What is wrong with my cat

As you can see Norman has a very swollen right eye with quite a bit of discharge.    This is his third time in 6 months for his eye to have these symptoms.  I call our vet to schedule an appointment but his face goes back to normal before I can get him to see the vet in a day or two.   He acts, eats and drinks just fine.   At first I thought he was stung by a wasp or scorpion.   Our house is exterminated so we do not have issues with insects.   We have another cat be he is the dominant cat and the other cat is not aggressive.   Any thoughts.  

Poor guy! Can you show this picture to your vet when you bring him in? I would definitely make an appointment.

Can you email the picture to your vet now for review so he / she can be prepared for the upcoming appointment or even reschedule you for a sooner appointment? Since this has happened before, the vet should get a picture of the eye issue before it clears up again.

You also might want to find out exactly what your exterminator used to bug-proof and scorpion-proof your house.  The vet might ask. This doesn't look like any indoor cat problem I've ever seen.   I hope you can get in to see your vet asap; this looks very painful.  Poor little guy!  Please keep us updated.

His eye is already 80% better.  It's the grassiest thing.    It comes and goes quickly but looks real bad.  But yes I will send the vet the photo.  His appointment is scheduled for next week.