Exophthalmos or "Pop-eye" can be from a range of causes ranging from injury to infection and tumour behind the eye.
To be on the safe side separate the fish and treat with salt . Some times the swelling will subside but the eye will probably be lost.
Bruce Hansen
<<Hi all. I have a P. signifer that all of a sudden has its left eye
protruding from its head about 2-3mm. Is this a disease, i read
tuberclorosis can cause something like this, or could this be an
accidentthat the fish got into.>>