I'm not by any means a vet or expert... especially on veileds. That being said, I noticed what appear to be a few other issues that may be causing this "eye issue". Can't really make out much from the photos... but this is what I came up with:
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The red circle definitely looks like some for of abscess, visible from the picture of the front on look.
Orange circle - the lips aren't meeting properly and you can see the gum line. No good.
Blue circle - I couldn't really tell from any of the photos, is this a "bump" or just a weird photo angle?
I also noticed the crown has a jog in it, but that looks to be old trauma. Do you have any better photos, preferably of the whole cham?
Definitely be sure to fill out the form Beman posted... I noticed a lot of debris in your cage which is usually not recommended for chams as they tend to ingest random stuff thought the cage. Debris also leads to bacterial/fungal/insect growth unless you have spot on bio active substrate and proper drainage. [All the more reason to fill out the form]
I guess it's a moot point as you're already going to the vet... but I'd be sure to gather as much info as you can to point the vet in the right direction.
Best wishes!