Possibly a Vitamin A deficiency?? Check his diet
My past Panther died of a Vitamin A deficiency because he was on a bland diet of giant mealworms and crickets(that were probably not gutloaded enough). Same symptoms....His one eye stayed shut but everything else seemed O.K for awhile. I did bring him to see an Exotic Vet but was unfortunately misdiagosed as possibly having an URI. She precribed Baytril anyway even though she admitted he didn't show any symptoms of an URI and on top of that, she examined his eye and stated it looked fine and told me that he was in overall O.K health. To make a long story shorter, my Panther died 4 months later(his health started declining rapidly) and he was was getting very weak and loosing his sense of balance and then he ceased eating and drinking completely. He died at 11 months.
Now, I have an 8 month old Veil and he eats a healthy chunk of of Collard Greens leaves which is high in Vitamin A and in addition, silkworms that supply him with extra nutrients due to the mulberry mash that they eat. I have definitely learned a lot from being on this forum and when my Panther started getting real weak and lethargic, that was when I initially searched out for this type of a forum to get advice and feedback. Wished I had found this forum sooner to get the invaluable information that I needed at that critical time and could have reversed the vitamin A deficiency effects so my Panther possibly could have been saved.
What does his diet consist of on a daily basis? I know that when a Chameleon's one eye is shut for that long of a period and it's not because there's anything irritataing his eye, I would check that he's getting enough of the real natural Vitamin A in his diet(Not the synthetic vitamin supplement powder that you dust their insects with).
Christine