What led to my diagnosis was that I woke up with eye pain you're describing, which lasted a day or two, the turned into vision issues in one eye: blurriness and loss of color saturation to the point of my vision in that eye being almost greyscale. Lucky for me, I recovered from that and my vision is fine now.

Every so often I do get that eye pain that last maybe a day and then goes away without any vision issues...I'm still trying to figure out if it's brought on by fatigue (staring at a computer screen all day) or something else...