Are permanent effects of hyperthryoidism bulging eyes?

Yes: If the swelling and inflammation behind the eyes causes damage to the optic nerve (nerve from eye to brain), the damage can be permanent. Sometimes the changes in the muscles around the eyes can be permanent as well (this can be repaired with surgery usually). If treated appropriately and quickly, the swelling usually goes away!

Permanent effect: Bulging eyes or proptosis can be a permanent effect of Graves' disease. It depends on the severity and duration of the disease. Some mild cases of bulging will improve after the Graves' disease is treated. More severe cases may require 1 to a few surgical procedures to reset the eye balls in their sockets.