Bulging Eyes

Bulging eyes is more of a symptom rather than a disease in itself. Protrusion of eyes anteriorly out of the orbit is also known as exophthalmos or proptosis. The protrusion of eyes can either be unilateral, that is, affecting only one eye, or bilateral, that is, affecting both eyes. The onset of this condition may be sudden or slow in nature. The amount of protrusion from the eyeball can be measured using an exophthalmometer. Complete or partial dislocation of the eye from the orbit is also possible due to trauma or swelling of surrounding tissue resulting from trauma. If this symptom is left untreated, then it can cause failure of the eyelids to close during sleep, which could lead to corneal dryness and resultant corneal damage.

What Causes Bulging Eyes?

Graves' Disease
One of the most common cause is Graves' disease. This is an autoimmune disease where the thyroid gland is excessively enlarged in a diffuse manner, producing large amounts of thyroid hormones. There are many systemic changes produced as a result of this condition, and these changes are caused by autoantibodies to the TSH-receptor that activate that TSH-receptor, thereby stimulating thyroid hormone synthesis and secretion and thyroid growth. The autoantibodies that are present in the blood target the fibroblasts in the eye muscles which can differentiate into fat cells. Fat cells and muscles expand and become inflamed while veins get compressed and are unable to drain fluid causing edema and protrusion of the eyes out of the socket. Thus, in the case of Graves' disease, the displacement of the eye is due to abnormal connective tissue deposition in the orbit and around the extraocular muscles which can be visualized with the help of a CT or an MRI scan. Along with bulging eyes symptom, there are many other Graves' disease symptoms, all of which are similar to the symptoms seen in hyperthyroidism.

Other Causes
Although Graves' disease is by far the most common cause of protruding eyes, there are many other conditions that can cause bulging eyes. Diseases that affect the eyes directly or indirectly can also lead to protrusion of the eyes. Cancer or tumors can lead to protrusion of eyes. This is especially the case with unilateral bulging of eyes. This signifies that there is a possibility that there is a cancerous growth present. Eye cancer is relatively rare, with retinoblastoma being the most common type of eye cancer. The second most common type of cancer is melanoma. Glaucoma is a serious disorder which is characterized by an increase in the pressure inside the eyeball. This could lead to enlargement and protrusion of eyes outside the socket. Hemorrhage or bleeding behind the eye can lead to bulging of the eyeball. Certain eye infections can also lead to inflammation of the eye, causing bulging eyes. Sometimes, a physical injury, like a head injury, can lead to bleeding behind the eye, causing protrusion of the eyes. Even an orbital fracture could lead to protrusion of eyes. Other possible symptoms of a head injury include headache, altered levels of consciousness, bleeding from the nose and ears, etc. This is an emergency condition and needs to be dealt with immediately. Other relatively rare conditions that can lead to bulging eyes include:

• Leukemia
• Eye problems like orbital cellulitis
• Meningioma
• Dacryoadenitis
• Mucormycosis
• Duane syndrome
• Carotid cavernous fistula
• Hemangioma
• High altitude cerebral edema

Although this is merely a symptom and not a disease in itself, it is important to take this symptom seriously. This is because process that is causing the displacement of the eye may also compress the optic nerve or ophthalmic artery. This could eventually lead to partial or complete blindness which may even be permanent.