Michael Garin O.D. Proptosis, or exophthalmos, is the bulging out of one eye (unilateral) or both eyes (bilateral). Cases of proptosis develop for reasons ranging from variations in our anatomy to the development of another condition such as hyperthyroidism, of which bulging eyes are a symptom. If a person suddenly develops exophthalmos, especially in both eyes, it is considered a very serious problem. Sudden onsets of proptosis should always be evaluated by an eye doctor immediately. In mild cases of proptosis, a doctor can take measurements with a special ruler known as an exophthalmometer. If measurements are within a certain range, more testing is unnecessary.