Hi memememe (nice nick)
Here's how I explain the pain to people, might help clarify things with your partner.
Have him think back to when he had a muscle cramp in his calf muscle, most people have had at least one in their life.
Then, ask him to double that amount of pain, and have him think about how when a muscle cramp starts, it starts out of the blue with no warning. And then, for the 30 seconds or a minute that it lasts, it is all you can think about. It is an all consuming pain, nothing else exists but the muscle cramp.
Then, have him double the pain level again.
Then, shrink it down to where the pain would fit in his palm, but maintain that same intensity. Now, ask him to imagine that in his eye and lasting for 3 hours.
Mox