Lovely veiled boy. What supplements are you using, and what is your current supplementation schedule like? I’m also curious as to what you’re gutloading your feeders with, and what is your misting schedule like? Rubbing the eye along branches and rolling it under the eyelid means your chameleon‘s eye is feeling irritated. He may be trying to clean it. Could be a piece of shed, some soil from one of his plants or a piece of branch caught in there. A daytime misting of 2-3 minutes may give him the opportunity to flush and clean the affected eye out. If it continues, I’d look at supplementation next and probably get him to an exotic vet.
The first thing I thought to ask about was supplementation because I experienced a similar issue with one of my panther chameleons. He was very obviously experiencing irritation in one eye, and I caught him rubbing it along branches frequently. He would also close that eye a lot and roll it around within the turret. I hadn’t kept a chameleon in years and forgot a lot of important stuff, like what supplements to use. Many things about basic husbandry had also changed, so the information I found when I got my first panther was pretty different. I messed up and purchased Herptivite with beta carotene, no preformed A. My guy wound up with a vitamin A deficiency because of it and that caused the irritation in his eye. He made it worse by rubbing it on branches. He then began experiencing the same problem in the other eye, and I took him to the vet. I ended up completely switching from Herptivite to Repashy LoD. I use that as an all-in-one for both his D3 and multivitamin.
I hope your boy feels better soon!
I really have wanted to do right by him and give him all I can. 
