Eye in thyrotoxicosis. Side view of a bulging eye (exophthalmos) in an elderly woman with Graves' disease. Graves's disease is a form of thyrotoxicosis (overactive thyroid gland). Bulging eye is caused by swelling of soft tissue in the bony orbit (eye socket). The eyeball is pushed forwards forcing the eyelids apart, creating a staring appearance. Bulging eye may also be caused by a tumour, inflammation & aneurysm (swollen artery). It can restrict eye movement and cause double vision. The pressure in the orbit can restrict the blood supply to the optic nerve causing blindness. Treatment includes surgery, and usually also the thyroid disorder.