a hint.... check everything you eat and make sure
you are not getting any MSG food additive. This can trigger the NMDA pain receptors and at least for me, I get blurred vision from it too. I can always tell if it has sneaked in thru restaurant food.

http://www.msgtruth.org/

Itching that comes and goes suggests that you are exposed to
"something" which is triggering it. Itching is a form of pain.

I'll put up this helpful graphic that shows the 4 types of nerve fibers of sensation:

Neuroscience For Kids - conduction velocity
according to this site, it is the "C" fibers which carry the sensation of itch.

And if you read this link carefully, you will see an explanation of the speed of each type of fiber. The fastest fibers can and do cover up the perception of the slow ones. And the C fibers are the slowest.
This is why you may feel C fibers the most when you are quiet, and not moving around.

PN is a complex condition, and in many cases, it is a result of the environment the person is exposed to. Foods, chemicals consumed, breathed in, or put on the skin, drugs, microbial infections and assaults, are often culprits in nerve damage.

There are genetic types of PN (CMT) which affect the mitochondria of the cells in the nerves. And there are metabolic causes...which are often alcohol and its congeners, diabetic types, and thyroid derangements, besides the environmental insults. This is why it is so complex to doctors and patients, to get help and relief.

Keeping a journal can be helpful. I will add that some skin products do contain gluten, and my son is especially sensitive to that situation.