I agree. I had that symptom sporadically back while I was trying to get diagnosed. The first time, I thought I was getting a migraine or maybe an ocular migraine.

Then I read about people with MS having ON and losing their sight, and it scared the tar out of me. However, my ophthalmologist said my optic nerve looked perfectly healthy, and it still does.

I don't get it very often anymore, and that's probably because I try not to get overheated or overexert myself.

Even though I now know what it was/is (in my case), it's still an unsettling feeling.