Proptosis and exophthalmos are terms that refer to bulging or prominent eyes. While it is true that an underlying medical condition such as hyperthyroidism (caused by Grave’s disease) can cause proptosis, many other factors can lead to prominent eyes. Some people are born that way, with eyes that protrude more than usual. Other causes of bulging eyes include leukemia, lymphoma, neuroblastoma, hemangioma, orbital cellulitis, and rhabdomyosarcoma. Bleeding behind the ear due to injury, connective tissue diseases such as sarcoidosis, and metastatic tumors may cause bulging eyes. It's best to consult your eye doctor to rule out any serious ailment like cancer.