I was wondering if anyone has found that eye pain is a symptom of SM?

Sammy has been on 5mg prednisone every other day for SM for 5 years. He has done amazingly well for all that time with very few symptoms despite having been in a really bad state when he was young (gabapentin wasn't enough).

About a week ago, however, I noticed him squinting his right eye quite a bit. I gave him some gabapentin that I keep in case of pain episodes and it seemed to help. He was then fine the rest of the week. But today I came home from work and both of his eyes were half closed. He was still energetic and tail-wagging but clearly in some pain. I gave him 150mg gabapentin and again it helped (though it's also made him drowsy).

I'll take him to the vet soon, but I wanted to find out if others have experienced this kind of eye pain as part of SM? Could it be a sign the SM is finally getting worse? Prior to prednisone his symptoms were scratching like crazy, chewing his paws and rubbing his head frantically.